EGOROV S.A., ZABAVNIKOV V.B., ZYRYANOV S.V., LISOVSKY A.S. Polar Research Institute of Marine Fisheries and Oceanography, Russia

In August/September 2002-2005, PINRO specialists carried out complex air research over the Barents Sea within the frameworks of annual joint Russian-Norwegian ecosystem surveys.

The complex air surveys were aimed at control of ice conditions including searching for icebergs, as well as monitoring of ecological situation in the Barents Sea and others.

During control of ice conditions and observation of icebergs, the following main parameters were registered:
- Location and spatial structure of ice edge;
- Compacting of ice in the edge zone with the account of age and form of ice formations;
- Above-water form and sizes of icebergs.

When monitoring the ecological situation, the following main characteristics were registered:
- Thermal conditions on the sea surface, including temperature measurements along the air survey route;
- Clarity of the sea as an indicator of water turbidity along the air survey;
- Concentration of "a" chlorophyll on the sea surface and plankton in the surface layers along the air survey route;
- Registration of all kinds of contamination including oil films along the air survey route and in lane of view up to 2 km
- Distribution and abundance of marine mammals and birds by their species composition along the air survey route and in the lane of view equal to doubled altitude of the survey.

All discussed air surveys were carried out by the same technology, from the board of aircraft AN-26 "Arktika" (SL), with the use of the same technical means of air sounding, processing and presenting data (including software). Since air surveys were carried out in the same or adjacent areas and in the identical periods, they can be considered as monitoring surveys (Zabavnikov and Lisovsky, 2004).

Directly in the area of the Shtockman condensed gas field (SCGF) the complex air surveys were performed on 25 August 2003 and 27 August 2004 as an element of ecosystem air investigations in the eastern part of the sea limited by position 72°00' - 74°00,N/41°30,E - coastal waters of Novaya Zemlya and 72°30' - 75°00,N/41°00' - 47°00'E, correspondingly. The summarized obtained results are as follows:

1. Thermal conditions on the sea surface during both surveys were higher than climatic ones by 3-3.5°C in 2003 and by 4-4.5°C in 2004. Mean values of SST in 2004 in the mentioned period were 0.5-0.8°C higher than in 2003 under the identical spatial structure of SST.

2. Clarity of the sea in 2004 was in general also higher than in 2003. And in 2004 its values over the whole SCGF were practically the same and constituted 11 to 14 m, and in 2003 clarity increased to the north varying from minimal values of 5-7 m in the south to 10-12 m in the north.

3. During air surveys, values of "a" chlorophyll and on the sea surface and plankton in the pre-surface layers were mainly constant; no local areas with heightened values of concentrations were registered. Because of the absence of blossoming, mean values of the surface "a" chlorophyll did not exceed 0.9 mg/m , and pre-surface plankton - 350 mg/m .

4. The year of 2004 was characterized by great number of sea mammals and birds compared to 2003. In 2004 in the area of SCGF more than 1 500 birds of different species with kittiwake predominated (about 60 %) were registered, as well as 14 seals, 85 dolphins and more than 300 whales (minke whale, predominantly).

5. During both air surveys, no contamination (wood residue and other wastes), as well as films of organic origin, was revealed.

Summarizing mentioned above circumstances, we could conclude that the ecological situation during air surveys in the area of SCGF was stably good.

During air survey of 2004, the waters of the North Atlantic predominated there compared to the same period of 2003.

Now about ecological and ice conditions in the area adjacent to SCGF, first of all, from the north (icebergs and ice conditions).

As is well known, the main resource of danger during oil and gas extraction in the SCGF is icebergs, which are predominantly formed on islands of Spitsbergen, Franz Josef Land and in the north of the Novaya Zemlya and can be transferred into the area of the Stockman field by cold northern currents, mainly by some branches of the Central Current. A maximal southern border of icebergs distribution is directed along latitudes between 74° and 75° N from the Bear Island to the Novaya Zemlya archipelago. Icebergs can be revealed there in some cold years in November. However, since the discussed in the paper period of research is a period of heightened level of heat content of pre-surface waters in the Barents Sea compared to the long-term mean level, the appearance of icebergs in that period is excluded during the whole year. Icebergs were revealed only close to the eastern coast of the Spitsbergen archipelago and nearby Franz Josef Land; in the other territory they were not revealed.

Nevertheless, in the case of cooling in the Barents Sea area, the probability of icebergs appearance in the area of SCGF increases very much, that requires to organize and to perform a regular monitoring of icebergs. And it should be remembered that since the above-water part of icebergs in the Barents Sea is small compared to icebergs of Greenland, they can be revealed and identified for sure only with the use of aircraft radiolocation with the subsequent photographing; methods of satellite radiolocation are not effective in this case.

As for the ice conditions the following thing should be mentioned. It is known that under the all year round exploitation of SCGF it can be covered by sea drifting ices in some cold years. And there are information that in the coldest years in the period of maximal development of ice coverage in the Barents Sea (April-May) the edge of drifting ice was along 72° - 73° N from 20°E to 40°E-43°E turning further to the south and reaching the Kola Peninsula nearby estuary of the Rynda River. In the early autumn, September/October, the Barents Sea area is maximally free from ice. Usually, the border of drifting ices at that time is directed along the latitude between 77° - 78° N distributing from the eastern coast of Spitsbergen archipelago eastwards, in the south of Franz Josef land and further to the Kara Sea.

Long-term mean location of the ice edge (keeping its main spatial orientation) begins from the southern extremity of Spitsbergen archipelago, stretches further to the east between 75° - 76° N to 48°- 51°E and turns then to the south reaching the cape Svyatoy Nos on the northeastern extremity of the Kola Peninsula. Under mentioned circumstances it is necessary to monitor regularly the ice conditions in the area of SCGF and adjacent areas of the Barents Sea with the use of data of the satellite sounding (optical and all-weather radiolocation data), which will permit to assess general ice situation, and results of mesoscale air surveys (materials of optical and radiolocation sounding). Such approach was partly tested in 2002-2005 for the period, when the sea area was maximally free from the ice.

The obtained results permit to add reasonably the above inference and to make the main conclusions. In spite of the fact that all four discussed years are referred to the category of warm years by their pre-surface water heat content and mean air temperature for September, the ice edge in the same area in the north of the Barents Sea was located in different latitudes, although the spatial character of its distribution from year to year was similar. The northernmost location of the ice edge was registered in 2004, when it located predominantly in the latitudinal direction along 81°45' - 82°00'N between 20°E and north of the Franz Josef Land, i.e. sufficiently more to the north than the long-term mean location in the period, when the Barents Sea is maximally free from the ice.

The southernmost location of the drifting ice edge was registered in 2003, when it located by the end of the air surveys along 73°30'N from the eastern extremity of the Edge Island to 45°N. However, in the middle of the month the ice was located much farmer to the north, and the edge was oriented in the latitudinal direction between 78°30'-79°00'N. This circumstance shows that the ice forms actively in the north of the Barents Sea in the end of September, therefore, it is necessary to organize and perform regular monitoring of ice conditions. The years of 2002 and 2005 by their ice conditions are in between 2004 and 2005. However, there were certain differences. In total, the largest part of the ice edge in 2002 located more to the south (by 50-60 miles) than in 2005 stretching along the latitude between 79°00'-79°15'N. The drifting ice edge from the northeastern coast of the Spitsbergen archipelago (the Northeastern Land island) to the Bely Island was in 2005 farther to the south than in 2002 by 45-60 miles on average.

Mean values of SST and thermal conditions in the pre-surface water layers in the northern parts of the Barents Sea adjacent to the SCGF were higher than long-term means during September for 2002-2005 by 3.2°-4.2°C, 3.0°-4.0°C, 4.0°-5.0°C and 3.5°- 4.5°C, correspondingly. As it seen from the presented data, there were certain differences between years. The warmest year by thermal content of the pre-surface waters was 2004, the coldest - 2003; and the years of 2002 and 2005 occupied intermediate location. The similar situation was registered directly in the Shtockman field and concerned the character and specific features of the ice conditions (see above).

Water clarity values in the northern areas of the Barents Sea adjacent to the SCGF were within the norm or somewhat higher. Range of water clarity variation was different from year to year. Maximal range was registered in 2004, it constituted 6-23 m, and minimum was in 2003 (6-18 m). The years of 2002 and 2005 were in-between position; the range of variation constituted, correspondingly, 7-23 and 6-20 m. A specificity of distribution of water clarity values was that the closer to the ice edge, the higher clarity, excluding the coastal waters. Considering water clarity like an indirect indicator of water turbidity it should be noted coming from the mentioned above that in 2003 in the middle of September the waters were the most turbid in the discussed area, and in 2004 the waters were the most clear. Similar situation was observed in the area of the SCGF.

Year-to-year variability of values of "a" chlorophyll on the sea surface and plankton in the pre-surface layers was generally insufficient in the discussed period and area (it is caused by the absence of blooming), and the spatial character of distribution was identical. The specificity was that the farther to the south and west, the higher concentrations of the mentioned parameters. They diminished closer to the edge. For example, mean values of the surface "a" chlorophyll close to SCGF did not exceed 0.9 mg/m , and the pre-surface plankton - 350 mg/m.

During investigations the densest concentrations of sea mammals and birds in the northern areas of the Barents Sea adjacent to the SCGF were observed in sites of heightened concentrations of capelin and polar cod, the main pelagic fish species, which are one of the main resources of the food base for sea mammals and birds. However, their abundance per unit of the surveyed way (1000 km) differed from year to year (this characteristic should be considered as an index). It is impossible to compare total abundance, since the extension of all tacks and total duration of surveys were unequal in different years. The most numerous species of sea mammals was harp seal, which formed its main concentrations close to the ice edge. Their maximum index of abundance was registered in 2002; after that it began to diminish. Between 2002 and 2003 diminishing was gradual, and between 2003 and 2004 it was jumping.

The index reached its minimum in 2005 (it changed from 157 to 52 for the discussed period). Indices of abundances of the rest species of sea mammals (whales, killer whale, dolphins, white whale, ringed seal, bearded seal, walrus) had variations from year to year with different signs; they either increased or decreased. The most often found species were whales (minke whale and humpback whale, predominantly) and dolphins, which were observed over the vast areas. As for density of minke whale and humpback whale the areas of the Hopen Island and Bear Island should be mentioned, as well as the central part of the Barents Sea, including a part of the SCGF. As for dolphins, the distribution area was somewhat wider and occupied the area from the Spitsbergen archipelago to SCGF. The most often occurred species of dolphins was white-beaked dolphin. The specific feature of distribution and abundance of sea mammals is a sharp increase of abundance of white whale north of SCGF in 2004 and walruses in the pre-edge zone in 2005. After a sufficient growth of index of white whale abundance a sheer fall of it next year took place. The most often occurred bird species in the discussed area are kittiwake and fulmar (totally 80-90%).

However, kittiwake dominates in this combination. A decrease of birds abundance index from 4 877 in 2002 to 454 in 2004 was registered. However, by the year of 2005 a sharp increase of this parameter has happened, and it almost reached the level of 2002. The similar situation was in the Norwegian Sea and off Great Britain coast. The reason was not revealed completely. At present, a profound systematic analysis of the obtained materials and data is carried out.

No sufficient contamination neither of organic origin, nor industrial debris, was revealed during investigations.

The presented materials permit to conclude that in connection with the beginning of the industrial exploitation of the SCGF and transportation of its products over the Barents Sea area, including the important fishing grounds, it is necessary to organize and perform a regular year-round monitoring of ice conditions, including searching for icebergs, as well as ecological situation, including the whole multiplicity of all the components. The monitoring should be based on materials of air and space surveys in their combination and supplementation. Expenditures for organization and performance of such works, which seem to be large, are much less than losses, which can happen in the case of accidents.

References
Zabavnikov, KB. And Lisovsky A.S. Aircraft-laboratory AN-26 "Arktika" as a platform of monitoring of the ecological situation. Materials of the international conference "Oil and Gas of the Arctic Shelf 2004". P. 97-1001.

OIL AND GAS OF ARCTIC SHELF 2006 (PROCEEDINGS OF INTERNATIONAL CONFERENCE)