Fast Ice Formation Research Articles

Behaviour of ringed seals tagged with satellite transmitters in the North Water polynya during fast-ice formation

Behaviour of ringed seals tagged with satellite transmitters in the North Water polynya during fast-ice formation

Diet of the ringed seal (<i>Phoca hispida</i>) in Greenland

Analysis of 454 stomachs of ringed seals (Phoca hispida) collected from the Inuit hunt in six municipalities in West Greenland and 30 alimentary tracts collected by scientists in East Greenland, showed seasonal and regional differences in the diet. In Northwest and East Greenland polar cod (Boreogadus saida) and Arctic cod (Arctogadus glacialis) were the most dominant prey items. In contrast, seals in central West Greenland mainly preyed upon amphipods (Parathemisto spp.), capelin (Mallotus villosus), redfish (Sebastes sp.) and squid (Gonatus sp.), while capelin was the most important prey item in Southwest Greenland. The material from Uummannaq demonstrates seasonal variations, as euphausiids were common in spring, and snailfish (Liparis spp.) dominated from October through January, where after snailfish disappeared with the formation of fast ice. No age related differences in the diet were found in stomach samples from Avanersuaq, but in Upemavik crustaceans were more abundant in stomach samples from younger immature seals. Greenland halibut (Reinhardtius hippoglossoides) was only present in samples from seals older than 4 years. In Upemavik Arctic cod was the dominant prey item for seals caught in May at the iceedge, whereas polar cod dominated the samples from seals caught in open water.

Seasonal and interannual variations of the oceanic heat flux under a landfast Antarctic sea ice cover

A multilayer thermodynamic model is used to simulate sea ice growth for 12 years between 1958 and 1986 in the vicinity of the Australian station Mawson on the coast of East Antarctica. The atmospheric forcing data for the model are derived from radiosonde profiles and from surface measurements. Global radiation data are available for 4 years, and we use these measurements for comparison with the results of a Zillman‐type model for global radiation. Combining the thermodynamic model with sea ice thickness measurements for 12 years, we solve the energy balance equation for the oceanic heat flux. The oceanic heat flux is not constant but changes with time within the year and from year to year. The oceanic heat flux averages 7.9 W/m2, and the yearly means vary between 5 and 12 W/m2. Seasonal values of the oceanic heat flux range from 0 to 18 W/m2. From the yearly averaged values a decadal trend is evident: During the first years that were analyzed the yearly average lies well above 10 W/m2; then in the mid‐1970s a decrease to 9 W/m2 occurs, while for all later years the values are ∼6–8 W/m2. In general, the oceanic heat flux increases from the start of the fast ice formation season in early April until it breaks out in December or January. To compare the calculated oceanic heat fluxes for different years, we divide the total ice season into three characteristic time regimes of the sea ice growth and calculate the averaged oceanic heat fluxes for each regime. For the first regime (through August) the mean flux is 2.7 W/m2, for the middle regime (September) it is 8.4 W/m2, and for the final regime (October–January) it is 17 W/m2. We discuss the results of our model calculations in conjunction with current meter observations, which give evidence of seasonally varying intrusions of relatively warm Circumpolar Deep Water into Prydz Bay. Comparison of passive microwave data of sea ice extent and concentration (from the scanning multichannel microwave radiometer sensor) with the model results reveals a correlation between the magnitude of the oceanic heat flux and local features such as polynyas.

Current climatic changes and their impact on the ice regime of the arctic seas

Abstract The author utilizes ice data from Arctic stations and from ice reconnaissance flights to investigate the impact of the cooling trend that began in the early 1940's on sea ice conditions in the Soviet Arctic. One striking feature is the pronounced contrast in this impact between the Eastern and Western Arctic, the dividing line lying at about 160°E. Thus while ice formation in the Kara Sea in the fall occurred on average 15–20 days earlier in the decade 1946–55 compared to 1956–65, in the eastern part of the East Siberian Sea ice formation occurred 10–15 days later. The same pattern emerges with regard to ice thicknesses in late winter, date of formation of fast ice in the fall, and ice concentration in late August, i.e., at the height of the navigation season. Quite definitely there has been a significant deterioration in navigation conditions in the Western Arctic and particularly in the Kara Sea; by contrast, navigation conditions have improved markedly in the eastern part of the East Siberian ...