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Bathymetry of the Arctic Ocean North of 85° N latitude
Tectonophysics, 42 (1977) T27-T33 o Elsevier Scientific Publishing Company,
Amsterdam
-
Printed
T27 in The Netherlands
Letter Section Rathymetry of the Arctic Ocean north of 85’ N latitude*
L. W. SOBCZAK Gravity and Geodynamics Division, Earth Physics Branch, Department and Resources, Ottawa, Ontario KlA OY3 (Canada)
(Submitted
of Energy, Mines
April 25, 1977; accepted June 20, 1977)
ABSTRACT Sobczak, L.W., 1977. Bathymetry physics, 42: T27-T33.
of the Arctic Ocean north of 85”N latitude.
Tectono-
Comparison of a new compilation of avaiiable Arctic bathymetric data north of 85”N latitude with previously published charts shows large discrepancies in the position and morphology of several major Arctic sea-floor features. Near the North Pole the Lomonosov Ridge pinches to a width of about 20 km with very steep slopes. The crest of the Ridge at this location is displaced de&rally by about 80 km. Alao, the crest of this ridge curves towards Ellesmere Island and does not continue towards Greenland. The Marvin Spur is actually a series of knolls or sea mounts with relief varying from 500 to over 1300 m. The 600 km wide arch known as the Alpha Cordillera consists of closed, wide (lo-40 km) elongated (180-260 km) troughs and ridges with relief of over 1000 m. Circular sea mounts and deeps are also noted along this cordillera. The Arctic MidOceanic Cordillera is a rather flat 200 km wide feature that tilts gently upward by about 500 m from the Pole Abyssal Plain to the Barents Abyssal Plain. It is characterized by a series of narrow ridges and troughs usually less Wan 20 km wide with a central deep trough over 5100 m deep and shallow ridges rising to heights of 2600 m. These features generally parallel the Lomonosov Ridge. This cordillera appears to be abruptly truncated along the Greenwich meridian. The Morris Jesup Plateau is a single pronged northeast trending feature with relatively shallow westward slopes and steeply dipping eastward slopes,
INTRODUCTION
Since the turn of the century several bathymetric maps showing the physiography of the floor of the Arctic Ocean have been published. Initially, maps were compiled with very little data such as the one by Nansen (1904) that showed a single basin with depths varying from three to four kilometers. Much later, Emery (1949) using 152 bathymetric soundings compiled a map *Contribution
of the Earth Physics Branch NO. 680.
T28
which also showed a single Arctic Ocean basin with maximum depths in excess of 4500 m but indicated a more irregular basin floor. Since 1949, a considerable amount of bathymetric data has been obtained by several countries and this has led to the publication of progressively more detailed regional bathymetric maps for the whole Arctic Ocean (Link et al., 1960; De Leeuw, 1967; Ritchie, 1969; and Heezen and Tharp, 1975). Unfortunately, even the most recent of these maps still include significant errors. This note describes the initial results of a re-examination of available Arctic bathymetric data and points out gross errors in the position and mor90 ;E
Fig. 1. Bathymetry north of 86” N. American Geographical Society’s map (Heeaen and Tharp, 19’76) is superimposed on the bathym&ry of ‘Fig. 2. Cantour inkrval is=600
m.
T29
phology of the Lomonosov Ridge, Marvin Spur, Alpha Cordillera and the Morris Jesup Plateau north of 85”N latitude that exist on previously published maps, most notably the recent American Geophysical Society (AGS) bathymetric map (Fig. 1) (Heezen and Tharp, 1975).
A new bathymetric map (Fig. 2) was compiled using a data file assembled from about 2400 soundings from the records of the Defense Mapping Agency 90”/ E
. _^... I -3500\
fMakwov
Basin)“
90”
w
Fig. 2. Bathymetry north of 85”N. Contour interval is 500 m. Straight lines indicate location of nuclear submarine traverses from 1957 to 1962 along which water depth echograms were taken (Beal, 1969). Dots indicate spot soundings taken from the sea ice. l-6 are seamounts.
T30
Aerospace Centre (DMAAC) and the Earth Physics Branch (EPB) for the area north of 85”N latitude. In addition, sounding values taken from the GEBCO Chart (De Leeuw, 1967), from the AGS map (Heezen and Tharp, 1975), from the Canadian Oceanographic Data Centre and from echograms (Beal, 1969) were added to the Map. Those data from the AGS map and the echograms which did not agree with the soundings taken from the pack ice were rejected. BATHYMETRIC
FEATURE
Figure 2 was compared with the most recent published map of Arctic Ocean bathymetry (Heezen and Tharp, 1975), partially reproduced in Fig. 1. A number of differences can be noted. 1 Lomonosou Ridge
(a) The crest of the Lomonosov Ridge on the North American side does not strike southward toward central northern Greenland (Fig. 1) but curves westward toward the northern coastline of Ellesmere Island as shown by Link et al. (1960), De Leeuw (1967), Ritchie (1969), Ostenso and Wold (1977) and in Fig. 2. (b) Generally, the Lomonosov Ridge varies from 80 to 100 km in width but at longitude 165” W about 80 km from the North Pole the ridge~pinches to about 20 km width with very steep slopes. At this location there is an abrupt bend in the ridge and the Eurasian side is dextrally offset about 80 km from the ridge on the North American side. (c) The extension of the Lomonosov Ridge to the Eurasian Continent is in agreement with Heezen and Tharp (1975). However, Ritchie (l%%%)mislocated the crest of this part of the ridge by 10, 90 km towards the Fletcher Abyssal Plain. 2 Marvin Spur
The Marvin Spur located at the eastern end of the Fletcher Abyssal Plain (Fig. 1) is in fact a series of sea mounts (Fig. 2) that rise about 1000 m (Table I) above the floor of the Fletcher Abyssal Plain and lie along the axis of the Makarov Basin parallel to and about 80 km to the southwest of the Lomonosov Ridge. At the extreme southeastern end of the Makarov Basin, sea mount No. 6 (Fig. 2) is very extensive and abuts the northeastern end of the Alpha Cordillera. It broadens to the south but to the northwest it pinches out and perhaps forms a separate feature, the crest of which pqa&?ls the Lomonosov Ridge. The Marvin Sea Mounts may extend further to the northwest from Sea Mount No. 1 along the axis of the Makarov but its extension is unaxtain bemu& no detailed soundings bve been takea in this region.
T31
TABLE I Position
and water depths of the Marvin Sea Mounts
Sea Mount No.
Latitude W)
Longitude W)
minimum depth (m)
Surrounding depth (m)
Difference (m)
1 2 3 4 5 6
87” 50’ 88” 15’ 88’10’ 88” 30’ 88” 40’ 87’45’
175” 167” 155” 143” 127” 86”
2998 3400 2487 3100 2830 1435
=3950 -3900 -3800 -3900 =3900 ~2700
952 500 1313 800 1070 1265
3 Alpha Cordillera Although the Alpha Cordillera shown in Fig. 2 grossly follows the outlines shown on Fig. 1, Fig. 2 shows a much more rugged topography for the area between longitude 9O”W and 175”E and latitude 85”N to about 87 112”N. In the wide part of the Alpha Cordillera along about 13O”W longitude, the submarine trough at approximately 86”N latitude shown as open to the west (Fig. 1) is actually a closed depression some 180 km long with a knoll (1400 m high on Profile 2 (p. 193) of Beal, 1969) separating it from the Fletcher Abyssal Plain. This depression which is also shown by De Leeuw (1967) is nearly 2300 m deep and is flanked by two ridges 200-220 km long and lb 40 km wide. These ridges are not present in Fig. 1. Other discrepancies exist. For example, along about 16O’W longitude, the northern flank of the cordillera changes direction by nearly 90” and shifts about 160 km southward as though sinistrally offset. The cordillera also continues further to the west, to at least 175”E longitude, than is indicated in Fig. 1. Several circular knolls and deeps also appear to be present within the cordillera (Fig. 2). 4 Morris Jessup Plateau This plateau is neither a two-pronged feature nor a feature with moderate slopes on all sides (Heezen and Tharp, 1975). It appears to be a single plateau with a moderate slope on the western side and a very steep slope on the eastern side. In fact, Ostenso and Wold (1977) show the eastern side as a nearly vertical step of about 3000 m. Figure 2 shows the Morris Jesup Plateau extending eastward so that the 4000 m bathymetric contour will agree with a submarine track plotted by Beal (1969). However, this feature may extend northward instead as ba~ymet~c control in this locality is poor.
T32
5 Arctic Mid-Oceanic Cordillera (Nansen or Gakkel Ridge) The Arctic Mid-Oceanic Cordillera is not a typical mid-oceanic ridge as modelled by Heezen and Tharp (1975). The available sounding data over this feature are shown by straight lines representing submarine traverses and by dots for the individual soundings (Fig. 2). The cordillera is not a broad arcuate zone similar to the Mid-Atlantic Ridge but is a rather flat tilted regional feature that rises 300-500 m from the Pole Abyssal Plain at a depth of about 4300 m to the &rents Abyssal Plain at a depth of about 3800 m. This cordillera consists of steep narrow ridges and troughs above and below this sloping flat plain (Figs. 2 and 3). It was patterned by Heezen and Tharp (1975) using the Mid-Atlantic Ridge as a model (M. Tharp, personal communication, 1977). The cordillera as shown in Fig. 1 is therefore largely diagrammatic. The bathymetric data show a prominent narrow central trough (maximum depth 5179 m) towards the southwest end of the cordillera with alternating narrow ridges and troughs (20 km wide) to either side. This cordillera strikes more or less parallel to the Lomonosov Ridge and appears to be abruptly truncated between 0 and 2’E longitude. 85’ I
A.
NORTH POLE ‘0
Meters
.’
Fig. 3. An echogram taken on-board the nuclear submarine 10”E (Profile No. 1, p. 193, after Beal, 1969).
Skate in 1956 along longitude
ACKNOWLEDGEMENTS
The author is pa&icularly grateful to Drs. E.J. Hauer, H.L. Kuykendall and T.O. Seppelin, all of the Defense k&pping Agency Aerospace C@ntre, for the magnetic tapes of digitiqeclpri@pal ledactsmty data, to Miss NI. Tharp for a frank discussian of the of Lamont-Doherty 75), and to Dr. MA. Beal of bathymetay published a d&&xl cliacuqion of the the Arctic Submarine The a&&or ia alao &&b&d nuclear submarine and to Dm. J.F. Sweeney, to Mr. B. Draper for the R.L. Coles, R.A. Gibb and J.G. Tanner, Messrs. R.J. Wetmiller, D.A. Fursyth and J.M. DeLaurier for comments and editing of this report.
T33
REFERENCES Beal, M.A., 1969. Bathymetry and Structure of the Arctic Ocean. Ph.D. thesis, Oregon State University, pp. 205. De Leeuw, M.M., 1967. New Canadian bathymetric chart of the western Arctic Ocean, north of 72”. Deep-Sea Res., 14: 489-504. Emery, K.O., 1949. Topography and sediments of the Arctic Ocean. J. Geo!., 57: 512-521. Heezen, B.C. and Tharp, M., 1975. Map of the Arctic Region. American Geographical Society, Lamont-Doherty Geological Observatory, Columbia University. Link, T.A., Downing, J.A., Roasch, G.0, Byrne, A.W., Wilson, D.W.R. and Reece, A., 1960. Geological map of the Arctic. Alberta Society of Petroleum Geologists, Calgary, Alberta. Nansen, F., 1904. The bathymetrical features of the North Polar Seas. In: F. Nansen (editor), The Norwegian North Polar Expedition, 1893-1896. Vol. 4, Ch. 13. Longmans and Green, London, p. l-232. Ostenso, N.A. and Wold, R.J., 1977. A seismic and gravity profile across the Arctic Ocean Basin. Tectonophysics, 37: l-24. Ritchie, G.S., 1969. North Polar Chart, No. 4006. Hydrographer of the Navy, Taunton, England.
Amsterdam
-
Printed
T27 in The Netherlands
Letter Section Rathymetry of the Arctic Ocean north of 85’ N latitude*
L. W. SOBCZAK Gravity and Geodynamics Division, Earth Physics Branch, Department and Resources, Ottawa, Ontario KlA OY3 (Canada)
(Submitted
of Energy, Mines
April 25, 1977; accepted June 20, 1977)
ABSTRACT Sobczak, L.W., 1977. Bathymetry physics, 42: T27-T33.
of the Arctic Ocean north of 85”N latitude.
Tectono-
Comparison of a new compilation of avaiiable Arctic bathymetric data north of 85”N latitude with previously published charts shows large discrepancies in the position and morphology of several major Arctic sea-floor features. Near the North Pole the Lomonosov Ridge pinches to a width of about 20 km with very steep slopes. The crest of the Ridge at this location is displaced de&rally by about 80 km. Alao, the crest of this ridge curves towards Ellesmere Island and does not continue towards Greenland. The Marvin Spur is actually a series of knolls or sea mounts with relief varying from 500 to over 1300 m. The 600 km wide arch known as the Alpha Cordillera consists of closed, wide (lo-40 km) elongated (180-260 km) troughs and ridges with relief of over 1000 m. Circular sea mounts and deeps are also noted along this cordillera. The Arctic MidOceanic Cordillera is a rather flat 200 km wide feature that tilts gently upward by about 500 m from the Pole Abyssal Plain to the Barents Abyssal Plain. It is characterized by a series of narrow ridges and troughs usually less Wan 20 km wide with a central deep trough over 5100 m deep and shallow ridges rising to heights of 2600 m. These features generally parallel the Lomonosov Ridge. This cordillera appears to be abruptly truncated along the Greenwich meridian. The Morris Jesup Plateau is a single pronged northeast trending feature with relatively shallow westward slopes and steeply dipping eastward slopes,
INTRODUCTION
Since the turn of the century several bathymetric maps showing the physiography of the floor of the Arctic Ocean have been published. Initially, maps were compiled with very little data such as the one by Nansen (1904) that showed a single basin with depths varying from three to four kilometers. Much later, Emery (1949) using 152 bathymetric soundings compiled a map *Contribution
of the Earth Physics Branch NO. 680.
T28
which also showed a single Arctic Ocean basin with maximum depths in excess of 4500 m but indicated a more irregular basin floor. Since 1949, a considerable amount of bathymetric data has been obtained by several countries and this has led to the publication of progressively more detailed regional bathymetric maps for the whole Arctic Ocean (Link et al., 1960; De Leeuw, 1967; Ritchie, 1969; and Heezen and Tharp, 1975). Unfortunately, even the most recent of these maps still include significant errors. This note describes the initial results of a re-examination of available Arctic bathymetric data and points out gross errors in the position and mor90 ;E
Fig. 1. Bathymetry north of 86” N. American Geographical Society’s map (Heeaen and Tharp, 19’76) is superimposed on the bathym&ry of ‘Fig. 2. Cantour inkrval is=600
m.
T29
phology of the Lomonosov Ridge, Marvin Spur, Alpha Cordillera and the Morris Jesup Plateau north of 85”N latitude that exist on previously published maps, most notably the recent American Geophysical Society (AGS) bathymetric map (Fig. 1) (Heezen and Tharp, 1975).
A new bathymetric map (Fig. 2) was compiled using a data file assembled from about 2400 soundings from the records of the Defense Mapping Agency 90”/ E
. _^... I -3500\
fMakwov
Basin)“
90”
w
Fig. 2. Bathymetry north of 85”N. Contour interval is 500 m. Straight lines indicate location of nuclear submarine traverses from 1957 to 1962 along which water depth echograms were taken (Beal, 1969). Dots indicate spot soundings taken from the sea ice. l-6 are seamounts.
T30
Aerospace Centre (DMAAC) and the Earth Physics Branch (EPB) for the area north of 85”N latitude. In addition, sounding values taken from the GEBCO Chart (De Leeuw, 1967), from the AGS map (Heezen and Tharp, 1975), from the Canadian Oceanographic Data Centre and from echograms (Beal, 1969) were added to the Map. Those data from the AGS map and the echograms which did not agree with the soundings taken from the pack ice were rejected. BATHYMETRIC
FEATURE
Figure 2 was compared with the most recent published map of Arctic Ocean bathymetry (Heezen and Tharp, 1975), partially reproduced in Fig. 1. A number of differences can be noted. 1 Lomonosou Ridge
(a) The crest of the Lomonosov Ridge on the North American side does not strike southward toward central northern Greenland (Fig. 1) but curves westward toward the northern coastline of Ellesmere Island as shown by Link et al. (1960), De Leeuw (1967), Ritchie (1969), Ostenso and Wold (1977) and in Fig. 2. (b) Generally, the Lomonosov Ridge varies from 80 to 100 km in width but at longitude 165” W about 80 km from the North Pole the ridge~pinches to about 20 km width with very steep slopes. At this location there is an abrupt bend in the ridge and the Eurasian side is dextrally offset about 80 km from the ridge on the North American side. (c) The extension of the Lomonosov Ridge to the Eurasian Continent is in agreement with Heezen and Tharp (1975). However, Ritchie (l%%%)mislocated the crest of this part of the ridge by 10, 90 km towards the Fletcher Abyssal Plain. 2 Marvin Spur
The Marvin Spur located at the eastern end of the Fletcher Abyssal Plain (Fig. 1) is in fact a series of sea mounts (Fig. 2) that rise about 1000 m (Table I) above the floor of the Fletcher Abyssal Plain and lie along the axis of the Makarov Basin parallel to and about 80 km to the southwest of the Lomonosov Ridge. At the extreme southeastern end of the Makarov Basin, sea mount No. 6 (Fig. 2) is very extensive and abuts the northeastern end of the Alpha Cordillera. It broadens to the south but to the northwest it pinches out and perhaps forms a separate feature, the crest of which pqa&?ls the Lomonosov Ridge. The Marvin Sea Mounts may extend further to the northwest from Sea Mount No. 1 along the axis of the Makarov but its extension is unaxtain bemu& no detailed soundings bve been takea in this region.
T31
TABLE I Position
and water depths of the Marvin Sea Mounts
Sea Mount No.
Latitude W)
Longitude W)
minimum depth (m)
Surrounding depth (m)
Difference (m)
1 2 3 4 5 6
87” 50’ 88” 15’ 88’10’ 88” 30’ 88” 40’ 87’45’
175” 167” 155” 143” 127” 86”
2998 3400 2487 3100 2830 1435
=3950 -3900 -3800 -3900 =3900 ~2700
952 500 1313 800 1070 1265
3 Alpha Cordillera Although the Alpha Cordillera shown in Fig. 2 grossly follows the outlines shown on Fig. 1, Fig. 2 shows a much more rugged topography for the area between longitude 9O”W and 175”E and latitude 85”N to about 87 112”N. In the wide part of the Alpha Cordillera along about 13O”W longitude, the submarine trough at approximately 86”N latitude shown as open to the west (Fig. 1) is actually a closed depression some 180 km long with a knoll (1400 m high on Profile 2 (p. 193) of Beal, 1969) separating it from the Fletcher Abyssal Plain. This depression which is also shown by De Leeuw (1967) is nearly 2300 m deep and is flanked by two ridges 200-220 km long and lb 40 km wide. These ridges are not present in Fig. 1. Other discrepancies exist. For example, along about 16O’W longitude, the northern flank of the cordillera changes direction by nearly 90” and shifts about 160 km southward as though sinistrally offset. The cordillera also continues further to the west, to at least 175”E longitude, than is indicated in Fig. 1. Several circular knolls and deeps also appear to be present within the cordillera (Fig. 2). 4 Morris Jessup Plateau This plateau is neither a two-pronged feature nor a feature with moderate slopes on all sides (Heezen and Tharp, 1975). It appears to be a single plateau with a moderate slope on the western side and a very steep slope on the eastern side. In fact, Ostenso and Wold (1977) show the eastern side as a nearly vertical step of about 3000 m. Figure 2 shows the Morris Jesup Plateau extending eastward so that the 4000 m bathymetric contour will agree with a submarine track plotted by Beal (1969). However, this feature may extend northward instead as ba~ymet~c control in this locality is poor.
T32
5 Arctic Mid-Oceanic Cordillera (Nansen or Gakkel Ridge) The Arctic Mid-Oceanic Cordillera is not a typical mid-oceanic ridge as modelled by Heezen and Tharp (1975). The available sounding data over this feature are shown by straight lines representing submarine traverses and by dots for the individual soundings (Fig. 2). The cordillera is not a broad arcuate zone similar to the Mid-Atlantic Ridge but is a rather flat tilted regional feature that rises 300-500 m from the Pole Abyssal Plain at a depth of about 4300 m to the &rents Abyssal Plain at a depth of about 3800 m. This cordillera consists of steep narrow ridges and troughs above and below this sloping flat plain (Figs. 2 and 3). It was patterned by Heezen and Tharp (1975) using the Mid-Atlantic Ridge as a model (M. Tharp, personal communication, 1977). The cordillera as shown in Fig. 1 is therefore largely diagrammatic. The bathymetric data show a prominent narrow central trough (maximum depth 5179 m) towards the southwest end of the cordillera with alternating narrow ridges and troughs (20 km wide) to either side. This cordillera strikes more or less parallel to the Lomonosov Ridge and appears to be abruptly truncated between 0 and 2’E longitude. 85’ I
A.
NORTH POLE ‘0
Meters
.’
Fig. 3. An echogram taken on-board the nuclear submarine 10”E (Profile No. 1, p. 193, after Beal, 1969).
Skate in 1956 along longitude
ACKNOWLEDGEMENTS
The author is pa&icularly grateful to Drs. E.J. Hauer, H.L. Kuykendall and T.O. Seppelin, all of the Defense k&pping Agency Aerospace C@ntre, for the magnetic tapes of digitiqeclpri@pal ledactsmty data, to Miss NI. Tharp for a frank discussian of the of Lamont-Doherty 75), and to Dr. MA. Beal of bathymetay published a d&&xl cliacuqion of the the Arctic Submarine The a&&or ia alao &&b&d nuclear submarine and to Dm. J.F. Sweeney, to Mr. B. Draper for the R.L. Coles, R.A. Gibb and J.G. Tanner, Messrs. R.J. Wetmiller, D.A. Fursyth and J.M. DeLaurier for comments and editing of this report.
T33
REFERENCES Beal, M.A., 1969. Bathymetry and Structure of the Arctic Ocean. Ph.D. thesis, Oregon State University, pp. 205. De Leeuw, M.M., 1967. New Canadian bathymetric chart of the western Arctic Ocean, north of 72”. Deep-Sea Res., 14: 489-504. Emery, K.O., 1949. Topography and sediments of the Arctic Ocean. J. Geo!., 57: 512-521. Heezen, B.C. and Tharp, M., 1975. Map of the Arctic Region. American Geographical Society, Lamont-Doherty Geological Observatory, Columbia University. Link, T.A., Downing, J.A., Roasch, G.0, Byrne, A.W., Wilson, D.W.R. and Reece, A., 1960. Geological map of the Arctic. Alberta Society of Petroleum Geologists, Calgary, Alberta. Nansen, F., 1904. The bathymetrical features of the North Polar Seas. In: F. Nansen (editor), The Norwegian North Polar Expedition, 1893-1896. Vol. 4, Ch. 13. Longmans and Green, London, p. l-232. Ostenso, N.A. and Wold, R.J., 1977. A seismic and gravity profile across the Arctic Ocean Basin. Tectonophysics, 37: l-24. Ritchie, G.S., 1969. North Polar Chart, No. 4006. Hydrographer of the Navy, Taunton, England.