Spatial and temporal anomalies of chlorophyll concentration in atlantic ocean (by space-based data)

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Pergamon

www.elsevier.com/loca~e/asr

Adv. Space Res. Vol. 30, No. 11, pp. 2541-2546, 2002 © 2002 COSPAR. Published by Elsevier Science Ltd. All fights reserved Printed in Great Britain 0273-1177102 $22.00+ 0.00 PII: S0273-1177(02)00378-2

SPATIAL AND TEMPORAL ANOMALIES OF CHLOROPHYLL CONCENTRATION IN ATLANTIC OCEAN (BY SPACE-BASED DATA) A.Shevyrnogov1, G.Vysotskaya2 and E. Shevyrnogov1

llt~titute of Biophysics of SB RAS, Krasnoyarsk,Russia. [email protected] 2Instituteof ComputationalModellingof SB RAS, Krasnoyarsk, Russia

ABSTRACT The work presents long-standing CZCS-satellite-based data about spatial distribution of anomalies in chlorophyll concentration and lemperature of the ocean. An anomaly criterion is proposed. Maps of Atlantic ocean areas with elevated probability of anomalies are given. Properties of anomalous zones in different parts of the Atlantic ocean are discussed. Satellite-based maps of anomaly coefficients for chlorophyll concentration and temperature in the Atlantic ocean have been shown to feature substantial differences, the zones of elevated anomaly of chlorophyll concentration and temperature - to be close only in the vicinity of the Amazon outflow into the Atlantic ocean. Along with fundamental knowledge about dynamics of biological phenomena in the ocean the methods described may be used to reveal deviations due to anthropogenic impact. The methods presented may be used to process SeaWiFS prograna data. The data derived may be used to analyze long-standing time serie~ to estimate randomness of cunent changes. © 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

INTRODUCTION Continuous monitoring of phytopigment concentrations in the ocean by space-borne methods makes possible to estimate ecological condition of bioeenoses in critical areas. As opposed to land vegetation, phytoplankton dynamics is largely determined by hydrological processes which may be either recurrent or random (R.R. Bidigare and M.E. Ondrusek, 1996); (K.L. Denman and M.R. Abbott, 1988); (T. Dickey et al., 1991). In principle, the types of chlorophyll concentration dynamics can manifest as zones quasistationary by seasonal chlorophyll dynamics, long-standing variations of phytopigrnent concentrations, anomalous variations, etc. (A.P. Shevyrnogov and G.S. Vysotskaya, 1998), (A.P. Shevyrnogov et al., 1996). While large-scale and frequently occurring phenomena have been much studied, the seldom occurring changes of smaller scale may be of interest for the analysis of long-term processes and rare natural variations. Along with this, the ability to reflect effect of anthropogenous impact or natural ecological disasters on the ocean biota makes the anomalous variations ecologically interesting. Close interoannection of chlorophyll concentration distribution with hydrological processes makes important concurrent analysis of the variability of temperature fields. METHODS The main objective of this work is to determine the anomaly criteria of the characteristics inferred from satellites. The anomaly criterion taken in this work is a difference between maximum outlier and average value The research described in this publication was supported by grants REC-002 (US-CRDF), INTAS-97-OPEN-519 and RFBR No. 99--05-64338. 2541

2542

A. Shevyrnogov et al.

normalized to the standard deviation (with distribution asymmetry considered for chlorophyll). As initial material for the analysis we used monthly composites of Coastal Zone Color Scanner (CZCS) chlorophyll concentration data (1979-1985). These data were received by the Institute of Biophysics from the Jet Propulsion Laboratory during the joint work of working group "Earth Sciences".

Ace,, (x, y) = Cch'~ (x, y) -Cc/a(x, y) O'cch,(x, y ) where

ACcht is the anomaly criterion;

Ccht,.. (X, y) is the maximum chlorophyll concentration during the measurement period; Ccht (x, y) is the average chlorophyll concentration during the measurement period; (7Cc/,t (X, y )

is the standard deviation of chlorophyll concentration, all values are calculated for

neighborhood 3x3 with center x,y and all images of the data set. From the given expression it is apparent that the anomaly criterion developed is most sensitive in the areas with small absolute concentrations. These areas are the tropical and subtropical areas of the Global ocean.

WgO

°

60 °

30 °

0 °

Fig. 1. Space distribution of anomaly coefficient for chlorophyll concentration in the Atlantic ocean. Points with anomaly coefficient more than 3 are revealed. The darker colors mean higher values of anomaly coefficient. Analyses of this characteristic makes possible to discover areas with rare deviations of chlorophyll concentrations and temperature. This method also makes possible to disclose areas with particularly stable characteristics, when stability means both small variability (small standard deviation of chlorophyll concentration) and periodic (e.g. seasonal) changes even though with high amplitude. When amplitude is high, but standard deviation is also high, an anomaly coefficient is low. For the areas with high variability of chlorophyll concentration the anomalous deviations can, probably, be deduced with adequate account of the periodic component in the time series.

A n o m a l i e s Of C h l o r o p h y l l C o n c e n t r a t i o n

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2543

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Fig.2 Space distribution of anomaly coefficient for chlorophyll com~ntration in the Atlantic ocean (zone

1).

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Fig.3 Space distribution of anomaly coefficient for chlorophyll concentration in the Atlantic ocean (zone 2).

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Fig. 4. Space distribution of anomaly coefficient for chlorophyll concentration in the Atlantic ocean (zone 3).

A software was designed for generation of anomaly coefficient distribution maps. On clicking at the a point of a map this software outputs all values of chlorophyll concentration for this point during all observation period to the screen and a text file. RESULTS The approach described was employed to process C7.CS and AVHRR satellite data during the global flights for 7.5 years, beginning in 1979. The re,suits produced are represented as maps disclosing anomalies of chlorophyll concentration(Figure 1) and temperamrc(Fignre 5). As an example we give a map of space distribution of anomaly coefficients or the surface area of the Atlantic ocean. Different densities denote zones with different anomaly coefficients. R should be noted that the space distribution of the criterion chosen features the following peculiarities: the anomaly coefficient increases in three major zones(Figure 1) over large areas: zone in the tropical and subtropical parts, of the Atlantic ocean from 32.5N to 13N (zone 1); vast zone in the south-west part of the Atlantic ocean limited by 5.5S, 34S and 5W (zone 2); coastal anomaly zone in the vicinity of the Amazon outflow (zone 3); each of the zones is a sum of local spots united in space but separate in time; the local inhomogeneity spots size from 60 to 250 miles; zones of local inhomogeneities differ both in the coefficient amplitude and in size of the area; sometimes local inhomogeneities different in time are united in space, the time, at this, may be close or distant. Specific manifestations of this type are zone 2, points B, B' and C, C'.

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A. Shevyrnogovet al.

Generally the local spots are manifestations of zones that had 1 or 2 substantial oufliers during 6-7 years. The spots uniting local inhomogeneities with different emergence time may be divided into two types - time-close - result of process development or displacement in the space of anomaly occurred; - time-separate - accidental coincidence in space during the measurement period, e.g. points B, B' and C, C' in zone 2. Chlorophyll concentrations in different Atlantic zones exhibit the following features: Zone 1. Analysis of zone 1 (see Figure 2 and Table 1) demonstrates that spots A, B and C are time-separated, meanwhile the emergence time of inhomogeneity inside spots B and C is approximately the same suggesting that responsible for this inhomogeneity is one process. Analysis of anomalies in the first zone demonstrated that major part of them existed no longer than one-two months.

Table 1. Chlorophyll Concentration in the Atlantic Ocean, Zone 1, Points A - 200332q 65°3%V; B - 19°27~ 59°43'; C - 16°59'N 52°16'; D - 270412q 38025 '

30.11.78 31.12.78 31.01.79 28.02.79 31.03.79 30.04.79 30.06.79 31.07.79 31.08.79 30.09.79 31.10.79 30.11.79 31.12.79 31.01.80 31.05.80 30.06.80 31.07.80

A

B

0.017 0.016 0.018 0.015 0.019

0.015 0.015 0.015 0.016 0.015 0.015 0.015

~ 0.019 0.036 0.034 0.022 0.048 0.034 0.015 0.016 0.017

C

A

D

0.016 0.017 0.016: 0.015 0.017 ~ 0.015 0.036 0.015 0.021 0.018 0.018 0.019 0.021 0.021 0.036 0.023 0.023 0.019 0.019 0.015 0.015 0.015 0.019 0.015

31.08.80 31.10.80 30.11.80 30.12.80 31.01.81 30.04.81 131.08.81

!30.09.81 31.10.81 30.11.81 31.12.81 31.01.82 28.02.82 31.03.82 31.08.82 30.09.82 31.10.82

B

C

0.015 0.019 0.02 0.016 0.023 0.023i 0.018 0.018 0.0151 0.027 0.026 0.015 0.015 0.019 0.015 0.016 0.023 0.04 0.024 0.019 0.034 0.029 0.028 0.032 0.026 0.028 0.023 0.015 0.023 0.019 0.015 0.018 0.022 0.02 0.046 0.027 0.026 0.025

D 0.015

0.015 0.015 0.023 0.027 0.021 0.057 0.029 0.017 0.016 0.015 0.019

A 30.11.82 0.032 31.12.82 0.028 31.0L83 0.022 31.03.83 0.018 31.01.84 0.016 29.02.84 0.015 31.03.84 0.015 30.09.84 0.015 31.10.84 0.017 30.11.84 0.018 30.12.84 0.016 31.01.85 0.016 30.09.85 31.10.85 31.12.85 0.015 28.02.86 0.015 30.04.86 0.015

B

C

0.024 0.016 0.029 0.015 0.019 0.015 0.015 ~ 0.016 0.017 0.016 0.018 0.015

0.033 0.027

D

0.015 0.026 0.017

0.015 0.015 0.02 0.021 0.015

0.023 0.015 0.015

0.016 0.017 0.015 0.015

0.015

Table 2. Chlorophyll Concentration in the Atlantic Ocean, Zone 2, Points A - 4°05'N 50°24"~/; B 2°33'N 48°44'W; B' - 1°56'N 48°52'W; C - I°N 47°18'W; C' - 0°38'S 45°23'W; D- 0°48'N 43°57'W

30.11.78 31.12.78 31.01.79 28.02.79 31.03.79 30.04.79 31.05.79 30.06.79 31.07.79 31.08.79 30.09.79 31.10.79 30.11.79 31.12.79

A D.024 3.057 D.025 ~ 3.027 3.041 3.023 D.018 3.092 3.016 3.021 3.03 3.033 3.024

B B' C C' D ).016 0 . 0 2 D.034 ).021 0 . 0 2 9 ).019 0.032 D.038 ).017 13.024 ).024 0.024 ~ ).021 13.02

~0.505

D.032 ).017 13.016

).018 3.019 ).021 ).018 ).021 ).022 ).034 ).037 3.032

3.026 3.018 D.021 3.021 3.02 3.018 3.034 3.046 3.028

0.036 0.029 0.025 0.031 0.018 0.034 0.061 13.054 0.031

).019 13.023 ).019 3 . 0 1 7 ).016 I).017 ).016 0 . 0 2 9 ).023 13.023 ).019 13.027 ).017 13.063 ).035 0 . 0 3 7 ~13.026 ).023 13.023

A 31.01.80 3.04 29.02.80 31.03.80

B

B'

C

C'

D

0.041 3.029 ).018 0.022 D.041 ).032 ).019 0.026 ).037 31.10.80 3.O28 ).021 D.026 ).026 0.021 0.023 31.10.81 30.11.81 1.042 31.12.82 3.021 ).028 0 . 0 4 3.059 ).022 0.021 3.019 31.12.83 30.11.84 3.021 0.046 30.12.84 ).017 D.074 0.019 0.02 31.01.85 0.O46 30.09.85 3.016

Anomalies of ChlorophyllConcentration

2545

Table 3. Chlorophyll Concentration in the Atlantic Ocean, Zone 3, Points A - 10°18'S 3409'W; B- 8054'S 19°17%V; C - 13°14'S 18°27'; O - 16°43'S 17043 '

30.11.78 31.12.78 30.04.79 31.05.79 30.06.79 31.07.79 31.08.79 30.09.79 31.10.79 30.11.79 31.12.79 31.01.80 29.02.80 31.05.80 30.04.81

A B C D 0.015 0.017 ] 0.0161 0.015 0.015 0.022 0.015 0.015 0.015 0.015 0.015 i 0.017 0.015 0.017 0.015 0.015 0.019 0.021 0.019 0.018 0.015 0.017 0.016 0.015 0.015 0.016 0.015 0.015 0.018

.. ;~,~.....

... N

A 31.05.81 0.026 30.06.81 30.11.81 31.12.81 0.015 31.01.82 0.015 28.02.82 0.015 31.03.82 0.017 30.04.821 31.05.82ln

B C D 0.025 0.016 0.017 0.017 0.049 0.019 0.015 0.015 0.015 0.015 0.019 0.015 0.015 0.025 0.017 0.017 0.023 0.023 0.017

30.09.83 31.10.84 0.019 30.11.841 30 12841 0.015 28102185 !

0.054 0.022 . 0.027 0.015 0.022 0.015 0.015 0.015

.

.

.

.

31.03.85 30.06.85 31.07.85 31.08.85 31.10.85 30.11.85 31.12.85 31.01.86 28.02.86 31.03.86 30.04.86 31.05.86 30.06.86

A B C 0.017 0.016 0.016 i 0.022 0.02 ~ 0.019 0.02 0.015 0.015 0.015i 0.026 0.015 0.015 10.015 0.015 0.015 0.015 0.015 0.015 0.016 0.015 0.016 0.0161 0.015

D 0.015 0.016 0.015 0.015 0.015 0.018 0.015 0.015 0.015 0.015 0.015

~ ~°

Fig. :5. Space distribution of anomaly coefficient for temperature in the Atlantic ocean.

Zone 2. The zone is c]aaracteristic of time-different anomalies merging in space in the united map. Point A is specified by a relatively short period of emergence of anomalies (small size) from the beginning of 1979 to the end of October 1979; Point B consists of two parts: anomalous outlier in the northern part was observed at the beginning of 1979, the southern part along with the outlier in the first half of 1979 had an outlier at the beginning of 1986. Point C. consists of two parts: anomalous outlier in the noah-west part was observed at the end of January 1979, in tile south-eastern part in the end of November 1979. In zone D chlorophyll concentration increased at the end of November 1979.

2546

A. Shevyrnogov etal.

Zone 3. The zone is specific in distribution of small-amplitude anomalies over a large area. Analogous methods have been used to disclose anomalous temperature zones. DISCUSSION The anomalous zones discussed exhibit the following features: : presence in the ocean of localized regions with elevated probability of emergence of anomalous zones, in Figure 1- areas 1, 2, 3; - practically time-random emergence of anomalous zones within the areas discussed; - weak interconnection between the chlorophyll concentration anomaly zone and temperature by the satellite data. As an indirect proof of the presence of anomalous zones may be the situation that occurred during the expedition of "Vityaz" research vessel in 1991. In area 1 (crossed east of the Mid-Atlantic Ridge) specific for its slightly variable hydrobiological and hydrological features the author observed a local zone with elevated biological productivity. Analysis demonstrated that satellite-image-based maps of anomaly coefficients in chlorophyll concentrations and temperature in the Atlantic ocean feature substantial differences (Figure 1, 5). It should be noted that the zones with elevated anomaly of chlorophyll concentration and temperature are close only in the vicinity of the Amazon outflow into the Atlantic ocean. The attempt to reveal relationship between the anomalies of temperature and chlorophyll concentration yielded negative result. It can't be ruled out that this is due to insufficient initial data. Different satellites and different satellite equipment made difficult to furnish space and time coincidence of data. CONCLUSIONS It is obvious that the infrequent occurrence in the ocean of random deviations of phytoplankton concentrations and relatively moderate rate of biooceanological measurements gave no way of revealing the phenomenon described. It is the frequency of space surveys and large area of the measurements that make possible to record rare phenomena in the ocean. Along with fundamental knowledge about dynamics of biological phenomena in the ocean the methods described may be used to reveal deviations brought on by anthropogenous impacts. This first analysis demonstrated that to reveal specifics of anomalous zones it is possible to employ other anomaly criteria emphasizing these or those peculiarities of a phenomenon. Correct account of seasonal dynamics in high oceanic latitudes can also afford to reveal anomaly zones there. The methods proposed may be used to process the SeaWiFS data currently incoming from the new satellite. The data to be obtained can be used to analyze long-standing time series to estimate randomness of current processes. R E F E R E N C E S

Bidigare, R.R., M.E. Ondrusek, Spatial and Temporal Variability of Phytoplankton Pigment Distributions in the Central Equatorial Pacific Ocean, Deep-Sea Res., 43, 809-833, 1996. Denman, K.L., and M.R. Abbott, Time Evolution of Surface Chlorophyll Patterns From Cross-Spectrum Analysis of Satellite Color Images, J. Geophys. Res., 93, 6,789-6,798, 1988. Dickey, T., J. Marra, T. Granata, C. Langdon, M. Hamilton, J. Wiggert, D. Siegel, and A. Bratkovich, Concurrent High-Resolution Bio-Optical and Physical Time Series Observations in the Sargasso Sea During the Spring of 1987,J. Geophys. Res., 96, 8,643-8,663, 1991. Shevyrnogov A.P., Vysotskaya G.S., Gitelzon J.I., Quasistationary Areas of Chlorophyll Concentration in the World Ocean as Observed Satellite Data, Adv. Space Res., 18, 7, (7)129-(7.)132, 1996. Shevyrnogov A.P. and Vysotskaya G.S., Observed Trends of Chlorophyll Concentration in the Surface Layer of the Northern and Central Atlantic (1979-1983). Adv. Space Res., 22, 5, 701-704, 1998.