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Meteorology and climatology of the seasonal sea ice zone
134 METEOROLOGY AND CLIMATOLOGY OF THE SEASONAL SEA ICE ZONE R.G. BARRY I n s t i t u t e of Arctic Boulder 80309
and Alpine Research and Department of Geography,
University of Colorado,
INTRODUCTION The extent of the seasonal sea ice zones (SSIZ) in both hemispheres is delineated in Figures 1 and 2 which show the range between the average seasonal maximum and seasonal minimum for ~ i/8 concentration.
A marginal ice zone (MIZ) contiguous with the open ocean represents
one general type of SSIZ, but in Antarctica this is circumglobal extending more or less concentrically around the continent between latitudes 600 and 70°S.
The ice varies greatly in
area between September and March, from about 2.5 x 106 to 20 x 106 km2.
In the northern hemis-
phere, in contrast, there is marked longitudinal asymmetry and the seasonal range is much less, from 7.0 x 106 to 14.1 x 106 km2 (Walsh and Johnson, 1979) due to the land-sea distribution. While the maximum l i m i t of the MIZ extends to south of 50°N in the Sea of Okhotsk and the Labrador Sea, there is open water to the north of 75°N in the Norwegian-Barents Sea. From a meteorological
standpoint,
these MIZs are not
subject to an unlimited
fetch of wind and
currents such as occurs around Antarctica and should, therefore, be regarded as a second type. A third type of SSIZ is represented in the essentially closed Arctic Ocean where the winter extension of the pack ice is constrained by land and shorefast ice, creating shear zones. These are prominent features from the Queen Elizabeth Islands to the Beaufort Sea coast of Alaska. The most extensive SSIZs in the Arctic occur in the Barents-Laptev and Chukchi-Bering "shelf seas". Since the SSIZ is defined by the seasonal range of ice limits, terization is not readily described in a systematic manner. solely determined by meteorological
its meteorological
charac-
Moreover, the ice limits are not
factors, nor does the SSIZ set up a unique climatological
regime. Accordingly, this survey reviews selected aspects of large-scale circulation processes and examples of specific regional
interactions, based on the available l i t e r a t u r e .
Problem
areas are then identified.
AII4OSPHERIC CIRCULATION CHARACTERISTICS Comparison between the summer ice l i m i t in Antarctica and circulation parameters shows that the polar front is located about 45°S and although there is a subsidiary maximum of 1000,500 mb thickness gradient at 70°S there is no strong evidence for a climatic front (Taljaard, 1972, Fig. 8.9).
In addition, in winter the frontal
zones are separated from the pack ice margin,
except perhaps where the ice reaches farthest north to latitude 55°S in the South Atlantic. The situation is well summarized by Van Loon (1972, p. 67) who states:
"In the transition
seasons when the mean position of the circumpolar trough is nearest Antarctica, the border of
135
120°
90°E
60 °
150°
180°
150°
120°
Figure I.
90°W
60 °
Northern Hemisphere SSIZ (after CIA, 1978)
the ice is near i t s extreme poleward and equatorward positions.
In the months when the trough
on the average is farthest north, the ice border has reached no such extreme position."
The
frontal maxima, especially in the South Atlantic and South Indian Oceans are instead closely related to sea surface temperature gradients associated with the Subtropical
and Antarctic
Convergences. There is, nevertheless, a close seasonal relationship between the ice margin and the latitudinal
band of maximum cyclone frequency in the transition
Schwerdtfeger and Kachelhoffer (1973).
seasons according to
This is examined further below.
In the northern hemisphere the three areas of extensive winter ice; the Bering-0kh~tsk Sea,
the eastern Canadian Arctic and Subarctic, and the Barents Sea, are all located close to mean January and April 700 mb pressure troughs.
The mean contours indicate advection of cold north-
westerly air streams on the western side of these troughs.
In contrast, the longitudes
of
136
30 °
0o
30°
I EXTENT OF SEA ICE ~> 1/8 CONCENTRATION
60° 60°
~OUTH
90°W
J,POLE
90OE
120° ~'-/0
~
~
/M~oluteMin.
120°
~eters~ 150°
180°
Figure 2. Scandinavia,
Alaska,
150°
Northern Hemisphere SSIZ (after CIA, 1978)
and to a lesser extent Greenland, are sectors where, particularly
spring, there are maxima of blocking ridges (Rex, 1950).
In winter the mean polar frontal
zones are well south of the ice margins but there is a secondary ' a r c t i c ' eastern North Atlantic.
in
front in the north-
A major depression track from Newfoundland to Iceland parallels the
ice margin (Klein, 1957), although i t is displaced southward 80-90 latitude.
In summer, the
arctic front l i e s over the forest-tundra ecotone on land (Reed, 1960; Bryson, 1966; Krebs and Barry, 1970), but there is a secondary cyclone track along the Arctic coasts of Siberia and Alaska both in summer and in fall
(Klein, 1957).
137 ATMOSPHERIC CIRCULATION/ICE FEEDBACKS This topic
has been approached by descriptive synoptic case studies and by simulation
experiments with circulation models.
Potentially,
budget calculations on a synoptic basis.
it
also requires examination via energy
For Antarctica, the dramatic seasonal expansion and
contraction of the sea ice has been explained by Gordon and Taylor (1975) in terms of (1) the Ekman divergence due to the curl of the wind stress, and (2) the surface heat balance.
The
f i r s t factor is associated with cyclonic activity, while the second is related to open water areas in the case of the summertime decay of the pack. They suggest that with a more northern location of cyclonic activity there would be more ice cover and, therefore, reduced upwelling, in turn limiting summer melt and hence lessening the seasonal fluctuation. The extent to which storm activity may cause a positive feedback between atmosphere and sea ice has been examined by Ackley and Keliher (1976).
A rapid decrease in sea ice in the
Bellingshausen Sea in 1973 is thought to have caused a relative gain in atmospheric heat, thereby augmenting cyclone activity which in turn helped to maintain less ice cover.
Figure 3
illustrates the anomaly of atmospheric heat loss in 1973, which may have been up to an order of magnitude greater
than the average total
energy of a midlatitude cyclone (2.1 x 1016Kj).
Ackley and Keliher propose that usually the ice concentration is sufficient for storm activity to cause its convergence, reducing the sensible heat flux and thereby increasing the net atmospheric heat loss.
However, poleward flow of warmer air, with meridional blocking patterns, may
decrease the ice extent and its concentration.
Under such conditions, enhanced storm activity
could cause divergence of the pack. From averaged data, Budd (1975) indicates that a I°C increase in mean annual temperature corresponds to a 2.50 latitude change at latitude 60°S, suggesting a stable feedback relationship. 1 There is also a 70 day reduction in the duration of ice cover in Scotia Bay for an average 1°C warming. Budd suggests that more extensive ice may increase the meridional temperature and pressure gradients and, therefore, the zonal (westerly) circulation.
However, Miles (1975) demonstrates
for the North Atlantic that such a relationship does not hold on the 5-30 year time scale. Indeed, there may have been a slight increase in poleward sensible heat flux associated with the post-1930 decrease in zonal circulation (Miles, 1976). In the northern hemisphere, where the overall pattern of ice extent is strongly influenced by the interactive oceanic and atmospheric circulations, most investigations have been regional in character.
The causes of anomalies in ice extent in the North Atlantic sector 2 have been
IA 10 latitude change in the ice l i m i t represents a change of about 15 percent in hemisphere sea ice cover (Streten, 1973).
138
0 ~
,,
,
,I
,
'
i
I
,
l
,
r
l
I.
•
.
.
.
.
J
r U
50
01
i
i
l
#s,io~,,,
oI
'~°~S
l,
+
I
i
l
+..tot.+
-'+
I
',:p, i+
+
•
,
1~t
,op p..m
+ Figure 3.
~
,
1
Ice pack characteristics, atmospheric heat loss, and n~mber of low days per week for Sector I (Amundsen-Bellinghausen) for 1973. (from Ackley and Keliher, 1976).
examined on synoptic to monthly time scales by many investigators (see Nusser, 1958; Bjornsson, 1969; Haupt and Kant, 1976; Vinje, 1977).
An analysis of anomalies off East Greenland by
Aagaard (1972) shows that when the late-winter/spring pressure pattern resembles the mean map, with a trough extending northeastward from the Icelandic Low, this generates cyclonic curl of the wind stress and northward retreat of the ice.
In contrast, in years with high pressure
over Greenland, there is southward current and ice transport due to the anticyclonic curl. According to Vowinckel (1963), 2/3 of the total ice export is due to the current and only I/3 to wind-induced export. He also shows from correlation analysis of ice extent between April and August, and August with the following April, that freeze and melt processes tend to dampen variations caused by ice import.
Since the influence of wind velocity may strongly influence
the ice margin on the time scale of a week (Einarsson, 1972) i t is important to ask whether this is long enough for major feedback effects on the atmosphere. From Ackley and Keliher's work, discussed above, i t would appear that a 10-day period is certainly sufficient for such effects to operate on a regional scale. 2Processes operating ni the Baltic Sea and Hudson Bay are rather special and are not discussed here. Schell (1964) has performed comparable investigations in the Sea of Okhotsk.
139 In the Bering Sea where the seasonal ice maximum approximates the edge of the continental shelf, the limiting control on ice extent is probably heat transport by the Pacific Current according to Dunbar (1976).
However, the role of northerly winds in spring 1976 has been
demonstrated by Muench and Ahlnas (1976).
They estimate that the mean observed southward
motion of 1.8 m s-1 would require a minimum heat loss of 42 Wm-2 for ice formation.
I f most
of the ice forms in divergent areas of open water and thin ice, this value would increase by an order of magnitude. The effects of sea ice anomalies on the atmospheric circulation has been examined empirically by Wiese (1924) and through a GCM experiment by Herman and Johnson (1978). Wiese showed that, in the North Atlantic, cyclone tracks are further south in years with heavy ice than in years with light ice.
This result has been confirmed by Herman and Johnson. Using the GISS
GCM, they compare a mean of two mid-winter
simulations with 'maximum' ice in the northern
oceans (corresponding to observed conditions) with the mean of six simulations with minimum mid-winter ice extent. circulation.
They demonstrate both local and hemispheric effects on the atmospheric
With maximum sea ice there is an increase of sea-level pressure over the ice and
a southward shift of cyclones in the North Atlantic, giving increased precipitation over northern Europe. coupled with latitudes.
On the hemispheric scale, deeper Icelandic and Gulf of Alaska lows at 700 mb are stronger
subtropical
anticyclones
and enhanced poleward energy flux
in mid-
Herman and Johnson note, however, that the model omits feedback processes, includ-
ing changes in sea surface temperatures. ENERGY BUDGETS The large-scale energy budget regimes of the Polar Ocean and adjacent seas are well known in broad terms from observational
and analytical studies.
In particular, Vowinckel and Orvig
(1966, 1970) and Vowinckel and Taylor (1965) have mapped calculated values for the whole area and distinguished several distinctive seasonal energy regimes. They identify the pack ice of the central tinental
Polar Ocean as a transitional
type, resembling oceanic areas in summer and con-
areas in winter and the transition seasons.
In the context of the SSIZ, the map
delimiting regions investigated shows that only the Kara-Laptev Sea area is essentially located within the SSIZ. Their analysis of the Norwegian-Barents Sea includes all the area north of 65°N, for example. Table 1 summarizes their results for the central Polar ocean and the KaraLaptev seas for annual totals and the extreme months.
Interestingly, the results for the
latter are consistently much closer to the central Polar Ocean than to their calculated values for the Norwegian-Barents Sea. Their calculations indicate that the evaporative heat-loss from open pack ice is very similar to that from an open ocean, except in summer months at 650/700 N and 700/ 750 N when there is evaporative heat loss over open water but a small heat gain to open pack ice (Figure 4).
140 Table 1.
Energy fluxes at the surface in the Arctic (Wm'2)(after ANNUAL Central Polar Ocean
JANUARY Central Polar Ocean
KaraLaptev Sea
.
JULY Central Polar Ocean
KaraLaptev Sea .
Vowinckel and Orvig, 1966)
.
KaraLaptev Sea
S
39
44
.
123
137
I+
216
230
161
175
305
311
I+
-181
-267
-198
-208
-337
LE
-3
-6
i
-
-3
-331 -2
H
-5
-7
2
3
i
0
8
4
36
31
-92
2 -116
S = absorbed short wave radiation I = long wave radiation (+ = down, + = up) LE = latent heat flux (positive upward) H = sensible heat flux (positive upward) 0 = oceanic heat exchange with deeper layers of the ocean
Subsequently, more detailed calculations have been carried out in order to examine the role of leads and polynyi.
Using daily data for the Soviet station NP7, which was located in the
Beaufort Sea in 1957-58, Vowinckel and Orvig (1973) calculated monthly averages over ice ( i n i t i a l l y 4m thick) and open water as i l l u s t r a t e d in Table 2.
Their results show that in winter
only 2-3 percent open water is sufficient to balance the calculated sensible heat budget over the entire region.
The observed values at NP-7 indicate that in February 10 percent of the
month contributes 29 percent of the monthly sensible heat flux over ice, and 22 percent over open water, i l l u s t r a t i n g changes.
the importance of individual
synoptic events for the turbulent ex-
This synoptic control operates through variations in cloud cover for an ice surface,
whereas over water there are additional effects due to wind and air mass changes.
For the
total surface energy loss, including long wave radiation, in January-February only 0.1 percent of the surface need be open water in order to equal the loss from the remaining 99.9 percent of the area that is ice covered. Table 2. Calculated energy fluxes over open water and ice in the Beaufort Sea (Win'2) (After Vowinckel and Orvig, 1973) Absorbed Short Wave water lce July
184
111
Net Longwave
Sensible Heat Wa~e
water
Ice
-45
-35
2
-5
Latent Heat Wa~'6~-'Tce 2
-2
Storage change Be)~ Che Surface Wa~e~ ) c e -135
-48
October
5
I
-123
-20
228
-9
57
-2
403
8
February
0
0
-173
-25
764
-16
138
0
1076
11
14l
'N
6000
• • 65/70
5000 ,,~ ~#/
30(30
\\
2000
2000
Total Areo Average
,~°°..
4000
/'/" .....
,%..
70/7S
t
1
Pock Ice; Ice - I000
-2000 - _x,'JO0_ _ _
4~0 Pock Ice,; Open 2OOO
-I000
7000
/
6000 5000 •
i
•
4000
f''J
Open Ocean.
js
~
3OOO
2000 1000
0 - I000
J
Figure 4.
I
I
I
I
I
I
I
I
I
I
I
I
F
M
A
M
J
J
A
S
0
N
D
J
--75"-80ON --70=-75aN ..... 65o_70aN
Evaporation, Norwegian - Barents Sea (cal./cm 2 month). 1965)
(From Vowinckel and Taylor,
Further analysis of the role of open leads and young ice has recently been made by Maykut (1977; 1978).
The calculated
shown in Table 3.
terns for open water, thin ice and thick ice in mid-winter are
The large fluxes for thin ice are maintained by latent heat released during
ice growth, not by ocean transport. ~ y k u t (1977) calculates that one-half of the regionallyaveraged turbulent heat losses in 1963 were due to the a r e a of ice in the 20-80 cm thickness
142 category. Estimated fluxes of sensible heat in the transition seasons in particular are affected by this young ice area.
Table 3.
Calculated energy fluxes over water and ice on 1 February (Wm-2) (from Maykut, 1978)
Net radiation
Open Water -147
.05 m ice -93
.4m ice -45
Sensible heat
-575
-334
-77
16
Latent heat
-147
-45
-6
O
869
472
128
13
Oceanic/conductive heat flux
There are few observations over open leads or young ice.
3m ice -29
Measurements over a freezing lead
near Barrow in March 1974 show a daily net radiation value of -71W m-2 over open water and -78 Wm-2 on the next day over the frozen lead (Holmgren and Weller, 1974). This results from the marked decrease in absorbed short-wave radiation, but the maintenance of large long wave losses due to the relatively high surface temperature of the young ice.
Major practical d i f f i c u l t i e s
hinder such field experiments, especially the rapid closure of leads and the irregular d r i f t of steam fog, forming over the lead, across the instrument site. Almost no work has been performed relating to atmospheric energetics in the SSIZ zone. Drew (1976) illustrates a diagnostic equation,
approach to synoptic-scale
he evaluated components of the vertical
Arctic for January-August, 1973.
Le
processes; using the omega
velocity field over the eastern Canadian
A detailed case-study of a synoptic event was also made
relating to significant ice melt along the eastern coast of Baffin Island.
Le Drew showed the
role of warm air advection from the south and west, augmented by adiabatic compression due to descent in the lee of the coastal mountains. MESOSCALE PHENOMENA Pol ynyi The availability
of satellite
imagery has drawn attention
to the extensive
recurrent
polynyi around Antarctica (Figure 5), especially in the Ross Sea and off Kapp Novegica (Knapp, 1972; Streten, 1973). In the Amundsen Sea (1100 W), for e x i l e , two polynyi typically f~m in early Nova~:er and join with ~
open ocean in late January - early February.
hemisphere they are less prominent features, but are s t i l l
of local
In the no+"chern
importance.
The North
Water of Smith Soured-northern Baffln Bay has been most studied (Dunbar, 1973; Muller et al., 1976), but ~ny other mall polynyii and leads occur in the Canadian Arctic Archlp~lago in spring (Haupt and Kant, 1976) and off the Chukchi Sea coast of Alaska. They are related to
143
90oW
Peninsula
180 °
r
#
f
I'Y~T
.~..,v~acldeto~ / /ce./ ~
Figure 5.
Map showing major polynya locations hatched. (From Streten, 1973.)
"lmL
(closely
shaded).
Ice shelves are cross
coastal orientation in relation to wind and current directions and to the occurrence of local shoals. In the case of the North Water, Muller et al. (1976) show that precipitation on the adjacent land areas may be increased about 33 percent over that otherwise to be expected as the regional background amount. The Fast Ice and Shear Zones From an ice-oriented v i e ~ o i n t , there are striking differences between the landfast ice zone of eastern Baffin Island (Jacobs et al., 1975) and that of the Beaufort-Chukchi Sea off Alaska (Barry, 1977; Stringer, 1978).
In the former the ice is not grounded and extends out
over deep water in some areas such as Home Bay, whereas off northern Alaska i t
is severely
ridged and anchored, particularly over coastal shoals and by the barrier islands (Reimnitz et al., 1978). As a result, much of the seasonal pack ice to seaward may beco~ attached for
144 significant periods in winter.
From a meteorological
standpoint, the boundary-layer windflow
will exhibit greater mechanical turbulence as a result of the surface roughness (Banke et al., 1977), but since the average surface winds off Alaska are typically 5 m s-1 in winter months this factor is probably of l i t t l e
significance.
More important
is the occurrence of 'flaw
leads' in the shear zone. The role of such local heat sources has been discussed above. In late summer and f a l l , the decay of the fast ice allows encroachment of the pack into the coastal zone i f wind conditions are suitable.
On average, the l i m i t of 4/8 ice concentration
retreats 150 km off Point Barrow by 15 September (Barnett, 1976). Light-ice summers are associated with more frequent surface winds with a SE-S'Iy component, while onshore winds predominate in heavy-ice summers (Rogers, 1978). These patterns are associated with an accumulated thawing degree-day (TDD) total
above (below) about 310°C in light-(heavy-)
ice years and in
fact the parameter most highly correlated with ice retreat is this TDD total. bimodal distribution of total
The observed
accumulated TDDs at Barrow is accounted for by the atmosphere-
ocean-ice interaction which favors mild autumns to follow mild summers and vice versa.
A case
study of the severe ice conditions of 1975 along the Beaufort Sea coast has been made by Wendler and Jayaweera (1976).
They draw attention to the role of persistent northwesterly wind
components in keeping the pack ice close to the coast once the fast ice cleared. and their frequency can now be examined via catalogs of synoptic
Such events
pressure patterns such as
those developed for the area by Barry (1977) and Moritz (1978). Arctic Stratus In summer, most of the Arctic Basin surface is melting ice or water with a temperature near O°C. Low cloud averages 40-50 percent over most of the SSIZ and 60-70 percent over the central Polar Ocean.
I t is concentrated in the lowest few hundred meters and is often characterized by
a multilayer structure (Reed and Kunkel, 1960).
This stratus forms as a result of warm air
advection which leads to condensation due to radiative cooling and to diffusive cooling at the surface (Herman and Goody, 1978).
I t has a widely uniform distribution and is highly persist-
ent, indicating that dissipative processes--absorption convective heating, precipitation and synoptic
of solar radiation, evaporation through
scale vertical motion--are all weak, although
the f i r s t of these seems to be the main cause of the layering.
There is insufficient infor-
mation available at present to determine whether there are any major differences in stratus characteristics and their
seasonal regime, between the SSIZ and the central
Polar Ocean.
Vowinckel and Orvig (1970) suggest that the mean water content of the clouds decreases poleward from the arctic coasts. LARGE-SCALE TELECONNECTIONSAND TRENDS There have been various attempts to summarize long-term variations in sea-ice extent in the marginal seas and possible relationship to climatic change. L~b (1977; Lamb and Morth, 1978) reviews some of these studies.
At the present time a major obstacle is the uncertain nature of
145 the basic data.
Satellite
imagery obviously
provides a major opportunity to rectify this
situation, although long-term data sets from single points are very useful i f their r e l i a b i l i t y and representativeness can be established.
Rogers and Van Loon (in press) show that ice in
Davis Strait is most extensive in years following a winter when temperatures in Greenland are below normal (GB) and those in northern Europe are above. This pattern is associated with a strong negative anomaly of sea level pressure north of Iceland implying anomalous northerly flow components over Davis Strait.
Conversely, a reverse pressure anomaly occurs in winters
when north European temperatures are below normal and those in Greenland are above normal (GA). The winter ice extent in the Baltic during GA years is three times greater than in GB years. This anti-phase behavior is also apparent in the results of Haupt and Kant (1976), although they attempt to link ice anomalies in the East Greenland Current to circulation patterns 2-3 years earlier over the Arctic Basin due to the time required for ice d r i f t in the Trans-Polar Drift Stream.
In this context i t is worth noting that Vowinckel (1963) estimates that the heat
gain for the Polar Ocean due to ice and current export could depart 15-20 percent from the mean value in a given year.
The GB/GA pressure anomaly patterns also indicate teleconnections with
the North Pacific atmospheric circulation and eventually this may help to link these results together with the work of Kryndin (1964) on ice conditions off eastern Asia. In view of the work of Rogers and Van Loon (1979), i t is interesting that Keen (1977) finds that the 700 mb trough over eastern Canada has shifted eastward since about 1963, giving rise to more frequent northerly wind components. This matches the trend towards cooler summers and later ice clearance in Baffin Bay. The change in trough location is strongly correlated with an increase in the westerlies in higher latitudes, westerly circulation.
On the regional
perhaps due to a poleward shift of the
scale, Crane (1978A) shows that early ice retreat in
Baffin Bay-Davis Strait occurs in summers with frequent southerly flow components when the upper trough is 40-50 further west. For the fast ice in western Davis Strait, such airflows give warm air advection and high energy fluxes accelerating Jacobs, 1978; Crane, 1978B).
ice melt (Le Drew, 1976; Barry and
In view of the considerable regional differences in ice extent and data uncertainties, i t seems unwise at this time to try and correlate long-term trends with circulation trends within a hemisphere or between hemispheres (Fletcher, 1969). However, this is ultimately an important aspect of the possible global significance of the conditions pheres.
in the SSIZs in the two hemis-
OUTSTANDING PROBLEMS A basic concern in meteorological studies in high latitudes is the r e l i a b i l i t y of the basic data on pressure and other parameters.
Studies by Albright (1978) and Wohl (1978) using AIDJEX
data for 1975 compared with NMC grid-point values illustrates this point.
Wohl found that for
July and August over the Beaufort Sea major synoptic features were missed on 7 days and poorly represented on a further 25 days.
At 80°N, 130°W, the MSL pressure agreed well on only 14
146
days, i t was too high on 14 days and too low on 34 days. This problem has long been recognized but adjustments are seldom attempted (Reed and Kunkel, 1960). Certainly, studies of climatic trends and eigenvector analyses of meteorological
fields and ice concentration (Walsh, 1977,
1978) must take careful account of the uncertainties in both sets of data. series of daily pressure maps is urgently needed.
A good historical
For the future, an improved synoptic c l i -
matology of high-latitude disturbances should be obtained through interpretation of s a t e l l i t e imagery of cloud systems and diagnostic analysis of synoptic systems (Le Drew, 1976). Likewise, a reliable data base of ice limits and concentrations is required.
The a v a i l a b i l i t y of
these sources should enable a much clearer understanding of local, regional, and large-scale ice-climate feedbacks to be obtained (Kellogg, 1975).
To date, the emphasis has primarily been
on atmospheric effects on the ice, rather than the reverse, contrary to what has happened in 3 studies of air-sea interaction. The nature of sea ice-atmosphere interactions can only be determined i f investigations are complemented by selected studies of micrometeorological
the large-scale processes, espe-
cially ice ablation and the energy sinks, and of the characteristics of the planetary boundary layer over the SSIZ. The l a t t e r will involve a combination of a i r c r a f t profiling plus the nowavailable technology for boundary-layer investigations (Lenschow, 1975).
As has been shown by
Vowinckel and Orvig, and by Maykut, information on energy exchange processes can very usefully be incorporated into, or compared with, model calculations.
From their studies, and from other
work (Egorov, et al., 1974), i t is clear that surface albedo and the fraction of open water are probably the two key factors. A major area which has not been touched on this survey is the question of the long-term s t a b i l i t y of the Arctic pack ice. question.
Modelling studies (Parkinson, 1978) promise to address this
Parkinson's results indicate that with a 5°C warming, arctic ice would essentially
be reduced to a seasonal cover,
reforming each winter.
However, i t
must be noted that in
Parkinson's model, the ice l i m i t is forced by the monthly mean air temperature. dependent coupling is necessary to examine this question adequately.
A less inter-
From an empirical
stand
point i t seems reasonable to assume that a better understanding of the processes operating in the SSIZ could contribute greasy to this problem. Finally,
it
is apparent that our basic knowledge of meteorological
SSIZs is very limited.
conditions over the
This is, of course, due to the very unstable nature of the ice surface.
On practical grounds, this question cannot readily be resolved, which implies the need for more indirect observations (remote sensing) coupled with attempts to estimate l i k e l y effects of
3Since this paper was prepared, a study of seasonal ice fluctuations in the Arctic for 19531977 by Walsh and Johnson (1979) indicates that the time scale of sea ice anomalies is l o ~ r than that of atmospheric anomalies of pressure or temperature. Ice v a r i a b i l i t y in the North Atlantic tends to be opposite in sign to that over the remainder of the polar cap.
147 various ice/water
concentrations
on heat, moisture and momentum exchanges through modelling
calculations.
REFERENCES Aagaard, K. (1972), On the d r i f t of the Greenland pack ice. Nat. Res. Council, Reykjavik, 17-22.
In:
Karlsson, T. (ed), Sea Ice,
Ackley, S. F. and Keliher, T. E. (1976), Antarctic sea ice dynamics and its possible climatic effects. AIDJEX Bull., No. 33: 53-76. Albright, M. (1978), Construction of atmospheric surface pressure maps from the AIDJEX data set AIDJEX BULL., No. 39: 111-19. Banke, E., Smith, S.D. and Anderson, R. J. (1977), Drag coefficients at AIDJEX from sonic anemometer measurements. In: Sea ice Processes and Models, (Symposium), I.C.S.I./AIDJEX, September 1977, Vol. I, 142-52 Barnett, D. G., A practical method of long range ice forecasting for the north coast of Alaska. Part I. Tech. Rep. 1, Fleet Wea. Fac., Suitland, Md., 16 pp. Barry, R. G. (1977), Study of climatic effects on fast ice extent and its seasonal decay along the Beaufort-Chukchi coasts. In: Environmental Assessment of the Alaskan Continental Shelf, Vol. XIV, Transport, Environmental Research Laboratories, NOAA, Boulder, 574-743. Barry, R. G. and Jacobs, J.D., with Crane, R. G., Keen, R. A., Moritz, R. E., LeDrew, E. F. and Weaver, R. L. (1978), Energy budget studies in relation to fast-ice breakup processes in Davis Strait: Climatological Overview. Occas. Pap. No. 26, INSTAAR, Univ. of Colorado, Boulder, 284 pp. Bjornsson, H. (1969), Sea ice conditions and the atmospheric circulation north of Iceland. Jokull, 19: 11-17. Bryson, R. A. (1966), Air masses, streamlines and the boreal forest.
Geog. Bull., 8: 228-69.
Budd, W. F. (1975), Antarctic sea-ice variations from satellite remote sensing in relation to climate. J. Glaciol., 15 (73): 417-27. Central Intelligence Agency (1978), Polar Regions Atlas, Nat. Foreign Assessment Cen. C.I.A., Washington, D.C., 66 pp. Crane, R. G. (1978 (A)), Seasonal variations of sea ice extent in the Davis Strait-Labrador Sea area and relationships with synoptic-scale atmospheric circulation. Arctic 31: 434-447. Crane, R. G. (1978 (B)), Synoptic controls on the energy budget regime of an ablating fast ice surface Arch. Met. Geophys. Biokl. A. 28: 53-70. Dunbar, Moira (1967), The monthly and extreme limits of ice in the Bering Sea. In: Oura, H. (ed), Physics of Snow and Ice, Inst. of Low Temp. Sci., Univ. of Hokkaido, Vol. 1, 687-703. Dunbar, Moira, Winter regime of the North Water. Trans. Roy. Soc. Can., Ser. IV, 11: 275-81. Egorov, K. L., Laikhtman, D. L. and Radikevich, V. M. (1974), Ice cover as a link ocean-atmosphere system. Boundary-layer Met., 6: 169-82.
in the
Einarsson, T. (1972), Sea currents, ice d r i f t and ice composition in the East Greenland Current. In: Karlsson, T. (ed.), Sea Ice, Nat. Res. Council, Reykjavik, 23-32.
148 Fletcher, J. O. (1969), Ice extent on the Southern Ocean and i t s relation to world climate. Rand Corp. Memo. RM-5793-NSF, Santa Monica, Calif., 111 pp. Gordon, A. and Taylor, H. (1975), Seasonal change of Antarctic sea ice cover. 345-7.
Science 187:
Haupt, I. and Kant, V. (1976), Satellite ice surveillance studies in the Arctic in relationship to the general circulation. In: Symposium on Meteorlogical Observations from Space: Their Contribution to the First GARP Global Experiment, Proceedings, COSPAR, Internat. Council Sci. Unions, 179-87. Herman, G. F. and Goody, R. (1976) Formation and persistence of summertime arctic clouds. J. Atmos. Sci., 33: 1537-53.
stratus
Herman, G. F. and Johnson, W. T., (1978), The sensitivity of the general circulation to arctic sea ice Boundaries: a numerical experiment. Mon. Wea, Rev., 106: 1649-64. Holmgren, B. and Weller, G. (1974), Local radiation fluxes over open and freezing leads in the polar pack ice. AIDJEX Bull., 17: 149-66. Jacobs, J. D., Barry, R. G., and Weaver, R. L. (1975), Fast ice characteristics, with special reference to the eastern Canadian Arctic. Polar Record 17 (110): 521-36. Keen, R. A. (1977), The response of Baffin Bay ice conditions to changes in atmospheric circulation patterns. In: Muggeridge, D. B. (ed.), Fourth International Conference on Port and Ocean Engineering under Arctic Conditions, Memorial Univ., St. Johns, Newfoundland, Vol. I I , 963-7. Kellogg, W. (1975), Climatic feedback mechanisms involving the polar regions. In: Weller, G., and Bowling, S. A. (eds.), Climate of the Arctic, Univ. of Alaska, Fairbanks, 111-16. Klein, W. H. (1957), Principal tracks and frequencies of cyclones and anticyclones northern hemisphere. U.S. Wea. Bur. Res. Pap. No. 40, Washington, D.C., 60 pp. Knapp, W. W. (1972), Satellite observations of large polynyas in polar waters. T. (ed.), Sea Ice, Nat. Res. Council, Reykjavik, 201-12. Krebs, S. J. and Barry, R. G. (197D), The arctic Eurasia. Geog. Rev. 60: 548-54.
front
In:
in the
Karlsson,
and the tundra-taiga boundary in
Kryndin, A. N. (1964), Seasonal and interannual variations in the ice conditions and the position of the ice boundaries of the Far-Eastern Seas in relation to anomalies of atmospheric circulation. (In Russian). Trudy Gos. Okean. Inst., 71: 5-82. Lamb, H. H. (1977), Climate: Present, Past and Future, Future, Methuen, London, 515-20.
Vol. 2, Climatic
History and the
Lamb, H. H. and Morth, H. J. (1978), Arctic ice, atmospheric circulation and world climate. Geogr. J., 144:1-22. LeDrew, E. F. (1976), Physical mechanisms responsible for the major synoptic systems in the eastern Canadian Arctic in the winter and summer of 1973. Inst. of Arct. Alp. Res., Occas. Pap., No. 22 (NCARCoop. Thesis, No. 38), University of Colorado, Boulder, 205 pp. Lenschow, b. (ed.) (1975), Instruments and techniques for probing the atmospheric boundary layer. Atmos. Technol. No. 7 (NCAR, Boulder, Co.), 91 pp. Maykut, G. A. (1978), Energy exchange over young sea ice in the central Res., 83: 3646-58.
Arctic, J. Geophys.
Maykut, G. A. (1977), Estimates of the regional heat and mass balance of the ice cover in the central Arctic. In: Sea Ice Processes and Models, ICSI/AIDJEX, University of Washington, Seattle: Vol. I, 65-74.
149
Miles, M. K. (1975), North Atlantic circulation and associated temperature gradients. In: Proceedings of the WMO/IAMAP Symposium on Long-Term Climatic Fluctuations, WMO No. 421, Geneva, 189-96. Miles, M. K. (1976), The relation of the poleward flux of sensible heat during the winter half year to some zonal and meridional indices of the circulation. Quart. J. Roy. Met. Soc., 102: 763-8. Moritz, R. E. (1978), Synoptic climatology of the Beaufort Sea coast of Alaska. Unpub. M. A. thesis, Univ. of Colorado, Boulder, 238 pp. Muench, R. D. and Ahlnas, K. (1976), Ice movement and distribution in the Bering Sea from March to June 1974. J. Geophys. Res., 81: 4467-76. Muller, F., Ohmura, A. and Braithwaite, R. (1976), On the climatic influence of North Water. Int. Geogr. Congr. Symp. on the Geography of Polar Countries (Extended Summaries), Hydromet. Publ. House, Leningrad, 55-58. Nusser, R. (1958), Distribution and character of sea ice in the European Arctic. Sea Ice, Publ. 598, Nat. Acad. Sci.--Nat. Res. Council, Washington D.C., 1-10.
In:
Arctic
Parkinson, C. (1978), A numerical simulation of the annual cycle of sea ice in the Arctic and Antarctic. NCARCoop. Thesis, no. 46, Boulder, Co., 191 pp. Reed, R. J. (1960), Principal frontal zones of the northern hemisphere in winter and summer. Bull. Amer. Met. Soc., 41: 591-8. Reed, R. J. and Kunkel, B. A. (1960), The Arctic circulation in summer. J. Met., 17: 489-506. Reimnitz, E., Toimil, L, and Barnes, P. (1978), Arctic continental shelf morphology related to sea ice zonation, Beaufort Sea, Alaska. Marine Geol., 28: 179-210. Rex, D. F. (1950), The effect of Atlantic blocking action upon European climate. 196-211, and 275-301.
Tellus, 2:
Rogers, J. C. (1978), Meteorological factors affecting interannual v a r i a b i l i t y of summertime ice extent in the Beaufort Sea. Mon. Wea. Rev., 106: 890-97. Rogers, J. C. and Van Loon, H. (1979), The seesaw in winter temperatures between Greenland and northern Europe. I I . Sea ice, sea surface temperatures, and winds. Mon. Wea. Rev., 107 (in press). Schell, I. I. (1964), Interrelations of the ice off northern Japan and the weather. SOc. Japan, 42: 174-85.
J. Met.
Schwerdtfeger, W. and Kachelhoffer, S. J. (1973), The frequency of cyclonic vortices over the southern ocean in relation to the extension of the pack ice belt. Antarct. J. United States 8: 234. Streten, N. A. (1973), Satellite observations of the summer decay of the Antarctic sea ice. Arch. Met. Geophys. Biokl., A22: 119-34. Stringer, W. (1978), Nearshore ice conditions by means of satellite and aerial remote sensing. In: Environmental Assessment of the ~askan Continental Shelf. Environmental Research Laboratories, NOAA, Boulder, Co. (in press). Taljaard, J. j . (1972), Synoptic meteorology of the southern hemisphere. In: (ed.), Meteorology of the Southern Hemisphere, Met. Monogr., 13 (35): 25-58.
Newton, C. W.
Van Loon, H. (1972), Temperature in the southern hemisphere. In: Newton, C. W. (ed.), Meteorology of the Southern Hemisphere, Met. Monogr., 13 (35): 25-58.
150 Vinje, T. E. (1977), Sea ice conditions in the European sector of the marginal seas of the Arctic, 1966-1975, Norsk Polarinst. Arbok 1975, 163-74. Vowinckel, E. (1963), Ice transport between Greenland and Spitzbergen, and its Causes. Publ. in Met. NO. 59, Arctic Met. Res. Grp., McGill Univ., Montreal, 23 pp. Vowinckel, E. and Orvig, S. (1966), Energy balance of the Arctic. Arctic Ocean. Arch. Met. Geophys. Biokl., B 14: 303-25.
V. The heat budget over the
Vowinckel, E. and Orvig., S. (1970), The climate of the North Polar Basin. In: Orvig, S. (ed.), Climates of the Polar Regions, World Survey of Climatology. Vol. 14, Elsevier, New York, 129-252. Vowinckel, E. and Orvig, S. (1973), Synoptic energy budgets from the Beaufort Sea. Fluxes over Polar Surfaces, W.M.O. Tech. Note No. 129, W.M.O,, Geneva, 145-66.
In:
Energy
Vowinckel, E. and Taylor, B. (1965), Energy balance of the Arctic. IV Evaporation and sensible heat flux over the Arctic Ocean. Arch. Met. Geophys. Biokl. B 14: 36-52. Walsh, J. E. (1977), Empirical orthogonal functions and the statistical predictability of sea ice extent. In: Sea Ice Processes and Models, (Symposium), I.C.S.I./AIDJEX, September 1977, Vol. I I , 98-107. Walsh, J. E. (1978), Temporal and spatial scales of the Arctic circulation Mon. Wea. Rev., 106: 1532-44. Walsh, J. E. and Johnson, C. M. (1979), An analysis of Arctic sea ice fluctuation, 1953-77. J. Phys. Oceanog. (in press). Wendler, G. and Jayaweera, K.O.L.F (1976), Some remarks on the unusual Beaufort-Sea ice conditions in summer 1975. Univ. of Alaska, Geophys. Inst., Rep. UAG R-246, Fairbanks, 28 pp. Wiese, W. (1924), Polareis and atmospharische Schwankungen. Geograf. Ann., 6: 273-99. Wohi, G. M. (1978), A study of sea ice conditions and synoptic climatology for the Beaufort Sea coast of Alaska. Unpub. M.A. thesis, Univ. of Colorado, Boulder, 166 pp.
and Alpine Research and Department of Geography,
University of Colorado,
INTRODUCTION The extent of the seasonal sea ice zones (SSIZ) in both hemispheres is delineated in Figures 1 and 2 which show the range between the average seasonal maximum and seasonal minimum for ~ i/8 concentration.
A marginal ice zone (MIZ) contiguous with the open ocean represents
one general type of SSIZ, but in Antarctica this is circumglobal extending more or less concentrically around the continent between latitudes 600 and 70°S.
The ice varies greatly in
area between September and March, from about 2.5 x 106 to 20 x 106 km2.
In the northern hemis-
phere, in contrast, there is marked longitudinal asymmetry and the seasonal range is much less, from 7.0 x 106 to 14.1 x 106 km2 (Walsh and Johnson, 1979) due to the land-sea distribution. While the maximum l i m i t of the MIZ extends to south of 50°N in the Sea of Okhotsk and the Labrador Sea, there is open water to the north of 75°N in the Norwegian-Barents Sea. From a meteorological
standpoint,
these MIZs are not
subject to an unlimited
fetch of wind and
currents such as occurs around Antarctica and should, therefore, be regarded as a second type. A third type of SSIZ is represented in the essentially closed Arctic Ocean where the winter extension of the pack ice is constrained by land and shorefast ice, creating shear zones. These are prominent features from the Queen Elizabeth Islands to the Beaufort Sea coast of Alaska. The most extensive SSIZs in the Arctic occur in the Barents-Laptev and Chukchi-Bering "shelf seas". Since the SSIZ is defined by the seasonal range of ice limits, terization is not readily described in a systematic manner. solely determined by meteorological
its meteorological
charac-
Moreover, the ice limits are not
factors, nor does the SSIZ set up a unique climatological
regime. Accordingly, this survey reviews selected aspects of large-scale circulation processes and examples of specific regional
interactions, based on the available l i t e r a t u r e .
Problem
areas are then identified.
AII4OSPHERIC CIRCULATION CHARACTERISTICS Comparison between the summer ice l i m i t in Antarctica and circulation parameters shows that the polar front is located about 45°S and although there is a subsidiary maximum of 1000,500 mb thickness gradient at 70°S there is no strong evidence for a climatic front (Taljaard, 1972, Fig. 8.9).
In addition, in winter the frontal
zones are separated from the pack ice margin,
except perhaps where the ice reaches farthest north to latitude 55°S in the South Atlantic. The situation is well summarized by Van Loon (1972, p. 67) who states:
"In the transition
seasons when the mean position of the circumpolar trough is nearest Antarctica, the border of
135
120°
90°E
60 °
150°
180°
150°
120°
Figure I.
90°W
60 °
Northern Hemisphere SSIZ (after CIA, 1978)
the ice is near i t s extreme poleward and equatorward positions.
In the months when the trough
on the average is farthest north, the ice border has reached no such extreme position."
The
frontal maxima, especially in the South Atlantic and South Indian Oceans are instead closely related to sea surface temperature gradients associated with the Subtropical
and Antarctic
Convergences. There is, nevertheless, a close seasonal relationship between the ice margin and the latitudinal
band of maximum cyclone frequency in the transition
Schwerdtfeger and Kachelhoffer (1973).
seasons according to
This is examined further below.
In the northern hemisphere the three areas of extensive winter ice; the Bering-0kh~tsk Sea,
the eastern Canadian Arctic and Subarctic, and the Barents Sea, are all located close to mean January and April 700 mb pressure troughs.
The mean contours indicate advection of cold north-
westerly air streams on the western side of these troughs.
In contrast, the longitudes
of
136
30 °
0o
30°
I EXTENT OF SEA ICE ~> 1/8 CONCENTRATION
60° 60°
~OUTH
90°W
J,POLE
90OE
120° ~'-/0
~
~
/M~oluteMin.
120°
~eters~ 150°
180°
Figure 2. Scandinavia,
Alaska,
150°
Northern Hemisphere SSIZ (after CIA, 1978)
and to a lesser extent Greenland, are sectors where, particularly
spring, there are maxima of blocking ridges (Rex, 1950).
In winter the mean polar frontal
zones are well south of the ice margins but there is a secondary ' a r c t i c ' eastern North Atlantic.
in
front in the north-
A major depression track from Newfoundland to Iceland parallels the
ice margin (Klein, 1957), although i t is displaced southward 80-90 latitude.
In summer, the
arctic front l i e s over the forest-tundra ecotone on land (Reed, 1960; Bryson, 1966; Krebs and Barry, 1970), but there is a secondary cyclone track along the Arctic coasts of Siberia and Alaska both in summer and in fall
(Klein, 1957).
137 ATMOSPHERIC CIRCULATION/ICE FEEDBACKS This topic
has been approached by descriptive synoptic case studies and by simulation
experiments with circulation models.
Potentially,
budget calculations on a synoptic basis.
it
also requires examination via energy
For Antarctica, the dramatic seasonal expansion and
contraction of the sea ice has been explained by Gordon and Taylor (1975) in terms of (1) the Ekman divergence due to the curl of the wind stress, and (2) the surface heat balance.
The
f i r s t factor is associated with cyclonic activity, while the second is related to open water areas in the case of the summertime decay of the pack. They suggest that with a more northern location of cyclonic activity there would be more ice cover and, therefore, reduced upwelling, in turn limiting summer melt and hence lessening the seasonal fluctuation. The extent to which storm activity may cause a positive feedback between atmosphere and sea ice has been examined by Ackley and Keliher (1976).
A rapid decrease in sea ice in the
Bellingshausen Sea in 1973 is thought to have caused a relative gain in atmospheric heat, thereby augmenting cyclone activity which in turn helped to maintain less ice cover.
Figure 3
illustrates the anomaly of atmospheric heat loss in 1973, which may have been up to an order of magnitude greater
than the average total
energy of a midlatitude cyclone (2.1 x 1016Kj).
Ackley and Keliher propose that usually the ice concentration is sufficient for storm activity to cause its convergence, reducing the sensible heat flux and thereby increasing the net atmospheric heat loss.
However, poleward flow of warmer air, with meridional blocking patterns, may
decrease the ice extent and its concentration.
Under such conditions, enhanced storm activity
could cause divergence of the pack. From averaged data, Budd (1975) indicates that a I°C increase in mean annual temperature corresponds to a 2.50 latitude change at latitude 60°S, suggesting a stable feedback relationship. 1 There is also a 70 day reduction in the duration of ice cover in Scotia Bay for an average 1°C warming. Budd suggests that more extensive ice may increase the meridional temperature and pressure gradients and, therefore, the zonal (westerly) circulation.
However, Miles (1975) demonstrates
for the North Atlantic that such a relationship does not hold on the 5-30 year time scale. Indeed, there may have been a slight increase in poleward sensible heat flux associated with the post-1930 decrease in zonal circulation (Miles, 1976). In the northern hemisphere, where the overall pattern of ice extent is strongly influenced by the interactive oceanic and atmospheric circulations, most investigations have been regional in character.
The causes of anomalies in ice extent in the North Atlantic sector 2 have been
IA 10 latitude change in the ice l i m i t represents a change of about 15 percent in hemisphere sea ice cover (Streten, 1973).
138
0 ~
,,
,
,I
,
'
i
I
,
l
,
r
l
I.
•
.
.
.
.
J
r U
50
01
i
i
l
#s,io~,,,
oI
'~°~S
l,
+
I
i
l
+..tot.+
-'+
I
',:p, i+
+
•
,
1~t
,op p..m
+ Figure 3.
~
,
1
Ice pack characteristics, atmospheric heat loss, and n~mber of low days per week for Sector I (Amundsen-Bellinghausen) for 1973. (from Ackley and Keliher, 1976).
examined on synoptic to monthly time scales by many investigators (see Nusser, 1958; Bjornsson, 1969; Haupt and Kant, 1976; Vinje, 1977).
An analysis of anomalies off East Greenland by
Aagaard (1972) shows that when the late-winter/spring pressure pattern resembles the mean map, with a trough extending northeastward from the Icelandic Low, this generates cyclonic curl of the wind stress and northward retreat of the ice.
In contrast, in years with high pressure
over Greenland, there is southward current and ice transport due to the anticyclonic curl. According to Vowinckel (1963), 2/3 of the total ice export is due to the current and only I/3 to wind-induced export. He also shows from correlation analysis of ice extent between April and August, and August with the following April, that freeze and melt processes tend to dampen variations caused by ice import.
Since the influence of wind velocity may strongly influence
the ice margin on the time scale of a week (Einarsson, 1972) i t is important to ask whether this is long enough for major feedback effects on the atmosphere. From Ackley and Keliher's work, discussed above, i t would appear that a 10-day period is certainly sufficient for such effects to operate on a regional scale. 2Processes operating ni the Baltic Sea and Hudson Bay are rather special and are not discussed here. Schell (1964) has performed comparable investigations in the Sea of Okhotsk.
139 In the Bering Sea where the seasonal ice maximum approximates the edge of the continental shelf, the limiting control on ice extent is probably heat transport by the Pacific Current according to Dunbar (1976).
However, the role of northerly winds in spring 1976 has been
demonstrated by Muench and Ahlnas (1976).
They estimate that the mean observed southward
motion of 1.8 m s-1 would require a minimum heat loss of 42 Wm-2 for ice formation.
I f most
of the ice forms in divergent areas of open water and thin ice, this value would increase by an order of magnitude. The effects of sea ice anomalies on the atmospheric circulation has been examined empirically by Wiese (1924) and through a GCM experiment by Herman and Johnson (1978). Wiese showed that, in the North Atlantic, cyclone tracks are further south in years with heavy ice than in years with light ice.
This result has been confirmed by Herman and Johnson. Using the GISS
GCM, they compare a mean of two mid-winter
simulations with 'maximum' ice in the northern
oceans (corresponding to observed conditions) with the mean of six simulations with minimum mid-winter ice extent. circulation.
They demonstrate both local and hemispheric effects on the atmospheric
With maximum sea ice there is an increase of sea-level pressure over the ice and
a southward shift of cyclones in the North Atlantic, giving increased precipitation over northern Europe. coupled with latitudes.
On the hemispheric scale, deeper Icelandic and Gulf of Alaska lows at 700 mb are stronger
subtropical
anticyclones
and enhanced poleward energy flux
in mid-
Herman and Johnson note, however, that the model omits feedback processes, includ-
ing changes in sea surface temperatures. ENERGY BUDGETS The large-scale energy budget regimes of the Polar Ocean and adjacent seas are well known in broad terms from observational
and analytical studies.
In particular, Vowinckel and Orvig
(1966, 1970) and Vowinckel and Taylor (1965) have mapped calculated values for the whole area and distinguished several distinctive seasonal energy regimes. They identify the pack ice of the central tinental
Polar Ocean as a transitional
type, resembling oceanic areas in summer and con-
areas in winter and the transition seasons.
In the context of the SSIZ, the map
delimiting regions investigated shows that only the Kara-Laptev Sea area is essentially located within the SSIZ. Their analysis of the Norwegian-Barents Sea includes all the area north of 65°N, for example. Table 1 summarizes their results for the central Polar ocean and the KaraLaptev seas for annual totals and the extreme months.
Interestingly, the results for the
latter are consistently much closer to the central Polar Ocean than to their calculated values for the Norwegian-Barents Sea. Their calculations indicate that the evaporative heat-loss from open pack ice is very similar to that from an open ocean, except in summer months at 650/700 N and 700/ 750 N when there is evaporative heat loss over open water but a small heat gain to open pack ice (Figure 4).
140 Table 1.
Energy fluxes at the surface in the Arctic (Wm'2)(after ANNUAL Central Polar Ocean
JANUARY Central Polar Ocean
KaraLaptev Sea
.
JULY Central Polar Ocean
KaraLaptev Sea .
Vowinckel and Orvig, 1966)
.
KaraLaptev Sea
S
39
44
.
123
137
I+
216
230
161
175
305
311
I+
-181
-267
-198
-208
-337
LE
-3
-6
i
-
-3
-331 -2
H
-5
-7
2
3
i
0
8
4
36
31
-92
2 -116
S = absorbed short wave radiation I = long wave radiation (+ = down, + = up) LE = latent heat flux (positive upward) H = sensible heat flux (positive upward) 0 = oceanic heat exchange with deeper layers of the ocean
Subsequently, more detailed calculations have been carried out in order to examine the role of leads and polynyi.
Using daily data for the Soviet station NP7, which was located in the
Beaufort Sea in 1957-58, Vowinckel and Orvig (1973) calculated monthly averages over ice ( i n i t i a l l y 4m thick) and open water as i l l u s t r a t e d in Table 2.
Their results show that in winter
only 2-3 percent open water is sufficient to balance the calculated sensible heat budget over the entire region.
The observed values at NP-7 indicate that in February 10 percent of the
month contributes 29 percent of the monthly sensible heat flux over ice, and 22 percent over open water, i l l u s t r a t i n g changes.
the importance of individual
synoptic events for the turbulent ex-
This synoptic control operates through variations in cloud cover for an ice surface,
whereas over water there are additional effects due to wind and air mass changes.
For the
total surface energy loss, including long wave radiation, in January-February only 0.1 percent of the surface need be open water in order to equal the loss from the remaining 99.9 percent of the area that is ice covered. Table 2. Calculated energy fluxes over open water and ice in the Beaufort Sea (Win'2) (After Vowinckel and Orvig, 1973) Absorbed Short Wave water lce July
184
111
Net Longwave
Sensible Heat Wa~e
water
Ice
-45
-35
2
-5
Latent Heat Wa~'6~-'Tce 2
-2
Storage change Be)~ Che Surface Wa~e~ ) c e -135
-48
October
5
I
-123
-20
228
-9
57
-2
403
8
February
0
0
-173
-25
764
-16
138
0
1076
11
14l
'N
6000
• • 65/70
5000 ,,~ ~#/
30(30
\\
2000
2000
Total Areo Average
,~°°..
4000
/'/" .....
,%..
70/7S
t
1
Pock Ice; Ice - I000
-2000 - _x,'JO0_ _ _
4~0 Pock Ice,; Open 2OOO
-I000
7000
/
6000 5000 •
i
•
4000
f''J
Open Ocean.
js
~
3OOO
2000 1000
0 - I000
J
Figure 4.
I
I
I
I
I
I
I
I
I
I
I
I
F
M
A
M
J
J
A
S
0
N
D
J
--75"-80ON --70=-75aN ..... 65o_70aN
Evaporation, Norwegian - Barents Sea (cal./cm 2 month). 1965)
(From Vowinckel and Taylor,
Further analysis of the role of open leads and young ice has recently been made by Maykut (1977; 1978).
The calculated
shown in Table 3.
terns for open water, thin ice and thick ice in mid-winter are
The large fluxes for thin ice are maintained by latent heat released during
ice growth, not by ocean transport. ~ y k u t (1977) calculates that one-half of the regionallyaveraged turbulent heat losses in 1963 were due to the a r e a of ice in the 20-80 cm thickness
142 category. Estimated fluxes of sensible heat in the transition seasons in particular are affected by this young ice area.
Table 3.
Calculated energy fluxes over water and ice on 1 February (Wm-2) (from Maykut, 1978)
Net radiation
Open Water -147
.05 m ice -93
.4m ice -45
Sensible heat
-575
-334
-77
16
Latent heat
-147
-45
-6
O
869
472
128
13
Oceanic/conductive heat flux
There are few observations over open leads or young ice.
3m ice -29
Measurements over a freezing lead
near Barrow in March 1974 show a daily net radiation value of -71W m-2 over open water and -78 Wm-2 on the next day over the frozen lead (Holmgren and Weller, 1974). This results from the marked decrease in absorbed short-wave radiation, but the maintenance of large long wave losses due to the relatively high surface temperature of the young ice.
Major practical d i f f i c u l t i e s
hinder such field experiments, especially the rapid closure of leads and the irregular d r i f t of steam fog, forming over the lead, across the instrument site. Almost no work has been performed relating to atmospheric energetics in the SSIZ zone. Drew (1976) illustrates a diagnostic equation,
approach to synoptic-scale
he evaluated components of the vertical
Arctic for January-August, 1973.
Le
processes; using the omega
velocity field over the eastern Canadian
A detailed case-study of a synoptic event was also made
relating to significant ice melt along the eastern coast of Baffin Island.
Le Drew showed the
role of warm air advection from the south and west, augmented by adiabatic compression due to descent in the lee of the coastal mountains. MESOSCALE PHENOMENA Pol ynyi The availability
of satellite
imagery has drawn attention
to the extensive
recurrent
polynyi around Antarctica (Figure 5), especially in the Ross Sea and off Kapp Novegica (Knapp, 1972; Streten, 1973). In the Amundsen Sea (1100 W), for e x i l e , two polynyi typically f~m in early Nova~:er and join with ~
open ocean in late January - early February.
hemisphere they are less prominent features, but are s t i l l
of local
In the no+"chern
importance.
The North
Water of Smith Soured-northern Baffln Bay has been most studied (Dunbar, 1973; Muller et al., 1976), but ~ny other mall polynyii and leads occur in the Canadian Arctic Archlp~lago in spring (Haupt and Kant, 1976) and off the Chukchi Sea coast of Alaska. They are related to
143
90oW
Peninsula
180 °
r
#
f
I'Y~T
.~..,v~acldeto~ / /ce./ ~
Figure 5.
Map showing major polynya locations hatched. (From Streten, 1973.)
"lmL
(closely
shaded).
Ice shelves are cross
coastal orientation in relation to wind and current directions and to the occurrence of local shoals. In the case of the North Water, Muller et al. (1976) show that precipitation on the adjacent land areas may be increased about 33 percent over that otherwise to be expected as the regional background amount. The Fast Ice and Shear Zones From an ice-oriented v i e ~ o i n t , there are striking differences between the landfast ice zone of eastern Baffin Island (Jacobs et al., 1975) and that of the Beaufort-Chukchi Sea off Alaska (Barry, 1977; Stringer, 1978).
In the former the ice is not grounded and extends out
over deep water in some areas such as Home Bay, whereas off northern Alaska i t
is severely
ridged and anchored, particularly over coastal shoals and by the barrier islands (Reimnitz et al., 1978). As a result, much of the seasonal pack ice to seaward may beco~ attached for
144 significant periods in winter.
From a meteorological
standpoint, the boundary-layer windflow
will exhibit greater mechanical turbulence as a result of the surface roughness (Banke et al., 1977), but since the average surface winds off Alaska are typically 5 m s-1 in winter months this factor is probably of l i t t l e
significance.
More important
is the occurrence of 'flaw
leads' in the shear zone. The role of such local heat sources has been discussed above. In late summer and f a l l , the decay of the fast ice allows encroachment of the pack into the coastal zone i f wind conditions are suitable.
On average, the l i m i t of 4/8 ice concentration
retreats 150 km off Point Barrow by 15 September (Barnett, 1976). Light-ice summers are associated with more frequent surface winds with a SE-S'Iy component, while onshore winds predominate in heavy-ice summers (Rogers, 1978). These patterns are associated with an accumulated thawing degree-day (TDD) total
above (below) about 310°C in light-(heavy-)
ice years and in
fact the parameter most highly correlated with ice retreat is this TDD total. bimodal distribution of total
The observed
accumulated TDDs at Barrow is accounted for by the atmosphere-
ocean-ice interaction which favors mild autumns to follow mild summers and vice versa.
A case
study of the severe ice conditions of 1975 along the Beaufort Sea coast has been made by Wendler and Jayaweera (1976).
They draw attention to the role of persistent northwesterly wind
components in keeping the pack ice close to the coast once the fast ice cleared. and their frequency can now be examined via catalogs of synoptic
Such events
pressure patterns such as
those developed for the area by Barry (1977) and Moritz (1978). Arctic Stratus In summer, most of the Arctic Basin surface is melting ice or water with a temperature near O°C. Low cloud averages 40-50 percent over most of the SSIZ and 60-70 percent over the central Polar Ocean.
I t is concentrated in the lowest few hundred meters and is often characterized by
a multilayer structure (Reed and Kunkel, 1960).
This stratus forms as a result of warm air
advection which leads to condensation due to radiative cooling and to diffusive cooling at the surface (Herman and Goody, 1978).
I t has a widely uniform distribution and is highly persist-
ent, indicating that dissipative processes--absorption convective heating, precipitation and synoptic
of solar radiation, evaporation through
scale vertical motion--are all weak, although
the f i r s t of these seems to be the main cause of the layering.
There is insufficient infor-
mation available at present to determine whether there are any major differences in stratus characteristics and their
seasonal regime, between the SSIZ and the central
Polar Ocean.
Vowinckel and Orvig (1970) suggest that the mean water content of the clouds decreases poleward from the arctic coasts. LARGE-SCALE TELECONNECTIONSAND TRENDS There have been various attempts to summarize long-term variations in sea-ice extent in the marginal seas and possible relationship to climatic change. L~b (1977; Lamb and Morth, 1978) reviews some of these studies.
At the present time a major obstacle is the uncertain nature of
145 the basic data.
Satellite
imagery obviously
provides a major opportunity to rectify this
situation, although long-term data sets from single points are very useful i f their r e l i a b i l i t y and representativeness can be established.
Rogers and Van Loon (in press) show that ice in
Davis Strait is most extensive in years following a winter when temperatures in Greenland are below normal (GB) and those in northern Europe are above. This pattern is associated with a strong negative anomaly of sea level pressure north of Iceland implying anomalous northerly flow components over Davis Strait.
Conversely, a reverse pressure anomaly occurs in winters
when north European temperatures are below normal and those in Greenland are above normal (GA). The winter ice extent in the Baltic during GA years is three times greater than in GB years. This anti-phase behavior is also apparent in the results of Haupt and Kant (1976), although they attempt to link ice anomalies in the East Greenland Current to circulation patterns 2-3 years earlier over the Arctic Basin due to the time required for ice d r i f t in the Trans-Polar Drift Stream.
In this context i t is worth noting that Vowinckel (1963) estimates that the heat
gain for the Polar Ocean due to ice and current export could depart 15-20 percent from the mean value in a given year.
The GB/GA pressure anomaly patterns also indicate teleconnections with
the North Pacific atmospheric circulation and eventually this may help to link these results together with the work of Kryndin (1964) on ice conditions off eastern Asia. In view of the work of Rogers and Van Loon (1979), i t is interesting that Keen (1977) finds that the 700 mb trough over eastern Canada has shifted eastward since about 1963, giving rise to more frequent northerly wind components. This matches the trend towards cooler summers and later ice clearance in Baffin Bay. The change in trough location is strongly correlated with an increase in the westerlies in higher latitudes, westerly circulation.
On the regional
perhaps due to a poleward shift of the
scale, Crane (1978A) shows that early ice retreat in
Baffin Bay-Davis Strait occurs in summers with frequent southerly flow components when the upper trough is 40-50 further west. For the fast ice in western Davis Strait, such airflows give warm air advection and high energy fluxes accelerating Jacobs, 1978; Crane, 1978B).
ice melt (Le Drew, 1976; Barry and
In view of the considerable regional differences in ice extent and data uncertainties, i t seems unwise at this time to try and correlate long-term trends with circulation trends within a hemisphere or between hemispheres (Fletcher, 1969). However, this is ultimately an important aspect of the possible global significance of the conditions pheres.
in the SSIZs in the two hemis-
OUTSTANDING PROBLEMS A basic concern in meteorological studies in high latitudes is the r e l i a b i l i t y of the basic data on pressure and other parameters.
Studies by Albright (1978) and Wohl (1978) using AIDJEX
data for 1975 compared with NMC grid-point values illustrates this point.
Wohl found that for
July and August over the Beaufort Sea major synoptic features were missed on 7 days and poorly represented on a further 25 days.
At 80°N, 130°W, the MSL pressure agreed well on only 14
146
days, i t was too high on 14 days and too low on 34 days. This problem has long been recognized but adjustments are seldom attempted (Reed and Kunkel, 1960). Certainly, studies of climatic trends and eigenvector analyses of meteorological
fields and ice concentration (Walsh, 1977,
1978) must take careful account of the uncertainties in both sets of data. series of daily pressure maps is urgently needed.
A good historical
For the future, an improved synoptic c l i -
matology of high-latitude disturbances should be obtained through interpretation of s a t e l l i t e imagery of cloud systems and diagnostic analysis of synoptic systems (Le Drew, 1976). Likewise, a reliable data base of ice limits and concentrations is required.
The a v a i l a b i l i t y of
these sources should enable a much clearer understanding of local, regional, and large-scale ice-climate feedbacks to be obtained (Kellogg, 1975).
To date, the emphasis has primarily been
on atmospheric effects on the ice, rather than the reverse, contrary to what has happened in 3 studies of air-sea interaction. The nature of sea ice-atmosphere interactions can only be determined i f investigations are complemented by selected studies of micrometeorological
the large-scale processes, espe-
cially ice ablation and the energy sinks, and of the characteristics of the planetary boundary layer over the SSIZ. The l a t t e r will involve a combination of a i r c r a f t profiling plus the nowavailable technology for boundary-layer investigations (Lenschow, 1975).
As has been shown by
Vowinckel and Orvig, and by Maykut, information on energy exchange processes can very usefully be incorporated into, or compared with, model calculations.
From their studies, and from other
work (Egorov, et al., 1974), i t is clear that surface albedo and the fraction of open water are probably the two key factors. A major area which has not been touched on this survey is the question of the long-term s t a b i l i t y of the Arctic pack ice. question.
Modelling studies (Parkinson, 1978) promise to address this
Parkinson's results indicate that with a 5°C warming, arctic ice would essentially
be reduced to a seasonal cover,
reforming each winter.
However, i t
must be noted that in
Parkinson's model, the ice l i m i t is forced by the monthly mean air temperature. dependent coupling is necessary to examine this question adequately.
A less inter-
From an empirical
stand
point i t seems reasonable to assume that a better understanding of the processes operating in the SSIZ could contribute greasy to this problem. Finally,
it
is apparent that our basic knowledge of meteorological
SSIZs is very limited.
conditions over the
This is, of course, due to the very unstable nature of the ice surface.
On practical grounds, this question cannot readily be resolved, which implies the need for more indirect observations (remote sensing) coupled with attempts to estimate l i k e l y effects of
3Since this paper was prepared, a study of seasonal ice fluctuations in the Arctic for 19531977 by Walsh and Johnson (1979) indicates that the time scale of sea ice anomalies is l o ~ r than that of atmospheric anomalies of pressure or temperature. Ice v a r i a b i l i t y in the North Atlantic tends to be opposite in sign to that over the remainder of the polar cap.
147 various ice/water
concentrations
on heat, moisture and momentum exchanges through modelling
calculations.
REFERENCES Aagaard, K. (1972), On the d r i f t of the Greenland pack ice. Nat. Res. Council, Reykjavik, 17-22.
In:
Karlsson, T. (ed), Sea Ice,
Ackley, S. F. and Keliher, T. E. (1976), Antarctic sea ice dynamics and its possible climatic effects. AIDJEX Bull., No. 33: 53-76. Albright, M. (1978), Construction of atmospheric surface pressure maps from the AIDJEX data set AIDJEX BULL., No. 39: 111-19. Banke, E., Smith, S.D. and Anderson, R. J. (1977), Drag coefficients at AIDJEX from sonic anemometer measurements. In: Sea ice Processes and Models, (Symposium), I.C.S.I./AIDJEX, September 1977, Vol. I, 142-52 Barnett, D. G., A practical method of long range ice forecasting for the north coast of Alaska. Part I. Tech. Rep. 1, Fleet Wea. Fac., Suitland, Md., 16 pp. Barry, R. G. (1977), Study of climatic effects on fast ice extent and its seasonal decay along the Beaufort-Chukchi coasts. In: Environmental Assessment of the Alaskan Continental Shelf, Vol. XIV, Transport, Environmental Research Laboratories, NOAA, Boulder, 574-743. Barry, R. G. and Jacobs, J.D., with Crane, R. G., Keen, R. A., Moritz, R. E., LeDrew, E. F. and Weaver, R. L. (1978), Energy budget studies in relation to fast-ice breakup processes in Davis Strait: Climatological Overview. Occas. Pap. No. 26, INSTAAR, Univ. of Colorado, Boulder, 284 pp. Bjornsson, H. (1969), Sea ice conditions and the atmospheric circulation north of Iceland. Jokull, 19: 11-17. Bryson, R. A. (1966), Air masses, streamlines and the boreal forest.
Geog. Bull., 8: 228-69.
Budd, W. F. (1975), Antarctic sea-ice variations from satellite remote sensing in relation to climate. J. Glaciol., 15 (73): 417-27. Central Intelligence Agency (1978), Polar Regions Atlas, Nat. Foreign Assessment Cen. C.I.A., Washington, D.C., 66 pp. Crane, R. G. (1978 (A)), Seasonal variations of sea ice extent in the Davis Strait-Labrador Sea area and relationships with synoptic-scale atmospheric circulation. Arctic 31: 434-447. Crane, R. G. (1978 (B)), Synoptic controls on the energy budget regime of an ablating fast ice surface Arch. Met. Geophys. Biokl. A. 28: 53-70. Dunbar, Moira (1967), The monthly and extreme limits of ice in the Bering Sea. In: Oura, H. (ed), Physics of Snow and Ice, Inst. of Low Temp. Sci., Univ. of Hokkaido, Vol. 1, 687-703. Dunbar, Moira, Winter regime of the North Water. Trans. Roy. Soc. Can., Ser. IV, 11: 275-81. Egorov, K. L., Laikhtman, D. L. and Radikevich, V. M. (1974), Ice cover as a link ocean-atmosphere system. Boundary-layer Met., 6: 169-82.
in the
Einarsson, T. (1972), Sea currents, ice d r i f t and ice composition in the East Greenland Current. In: Karlsson, T. (ed.), Sea Ice, Nat. Res. Council, Reykjavik, 23-32.
148 Fletcher, J. O. (1969), Ice extent on the Southern Ocean and i t s relation to world climate. Rand Corp. Memo. RM-5793-NSF, Santa Monica, Calif., 111 pp. Gordon, A. and Taylor, H. (1975), Seasonal change of Antarctic sea ice cover. 345-7.
Science 187:
Haupt, I. and Kant, V. (1976), Satellite ice surveillance studies in the Arctic in relationship to the general circulation. In: Symposium on Meteorlogical Observations from Space: Their Contribution to the First GARP Global Experiment, Proceedings, COSPAR, Internat. Council Sci. Unions, 179-87. Herman, G. F. and Goody, R. (1976) Formation and persistence of summertime arctic clouds. J. Atmos. Sci., 33: 1537-53.
stratus
Herman, G. F. and Johnson, W. T., (1978), The sensitivity of the general circulation to arctic sea ice Boundaries: a numerical experiment. Mon. Wea, Rev., 106: 1649-64. Holmgren, B. and Weller, G. (1974), Local radiation fluxes over open and freezing leads in the polar pack ice. AIDJEX Bull., 17: 149-66. Jacobs, J. D., Barry, R. G., and Weaver, R. L. (1975), Fast ice characteristics, with special reference to the eastern Canadian Arctic. Polar Record 17 (110): 521-36. Keen, R. A. (1977), The response of Baffin Bay ice conditions to changes in atmospheric circulation patterns. In: Muggeridge, D. B. (ed.), Fourth International Conference on Port and Ocean Engineering under Arctic Conditions, Memorial Univ., St. Johns, Newfoundland, Vol. I I , 963-7. Kellogg, W. (1975), Climatic feedback mechanisms involving the polar regions. In: Weller, G., and Bowling, S. A. (eds.), Climate of the Arctic, Univ. of Alaska, Fairbanks, 111-16. Klein, W. H. (1957), Principal tracks and frequencies of cyclones and anticyclones northern hemisphere. U.S. Wea. Bur. Res. Pap. No. 40, Washington, D.C., 60 pp. Knapp, W. W. (1972), Satellite observations of large polynyas in polar waters. T. (ed.), Sea Ice, Nat. Res. Council, Reykjavik, 201-12. Krebs, S. J. and Barry, R. G. (197D), The arctic Eurasia. Geog. Rev. 60: 548-54.
front
In:
in the
Karlsson,
and the tundra-taiga boundary in
Kryndin, A. N. (1964), Seasonal and interannual variations in the ice conditions and the position of the ice boundaries of the Far-Eastern Seas in relation to anomalies of atmospheric circulation. (In Russian). Trudy Gos. Okean. Inst., 71: 5-82. Lamb, H. H. (1977), Climate: Present, Past and Future, Future, Methuen, London, 515-20.
Vol. 2, Climatic
History and the
Lamb, H. H. and Morth, H. J. (1978), Arctic ice, atmospheric circulation and world climate. Geogr. J., 144:1-22. LeDrew, E. F. (1976), Physical mechanisms responsible for the major synoptic systems in the eastern Canadian Arctic in the winter and summer of 1973. Inst. of Arct. Alp. Res., Occas. Pap., No. 22 (NCARCoop. Thesis, No. 38), University of Colorado, Boulder, 205 pp. Lenschow, b. (ed.) (1975), Instruments and techniques for probing the atmospheric boundary layer. Atmos. Technol. No. 7 (NCAR, Boulder, Co.), 91 pp. Maykut, G. A. (1978), Energy exchange over young sea ice in the central Res., 83: 3646-58.
Arctic, J. Geophys.
Maykut, G. A. (1977), Estimates of the regional heat and mass balance of the ice cover in the central Arctic. In: Sea Ice Processes and Models, ICSI/AIDJEX, University of Washington, Seattle: Vol. I, 65-74.
149
Miles, M. K. (1975), North Atlantic circulation and associated temperature gradients. In: Proceedings of the WMO/IAMAP Symposium on Long-Term Climatic Fluctuations, WMO No. 421, Geneva, 189-96. Miles, M. K. (1976), The relation of the poleward flux of sensible heat during the winter half year to some zonal and meridional indices of the circulation. Quart. J. Roy. Met. Soc., 102: 763-8. Moritz, R. E. (1978), Synoptic climatology of the Beaufort Sea coast of Alaska. Unpub. M. A. thesis, Univ. of Colorado, Boulder, 238 pp. Muench, R. D. and Ahlnas, K. (1976), Ice movement and distribution in the Bering Sea from March to June 1974. J. Geophys. Res., 81: 4467-76. Muller, F., Ohmura, A. and Braithwaite, R. (1976), On the climatic influence of North Water. Int. Geogr. Congr. Symp. on the Geography of Polar Countries (Extended Summaries), Hydromet. Publ. House, Leningrad, 55-58. Nusser, R. (1958), Distribution and character of sea ice in the European Arctic. Sea Ice, Publ. 598, Nat. Acad. Sci.--Nat. Res. Council, Washington D.C., 1-10.
In:
Arctic
Parkinson, C. (1978), A numerical simulation of the annual cycle of sea ice in the Arctic and Antarctic. NCARCoop. Thesis, no. 46, Boulder, Co., 191 pp. Reed, R. J. (1960), Principal frontal zones of the northern hemisphere in winter and summer. Bull. Amer. Met. Soc., 41: 591-8. Reed, R. J. and Kunkel, B. A. (1960), The Arctic circulation in summer. J. Met., 17: 489-506. Reimnitz, E., Toimil, L, and Barnes, P. (1978), Arctic continental shelf morphology related to sea ice zonation, Beaufort Sea, Alaska. Marine Geol., 28: 179-210. Rex, D. F. (1950), The effect of Atlantic blocking action upon European climate. 196-211, and 275-301.
Tellus, 2:
Rogers, J. C. (1978), Meteorological factors affecting interannual v a r i a b i l i t y of summertime ice extent in the Beaufort Sea. Mon. Wea. Rev., 106: 890-97. Rogers, J. C. and Van Loon, H. (1979), The seesaw in winter temperatures between Greenland and northern Europe. I I . Sea ice, sea surface temperatures, and winds. Mon. Wea. Rev., 107 (in press). Schell, I. I. (1964), Interrelations of the ice off northern Japan and the weather. SOc. Japan, 42: 174-85.
J. Met.
Schwerdtfeger, W. and Kachelhoffer, S. J. (1973), The frequency of cyclonic vortices over the southern ocean in relation to the extension of the pack ice belt. Antarct. J. United States 8: 234. Streten, N. A. (1973), Satellite observations of the summer decay of the Antarctic sea ice. Arch. Met. Geophys. Biokl., A22: 119-34. Stringer, W. (1978), Nearshore ice conditions by means of satellite and aerial remote sensing. In: Environmental Assessment of the ~askan Continental Shelf. Environmental Research Laboratories, NOAA, Boulder, Co. (in press). Taljaard, J. j . (1972), Synoptic meteorology of the southern hemisphere. In: (ed.), Meteorology of the Southern Hemisphere, Met. Monogr., 13 (35): 25-58.
Newton, C. W.
Van Loon, H. (1972), Temperature in the southern hemisphere. In: Newton, C. W. (ed.), Meteorology of the Southern Hemisphere, Met. Monogr., 13 (35): 25-58.
150 Vinje, T. E. (1977), Sea ice conditions in the European sector of the marginal seas of the Arctic, 1966-1975, Norsk Polarinst. Arbok 1975, 163-74. Vowinckel, E. (1963), Ice transport between Greenland and Spitzbergen, and its Causes. Publ. in Met. NO. 59, Arctic Met. Res. Grp., McGill Univ., Montreal, 23 pp. Vowinckel, E. and Orvig, S. (1966), Energy balance of the Arctic. Arctic Ocean. Arch. Met. Geophys. Biokl., B 14: 303-25.
V. The heat budget over the
Vowinckel, E. and Orvig., S. (1970), The climate of the North Polar Basin. In: Orvig, S. (ed.), Climates of the Polar Regions, World Survey of Climatology. Vol. 14, Elsevier, New York, 129-252. Vowinckel, E. and Orvig, S. (1973), Synoptic energy budgets from the Beaufort Sea. Fluxes over Polar Surfaces, W.M.O. Tech. Note No. 129, W.M.O,, Geneva, 145-66.
In:
Energy
Vowinckel, E. and Taylor, B. (1965), Energy balance of the Arctic. IV Evaporation and sensible heat flux over the Arctic Ocean. Arch. Met. Geophys. Biokl. B 14: 36-52. Walsh, J. E. (1977), Empirical orthogonal functions and the statistical predictability of sea ice extent. In: Sea Ice Processes and Models, (Symposium), I.C.S.I./AIDJEX, September 1977, Vol. I I , 98-107. Walsh, J. E. (1978), Temporal and spatial scales of the Arctic circulation Mon. Wea. Rev., 106: 1532-44. Walsh, J. E. and Johnson, C. M. (1979), An analysis of Arctic sea ice fluctuation, 1953-77. J. Phys. Oceanog. (in press). Wendler, G. and Jayaweera, K.O.L.F (1976), Some remarks on the unusual Beaufort-Sea ice conditions in summer 1975. Univ. of Alaska, Geophys. Inst., Rep. UAG R-246, Fairbanks, 28 pp. Wiese, W. (1924), Polareis and atmospharische Schwankungen. Geograf. Ann., 6: 273-99. Wohi, G. M. (1978), A study of sea ice conditions and synoptic climatology for the Beaufort Sea coast of Alaska. Unpub. M.A. thesis, Univ. of Colorado, Boulder, 166 pp.