Sea ice effect on marine systems in the Arctic

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Published: February 9, 2010, 3:12 am
Updated: May 7, 2012, 5:51 pm
Author: International Arctic Science Committee
Topic Editor: Mark McGinley
Topics:
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This is Section 9.2.2 of the Arctic Climate Impact Assessment
Lead Author: Harald Loeng; Contributing Authors: Keith Brander, Eddy Carmack, Stanislav Denisenko, Ken Drinkwater, Bogi Hansen, Kit Kovacs, Pat Livingston, Fiona McLaughlin, Egil Sakshaug; Consulting Authors: Richard Bellerby, Howard Browman,Tore Furevik, Jacqueline M. Grebmeier, Eystein Jansen, Steingrimur Jónsson, Lis Lindal Jørgensen, Svend-Aage Malmberg, Svein Østerhus, Geir Ottersen, Koji Shimada

Sea ice (Sea ice in the Arctic) controls the exchange of heat and other properties between the atmosphere (Atmosphere layers) and ocean and, together with snow cover, determines the penetration of light into the sea. Sea ice also provides a surface for particle and snow deposition, a habitat for plankton, and contributes to stratification through ice melt. The zone seaward of the ice edge is important for plankton production and planktivorous fish. For some marine mammals (Implications for biodiversity conservation in the Arctic) sea ice provides a place for birth and also functions as a nursery area.

This section describes features of sea ice that are important for physical oceanographic processes and the marine ecosystem (Arctic marine environments). More detailed information about sea ice is given in Chapter 6 (Sea ice effect on marine systems in the Arctic).

Seasonal cycle (9.2.2.1)

Sea-ice extent in the Arctic has a clear seasonal cycle and is at its maximum (14–15 million km2) in March and minimum (6–7 million km2) in September[1]. There is considerable interannual variability both in the maximum and minimum coverage. In addition, there are decadal and inter-decadal fluctuations in the areal sea-ice extent due to changes in atmospheric pressure patterns and their associated winds, continental discharge, and influx of Atlantic and Pacific waters[2].

At the time of maximum advance, sea ice covers the entire Arctic Basin and the Siberian shelf seas (Fig. 9.2). The warm inflow of Atlantic water keeps the southern part of the Barents Sea open, but in cold years even its shallow areas in the southeast are covered by sea ice (Sea ice in the Arctic). Also, the west coast of Spitsbergen generally remains free of ice. It is here that open water is found closest to the Pole in winter, beyond 81° N in some years[3]. Sea ice from the Arctic Ocean is transported out through Fram Strait and advected southward by the East Greenland Current to cover the entire east coast of Greenland, although in mild winters it does not reach the southern tip of Greenland. In cold years, the sea ice may also extend south to the northern and eastern coasts of Iceland. In most years there is a thin band of sea ice off West Greenland, which is a continuation of the sea ice from East Greenland and is known as "Storis". Only rarely does the Storis meet the dense sea-ice cover of Baffin Bay and Davis Strait to completely surround. The whole of the Canadian Archipelago, as well as Hudson Bay and Hudson Strait are usually ice-covered[4]. The Labrador Shelf is also covered by sea ice and the Labrador Current transports this southward to Newfoundland. Further west, a complete sea-ice cover extends across the arctic coasts of northwestern Canada and Alaska and fills the Bering Sea as far south as the shelf break[5].

Fig. 9.2. Average sea-ice cover in winter based on data from satellite microwave sensors [6]. The illustration shows total sea-ice cover, plus the distribution of its two components; multi-year ice and first-year ice. The multi-year ice represents the minimum sea-ice extent in summer.

In March or April, the sea ice begins to retreat from its low latitude extremes. By May the coast off northeastern Newfoundland is clear, as is much of the Bering Sea. By June the area south of the Bering Strait is ice-free and open water is found in Hudson Bay and at several arctic coastal locations. August and September are the months of greatest retreat. At this time most of the Barents and Kara Seas are free of sea ice as far as the northern shelf break. The Laptev Sea and part of the East Siberian Sea have open water along their coastline. In East Greenland, the ice has retreated northward to about 72–73° N, while Baffin Bay, Hudson Bay, and the Labrador Sea become ice-free. In the Canadian Archipelago the winter fast ice usually breaks up. North of Alaska, some open water is typically found along the coast[7].

By October, new sea ice has formed in areas that were open in summer, especially around the Arctic Ocean coasts, and in November to January there is a steady advance everywhere toward the winter peak.

Fast ice and polynyas (9.2.2.2)

Fast ice grows seaward from a coast and remains in place throughout the winter. Typically, it is stabilized by grounded pressure ridges at its outer edge, and therefore extends to the draft limit of such ridges, usually about 20 to 30 meters (m). Fast ice is found along the whole Siberian coast, the White Sea, north of Greenland, the Canadian Archipelago, Hudson Bay, and north of Alaska.

Polynyas are semi-permanent open water regions ranging in area up to thousands of square kilometers. Flaw leads occur at the border of fast ice when offshore winds separate the drift ice from the fast ice. Polynyas and flaw leads are environmentally important for several reasons[8]:

  • they are areas of high heat loss to the atmosphere;
  • they typically form the locus of sea-ice breakup in spring;
  • they are often locations of intense biological activity; and
  • they are regions of deep-water formation.

Distribution and thickness (9.2.2.3)

From a combination of satellite observations and historical records, the area covered by sea ice in the Arctic during the summer has been reported to have decreased by about 3% per decade during recent decades[9]. Multi-year ice is reported to have declined at an even greater rate; 7% per decade during the last 20 years or approximately 600,000 km2[10]. Combined, these results imply that the area of first-year ice has been increasing. Sea-ice distribution within subregions of the Arctic has also changed dramatically in the past. For example, warming in the Barents Sea in the 1920s and 1930s reduced sea-ice extent there by approximately 15%. This warming was nearly as great as the warming observed over the last 20 years.

In addition to the recent general decrease in sea-ice coverage, submarine observations suggest that the sea ice over the deep Arctic Ocean thinned from an average thickness of about 3.1 m (1958–1976) to about 1.8 m (1993–1997), or about 15% per decade[11]. In addition, the ice thinned at all 26 sites examined. Overall, the arctic sea ice is estimated to have lost 40% of its volume in less than three decades. However, according to some models[12], the submarine observations may have been conducted over part of the ocean that underwent thinning through shifting sea ice in response to changing winds associated with a high Arctic Oscillation (AO) index (see Chapter 2 for descriptions of the AO and the associated North Atlantic Oscillation). Thus, the conclusion of reduced sea-ice thickness, while valid for the domain of submarine measurements, may not necessarily be true for the Arctic Ocean as a whole and an alternative hypothesis that sea-ice thickness distribution changed in response to the AO but that sea-ice volume may not have changed needs to be carefully evaluated.

Scientific debate continues as to the cause of the areal shrinkage of the arctic sea ice. There is some support for the idea that it is probably part of a natural fluctuation in polar climate[13], while others claim it is another indication of the response to global warming due to increased levels of greenhouse gases (GHGs)[14].

Length of melt season (9.2.2.4)

Smith D.[15] used satellite data, predominantly from the Beaufort Sea, to estimate that the melt season increased by about 5.3 days per decade during 1979 to 1996. Rigor et al.[16] found an increase of about 2.6 days per decade in the length of the melt season in the eastern Arctic but a shortening in the western Arctic of about 0.4 days per decade. These trends parallel general observations of a 1° C per decade increase in air temperature in the eastern Arctic compared to a 1° C per decade decrease in the western Arctic for the same time period[17].

Sea-ice drift (9.2.2.5)

Fig. 9.3. Sea-ice drift patterns for years with (a) pronounced AO- (anticyclonic) conditions and (b) pronounced AO+ (cyclonic) conditions[18]. The small arrows show the detailed ice drift trajectories based on an analysis of sea level pressure[19]. The large arrows show the general ice drift patterns.

General sea-ice motion in the Arctic Ocean is organized by the Transpolar Drift in the Eurasian Basin and by the Beaufort Gyre in Canada Basin (Fig. 9.1). Although it has long been recognized that large-scale ice-drift patterns in the Arctic undergo interannual changes, it was not until the International Arctic Buoy Programme (IABP) that sufficient data became available to map the ice drift in detail and thereby directly link changes in sea-ice trajectories to the AO. The IABP data from 1979 to 1998 suggest two characteristic modes of arctic sea-ice motion (Fig. 9.3), one during a low AO index (AO-) and the other during a high AO index (AO+)[20]. The ice motion revealed by drifting buoys released onto the ice is reasonably well simulated by models[21]. There are two principal differences between the two modes. First, during pronounced AO- conditions (Fig. 9.3a), sea ice in the Transpolar Drift tends to move directly from the Laptev Sea across the Eurasian Basin and out into the Greenland Sea, whereas during pronounced AO+ conditions (Fig. 9.3b), ice in the Transpolar Drift takes a cyclonic diversion across the Lomonosov Ridge and into Canada Basin[22]. Second, during pronounced AO+ conditions (Fig. 9.3b), the Beaufort Gyre shrinks back into the Beaufort Sea and becomes more disconnected from the rest of the Arctic Ocean, exporting less sea ice to the East Siberian Sea and importing little sea ice from the region to the north of the Canadian Archipelago that contains the Arctic’s thickest multi-year ice[23]. These changes in sea-ice drift are principally due to the different wind patterns associated with the two AO modes.

During AO- conditions the East Siberian Sea receives much of its ice from the Beaufort Sea and there is an efficient route to carry ice clockwise around the arctic margin of the East Siberian Sea and out toward Fram Strait. Under the strong AO+ conditions of the early 1990s, the Beaufort Sea ice became more isolated whereas sea ice from the Kara, Laptev, and East Siberian Seas was displaced into the central Arctic and toward the Canadian Archipelago. It is not clear from the IABP data how much sea ice from the Russian shelves might be transported into the Canadian Archipelago or the Beaufort Gyre under AO+ conditions, but models[24] suggest that such transport may be important at times.

Fram Strait is the main gateway for arctic ice export. Satellite data, drifting buoys, numerical models, and budgets have been used to construct estimates of the sea-ice flux through Fram Strait[25]. Widell et al.[26] observed a mean sea-ice thickness of 1.8 m and a monthly mean volume flux of 200 km3 for the period 1990 to 1999. They found no trends in ice thickness and volume flux. The maximum sea-ice volume flux occurred in 1994/95 due to strong winds, combined with relatively thick ice.

Chapter 9: Marine Systems
9.1. Introduction (Sea ice effect on marine systems in the Arctic)
9.2. Physical oceanography
9.2.1. General features (Sea ice effect on marine systems in the Arctic)
9.2.2. Sea ice
9.2.3. Ocean processes of climatic importance
9.2.4. Variability in hydrographic properties and currents
9.2.5. Anticipated changes in physical conditions
9.3. Biota
9.3.1. General description of the Arctic biota community
9.3.2. Physical factors mediating ecological change
9.3.3. Past variability – interannual to decadal
9.3.4. Future change – processes and impacts on biota
9.4. Effects of changes in ultraviolet radiation
9.5. The carbon cycle and climate change
9.6. Key findings (Sea ice effect on marine systems in the Arctic)
9.7. Gaps in knowledge and research needs

References


Citation

Committee, I. (2012). Sea ice effect on marine systems in the Arctic. Retrieved from http://editors.eol.org/eoearth/wiki/Sea_ice_effect_on_marine_systems_in_the_Arctic
  1. ↑ Parkinson, C.L., D.J. Cavalieri, P. Gloersen, H.J. Zwally and J.C. Comiso, 1999. Arctic sea ice extents, areas, and trends, 1978–1996. Journal of Geophysical Research, 104(C9):20837–20856.
  2. ↑ Gloersen, P., 1995. Modulation of hemispheric sea-ice cover by ENSO events. Nature, 373:503–506.–Mysak, L.A. and D.K. Manak, 1989. Arctic sea-ice extent and anomalies, 1953–1984. Atmosphere-Ocean, 27(2):376–405.–Polyakov, I.V., G.V. Alekseev, R.V. Bekryaev, U.S. Bhatt, R. Colony, M.A. Johnson, V.P. Karklin, D.Walsh and A.V.Yulin, 2003. Long-term ice variability in Arctic marginal seas, Journal of Climate, 16(12):2078–2085.–Rigor, I.G., J.M. Wallace and R.L. Colony, 2002. Response of sea ice to the Arctic Oscillation. Journal of Climate, 15:2648–2663.–Zakharov, V.F., 1994. On the character of cause and effect relationships between sea ice and thermal conditions of the atmosphere. Berichte zur Polarforschung, 144:33–43.
  3. ↑ Wadhams, P., 2000. Ice in the Ocean. Gordon and Breach Science Publishers, Amsterdam, 351pp.
  4. ↑ Wadhams, P., 2000. Ice in the Ocean. Gordon and Breach Science Publishers, Amsterdam, 351pp.
  5. ↑ Wadhams, P., 2000. Ice in the Ocean. Gordon and Breach Science Publishers, Amsterdam, 351pp.
  6. ↑ Johannessen, O.M. and M. Miles, 2000. Arctic sea ice and climate change – will the ice disappear in this century? Science Progress, 83(3):209–222.
  7. ↑ Wadhams, P., 2000. Ice in the Ocean. Gordon and Breach Science Publishers, Amsterdam, 351pp.
  8. ↑ AMAP, 1998. The AMAP Assessment Report: Arctic Pollution Issues. Arctic Monitoring and Assessment Programme, Oslo, xii+859pp.
  9. ↑ Cavalieri, D.J., P. Gloersen, C.L. Parkinson, J.C. Comiso and H.J. Zwally, 1997. Observed hemispheric asymmetry in global sea ice changes. Science, 278:1104–1106.
  10. ↑ Johannessen, O.M., E.V. Shalina and M.W. Miles, 1999. Satellite evidence for an Arctic sea ice cover in transformation. Science, 286:1937–1939.
  11. ↑ Rothrock, D.A., Y. Yu and G.A. Maykut, 1999. Thinning of the Arctic sea-ice cover. Geophysical Research Letters, 26(23):3469–3472.
  12. ↑ Holloway, G. and T. Sou, 2002. Has Arctic sea ice rapidly thinned? Journal of Climate, 15:1691–1701.–Polyakov, I.V. and M.A. Johnson, 2000. Arctic decadal and interdecadal variability. Geophysical Research Letters, 27(24):4097–4100.
  13. ↑ Rothrock, D.A., Y. Yu and G.A. Maykut, 1999. Thinning of the Arctic sea-ice cover. Geophysical Research Letters, 26(23):3469–3472.
  14. ↑ Vinnikov, K.Y., A. Robock, R.J. Stouffer, J.E. Walsh, C.L. Parkinson, D.J. Cavalieri, J.F.B. Mitchell, D. Garrett and V.F. Zakharov, 1999. Global warming and Northern Hemisphere sea ice extent. Science, 286(5446):1934–1937.
  15. ↑ Smith, D.M., 1998. Recent increase in the length of the melt season of perennial Arctic sea ice. Geophysical Research Letters, 25(5):655–658.
  16. ↑ Rigor, I.G., R.L. Colony and S. Martin, 2000. Variations in surface air temperature observations in the Arctic, 1979–97. Journal of Climate, 13:896–914.
  17. ↑ Rigor, I.G., R.L. Colony and S. Martin, 2000. Variations in surface air temperature observations in the Arctic, 1979–97. Journal of Climate, 13:896–914.
  18. ↑ Maslowski, W., B. Newton, P. Schlosser, A. Semtner and D. Martinson, 2000. Modelling recent climate variability in the Arctic Ocean. Geophysical Research Letters, 27(22):3743–3746.–Polyakov, I.V. and M.A. Johnson, 2000. Arctic decadal and interdecadal variability. Geophysical Research Letters, 27(24):4097–4100.–Rigor, I.G., J.M. Wallace and R.L. Colony, 2002. Response of sea ice to the Arctic Oscillation. Journal of Climate, 15:2648–2663.
  19. ↑ Rigor, I.G., J.M. Wallace and R.L. Colony, 2002. Response of sea ice to the Arctic Oscillation. Journal of Climate, 15:2648–2663.
  20. ↑ Macdonald, R.W., T. Harner, J. Fyfe, H. Loeng and T. Weingartner, 2003a. The Influence of Global Change on Contaminant Pathways to, within, and from the Arctic. Arctic Monitoring and Assessment Programme, Oslo, xii+65pp.–Rigor, I.G., J.M. Wallace and R.L. Colony, 2002. Response of sea ice to the Arctic Oscillation. Journal of Climate, 15:2648–2663.
  21. ↑ Maslowski, W., B. Newton, P. Schlosser, A. Semtner and D. Martinson, 2000. Modelling recent climate variability in the Arctic Ocean. Geophysical Research Letters, 27(22):3743–3746.–Polyakov, I.V. and M.A. Johnson, 2000. Arctic decadal and interdecadal variability. Geophysical Research Letters, 27(24):4097–4100.
  22. ↑ Mysak, L.A., 2001. Patterns of Arctic circulation. Science, 293:1269–1270.
  23. ↑ Bourke, R.H. and R.P. Garrett, 1987. Sea ice thickness distribution in the Arctic Ocean. Cold Regions Science and Technology, 13:259–280.
  24. ↑ Maslowski, W., B. Newton, P. Schlosser, A. Semtner and D. Martinson, 2000. Modelling recent climate variability in the Arctic Ocean. Geophysical Research Letters, 27(22):3743–3746.–Polyakov, I.V. and M.A. Johnson, 2000. Arctic decadal and interdecadal variability. Geophysical Research Letters, 27(24):4097–4100.
  25. ↑ Kwok, R., and D.A. Rothrock, 1999. Variability of Fram Strait ice flux and North Atlantic Oscillation, Journal of Geophysical Research, 104(C3):5177–5189.–Vinje, T., N. Nordlund and Å. Kvambekk, 1998. Monitoring ice thickness in Fram Strait, Journal of Geophysical Research, 103(C5):10437–10449.
  26. ↑ Widell, K., S. Østerhus and T. Gammelsrød. 2003. Sea ice velocity in the Fram Strait monitored by moored instruments. Geophysical Research Letters, 30(19):1982, doi:10.1029/2003GL018119.
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