Polar Research (E-Journal)
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Decadal decrease of Antarctic sea ice extent inferred from whaling records revisited on the basis of historical and modern sea ice records
No full textIn previous work, whaling catch positions were used as a proxy record for the position of the Antarctic sea ice edge and mean sea ice extent greater than the present one spanning 2.8° latitude was postulated to have occurred in the pre-1950s period, compared to extents observed since 1973 from microwave satellite imagery. The previous conclusion of an extended northern latitude for ice extent in the earlier epoch applied only to the January (mid-summer) period. For this summer period, however, there are also possible differences between ship and satellite-derived measurements. Our work showed a consistent summer offset (November– December), with the ship-observed ice edge 1 - 1.5° north of the satellitederived ice edge. We further reexamine the use of whale catch as an ice edge proxy where agreement was claimed between the satellite ice edge (1973–1987) and the ship whale catch positions. This examination shows that, while there may be a linear correlation between ice edge position and whale catch data, the slope of the line deviates from unity and the ice edge is also further north in the whale catch data than in the satellite data for most latitudes. We compare the historical (direct) record and modern satellite maps of ice edge position accounting for these differences in ship and satellite observations. This comparison shows that only regional perturbations took place earlier, without significant deviations in the mean ice extents, from the pre-1950s to the post-1970s. This conclusion contradicts that previously stated from the analysis of whale catch data that indicated Antarctic sea ice extent changes were circumpolar rather than regional in nature between the two periods
Variability of the Northern Annular Mode’s signature in winter sea ice concentration
No full textHistorical winter sea ice concentration data are used to examine the relation between the Northern Annular Mode (NAM) and the sea ice concentration in the Nordic seas over the past 50 years. The well known basic response pattern of a seesaw between the Labrador Sea and the Greenland, Iceland and Barents seas is being reproduced. However, the response is not robust in the Greenland and Iceland seas. There the observed variability has a more complex relationship with surface temperatures and winds. We divide the sea ice response into three spectral bands: high (P 15 year) filtered NAM indices. This division is motivated by the expected slow response of the ocean circulation which might play a significant role in the Greenland and Iceland seas. The response to the NAM is also examined separately for the periods before and after 1976 to identify variations due to the relocation of the northern centre of the North Atlantic Oscillation
Northern Hemisphere sea ice simulations by global climate models
No full textThe study described here is a synthesis of global climate model projections of Northern Hemisphere sea ice through the end of the 21st century. The synthesis includes an enhancement of the informational content of the projections from a set of five global atmosphere–ocean–ice models. The adjustments are based on the systematic errors in the models’ present-day simulations relative to the HadISST observational data set. All models show decreases of sea ice through the 21st century when forced by the B2 scenario of greenhouse gas and aerosol concentrations. However, the differences in the present-day ice coverage simulated by the models are sufficiently large that they dominate the across-model variances of the projected ice extents. The adjustments based on the present-day biases remove much of the spread among the projections. The decreases of the adjusted ice extent by the year 2100 range from about 12 % to about 46 %. The percentage decreases are larger in summer than in winter; much of the Arctic Ocean is ice-free at the time of the summer ice minimum by the year 2099
Variability of the ice export through Fram Strait in 1993–98: the winter 1994/95 anomaly
No full textThe origin of the large positive anomaly of the Fram Strait sea ice export which occurred in winter 1994/95 is analysed on the basis of a model simulation of the Arctic sea ice cover over the period 1993–98. The overall intra-annual and interannual variability in the model is in good agreement with observational estimates and the 1994/95 anomaly is well reproduced with an amplitude amounting to half of the mean winter value. Model results suggest that, concomitant to anomalous export velocities, larger than usual ice thickness in the strait contributes to the outstanding amplitude of the anomaly. Analysis on the ice thickness evolution in the strait indicates that the thick ice advected in Fram Strait at the end of the fall of 1994 originates in the anomalous cyclonic wind stress which prevailed during the preceding summer. This anomalous wind stress resulted in persistent convergence of the ice flow against the northern coasts of Canada and Greenland and in the formation of a large thickness anomaly north of Greenland. The anomaly then feeds the Fram Strait ice flow during those following winter months when the local wind forcing in the strait favours ice drift from the north-west. Our results suggest that short-term wind stress variations resulting in local thickness changes to the north of Fram Strait can lead to substantial variability of the Fram Strait ice export
Recent temperature and precipitation increases in West Siberia and their association with the Arctic Oscillation
No full textSurface air temperature and precipitation records for the years 1958-1999 from ten meteorological stations located throughout West Siberia are used to identify climatic trends and determine to what extent these trends are potentially attributable to the Arctic Oscillation (AO). Although recent changes in atmospheric variability are associated with broad Arctic climate change, West Siberia appears particularly susceptible to warming. Furthermore, unlike most of the Arctic, moisture transport in the region is highly variable. The records show that West Siberia is experiencing significant warming and notable increases in precipitation, likely driven, in part, by large-scale Arctic atmospheric variability. Because this region contains a large percentage of the world's peatlands and contributes a significant portion of the total terrestrial freshwater flux to the Arctic Ocean, these recent climatic trends may have globally significant repercussions. The most robust patterns found are strong and prevalent springtime warming, winter precipitation increases, and strong association of non-summer air temperatures with the AO. Warming rates for both spring (0.5-0.8 °C/decade) and annual (0.3-0.5°C/decade) records are statistically significant for nine often stations. On average, the AO is linearly congruent with 96% (winter), 19% (spring), 0% (summer), 67% (autumn) and 53% (annual) of the warming found in this study. Significant trends in precipitation occur most commonly during winter, when four of ten stations exhibit significant increases (4-13 %/decade). The AO may play a lesser role in precipitation variability and is linearly congruent with only 17% (winter), 13% (spring), 12% (summer), 1% (autumn) and 26% (annual) of precipitation trends
Permafrost in Svalbard: a review of research history, climatic background and engineering challenges
No full textThis paper reviews permafrost in High Arctic Svalbard, including past and current research, climatic background, how permafrost is affected by climatic change, typical permafrost landforms and how changes in Svalbard permafrost may impact natural and human systems. Information on active layer dynamics, permafrost and ground ice characteristics and selected periglacial features is summarized from the recent literature and from unpublished data by the authors. Permafrost thickness ranges from less than 100 m near the coasts to more than 500 m in the highlands. Ground ice is present as rock glaciers, as ice-cored moraines, buried glacial ice, and in pingos and ice wedges in major valleys. Engineering problems of thaw-settlement and frost-heave are described, and the implications for road design and construction in Svalbard permafrost areas are discussed
Numerical modelling of the Storfjorden (Svalbard) polynya development due to wind stress: role of the sea ice rheology and damping forces
No full textRemote sensing of the ice cover in Storfjorden (Svalbard) revealed the persistence and evolution of latent heat polynyas during the winter of 1997/98. Latent heat polynyas open mechanically under wind stress or ocean currents that transport the ice cover away. In the present work we used mathematical modelling to simulate the Storfjorden polynya size and geometry caused by wind stress, measured at the meteorological station on the island of Hopen in winter 1997/98. The dependence of the polynya outlines on the wind velocity is presented. Two approaches were used: quasi-static and dynamic. Quasi-static simulations are based on a time-independent, linear ice stress-strain relationship valid for the low strain rates only. Time dependence of the ice cover fracture is joined with stress-strain nonlinearity caused by ice delayed-elastic recovery and viscosity. Results are compared to satellite observations from the synthetic aperture radar (SAR) of ERS-2. The simulation results show that a northern wind opens a larger polynya (ca. 30%) than does a north-eastern wind with the same speed. The results also indicate that the bathymetry and geometry of the fjord might have a stronger influence on the polynya opening and development than the location of individual islands and reefs
The reproductive features of a mature female of the deep sea planktonic squid Galiteuthis glacialis (Cephalopoda: Cranchiidae) from the Southern Ocean
No full textA mature female Galiteuthis glacialis (430 mm mantle length) was caught south of the Falkland Islands (53°S, 58°W) at a depth of 976-1001 m over a bottom depth of 1582-2378 m. A total of 8 spermatangia (15-19 mm in length) were found inserted into the mantle wall, which was of gelatinous consistency. Its ovary contained 3 605±42 oocytes, mostly 2.2-2.5 mm in length, and there were 21 ripe eggs (3.0-3.2±2.2-2.7 mm) in the oviducts. Only one resorpting oocyte (1.4 mm) was found. This is the only description of a mature female of this species, though two spent females have been previously described and three more mentioned by other authors
Twenty of the most thermophilous vascular plant species in Svalbard and their conservation state
No full textAn aim for conservation in Norway is preserving the Svalbard archipelago as one of the least disturbed areas in the Arctic. Information on local distribution, population sizes and ecology is summarized for 20 thermophilous vascular plant species. The need for conservation of northern, marginal populations in Svalbard is reviewed, using World Conservation Union categories and criteria at a regional scale. Thirteen species reach their northernmost distribution in Svalbard, the remaining seven in the western Arctic. Nine species have 1-8 populations in Svalbard and are assigned to Red List categories endangered or critically endangered: Campanula rotundifolia, Euphrasia frigida, Juncus castaneus, Kobresia simpliciuscula, Rubus chamaemorus, Alchemilla glomerulans, Ranunculus wilanderi, Salix lanata and Vaccinium uliginosum, the last four species needing immediate protective measures. Five species are classified as vulnerable: Betula nana, Carex marina ssp. pseudolagopina, Luzula wahlenbergii, Ranunculus arcticus and Ranunculus pallasii. Six species are considered at lower risk: Calamagrostis stricta, Empetrum nigrum ssp. hermaphroditum, Hippuris vulgaris (only occurring on Bjørnøya), Juncus triglumis, Ranunculus lapponicus and Rhodiola rosea. The warmer Inner Arctic Fjord Zone of Spitsbergen supports most of the 20 target species and is of particular importance for conservation. Endangered or vulnerable species were found in a variety of edaphic conditions; thus, several kinds of habitats need protection
Review of Islands of the Arctic, by Julian Dowdeswell & Michael Hambrey
No full textThis is a well illustrated introductory book about the islands of the Arctic