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Stan termiczny Atlantyku Północnego a zlodzenie mórz Barentsa i Grenlandzkiego (1972-1994)

Styszyńska A.

Problemy Klimatologii Polarnej

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2004

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nr 14

39-57

EN

This work deals with correlations between anomalies in SST (sea surface temperature) in the North Atlantic and the sea ice area of the Barents and Greenland seas. This research made use of mean monthly sea ice cover with density >= 10% observed in the Barents and Greenland seas over the period 1972-1994 (calculated on the bases of weekly area of sea ice cover of the above mentioned seas collected in NCDC data set ?1972-1994 Sea Ice Historical Data Set?). The thermal condition of the North Atlantic is characterised by the values of anomalies in mean monthly sea surface temperature (SST) in so called ?controlled grids? (2° x 2°) selected/appointed here by A.A.Marsz (1999a, 2001). Their location is presented in Fig.1. A standard statistical analysis has been used in this research (correlation analysis, regression analysis). The strongest synchronic correlations (observed in the same months) with the sea ice cover of the said seas have been noted in grids located north of the North Atlantic Current and characterising the following waters (Tables 1 and 2): of the Labrador Sea (located within the range of Labrador Current activity) - [50,52], those north of the Gulfstream delta - [40,52] and those located inside the circle of the cyclonic circulation of the North Atlantic - [30,54]. The highest coefficient values of linear correlation, at a level p<0.05 exceeding the statistical significance, were noted in winter months (December, January, February) and those spring ones (April, May, June) as well as in summer - in July and August (the Greenland Sea). There are also several asynchronic correlations. The results of analysis of multiple regression between the SST anomalies and the area of the sea ice cover indicated that the sea areas in which the changeability in their thermal condition has the greatest influence on the formation of the sea ice cover of the said seas are located in the western part of the North Atlantic.

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Związki bilansu masy lodowców w rejonie Kongsfjordu (NW Spitsbergen) z pokrywą lodową mórz Grenlandzkiego i Barentsa

Styszyńska A.

Problemy Klimatologii Polarnej

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2002

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nr 12

133-146

EN

The sea ice cover of the Greenland and Barents seas is characterised by great seasonal and interannual changeability which has influence on radiation and heat balance of that region. This changeability is directly observed in changes in atmospheric circulation and further noted in changes in meteorological elements (mainly in air temperature, cloudiness, precipitation and wind). Changes in weather conditions determine both the value of losses of glacier masses in a given balance year and the value of ice masses accumulation. This article tries to find the answer to a question if and to what extent the variability of the extent and rate of the Barents and Greenland seas ice formation is directly reflected in changeability of glaciers masses balance in the region of Spitsbergen. This research was based on the mass balance of two small glaciers located in the region of Kongsfjord, i.e. Austre Brogger and Midre Lovén. The mean monthly values of sea ice cover observed in the Greenland and Barents seas in the period 1972-1994 were used in this research (the values calculated on the basis of 1-week values of these seas ice cover taken from NCDC - Asheville). The values of winter, summer and net balances of the said glaciers were drawn from article by Lefauconnier et al. (1999). In addition, the correlation was examined between the balance Austre Brogger and Midre Lovén glaciers and the changeability of atmospheric circulation described by Niedźwiedź ?circulation types? (2001). The research made use of standard statistical analysis (correlation and regression analysis). Statistically significant correlations have been noted between the values of winter balances of both examined glaciers and the size of ice cover of the Barents and Greenland seas at the initial stage of its formation - in November (r ~ -0.55÷0.64, adj. R2 ~ 0.30÷0.35). The result of analysis of multiple regression indicated that the strongest correlation with ice cover of the Greenland Sea occurs in September, whereas in the Barents Sea in December (R ~ 0.70÷0.83). Changes in sea ice cover observed in that time explain 44% and 65% of changeability in winter balance of Austre Brogger and Midre Lovén glaciers, respectively. These results suggest that the process of heat transfer from the ocean to the atmosphere may by very intensive when the sea is merely covered with ice in the areas on the way of main directions of air mass advection. This will provide favourable condition for clear domination of sea air masses resulting in the increase in air temperature (Styszyńska 2000) and precipitation in the region of NW Spitsbergen. The summer balance of the examined glaciers is influenced by the changes in ice conditions only to a small extent. The only significant correlation with sea ice condition of the Greenland Sea was noted in August. Lack of the discussed correlation in summer is attributed to the influence of insolation and radiation factors whose importance increase during the polar day (as indicated in research by Lefauconnier et al. (1999)).

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Zmiany zlodzenia mórz Grenlandzkiego i Barentsa w świetle zmian wskaźnika intensywności Prądu Labradorskiego (1972-1994). Wstępne wyniki analizy

Styszyńska A.

Problemy Klimatologii Polarnej

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2001

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nr 11

93-104

EN

The Barents and Greenland seas are characterised by great seasonal and interannual changeability in the ice cover. Research carried out by many authors prove that the ice regime of these seas is influenced, to a great extent, by large scalę changes in atmospheric circulation and by the ocean surface circulation of the North Atlantic and the Arctic Ocean. Such correlations arę mainly of teleconnection type and show phase shifts (among others Mysak 1995, Deser et. al. 2000). One of the elements of the sea surface circulation of the Atlantic Ocean is the Labrador Current. The intensity of this current changes in time. In the periods when the Labrador Current becomes strong, its waters form vast anomalies in the sea surface temperaturę in the NW Atlantic. Further they spread eastwards along the north edge of the North Atlantic Current and with some delay, have influence on the atmospheric circulation in the central and east part of the North Atlantic (Marsz 1997, 1999). The way how the changes in the intensity of the Labrador Current influence the climate nas not been discovered yet. The intensity of this current can be defined by means of an index (WPL - Labrador Current Intensity lndex) established by Marsz (Internet). This work examines if there is direct correlatton between the changes in the sea-ice cover of the Barents and Greenland seas and the variability of the intensity index of the Labrador Current. The research madę use of homogenous data concerning a week-old sea ice cover observed at the analysed seas and the values of intensity index of the Labrador Current in the period January 1972 until December 1994 given by Marsz (obtained from NIC and NCDC - Asheville). It has been stated that over the examined 23-year period (1972-1994) the mean monthly the sea-ice cover in the Barents Sea indicates to strong correlation with the changes in the value of the intensity index of the Labrador Current (Table 1, Fig. 1). The changes in WPL result in the rhythm of changes in the sea-ice cover of the Greenland Sea only in winter (Table 2, Fig. 2). The occurrence of anomalies in the sea surface temperatures in the region SE of New Foundland seem to have great influence on the later formation (after few or several months) of the sea-ice cover in the Barents Sea (Fig. 1, 3. 4, formula 1-3). Changes in the intensity of Labrador Current in a given year explain 30% up to 50% changeability of the sea-ice cover developing in that sea from January to July in the following year (Table 1, Fig. 3). The area of the sea-ice cover in the Greenland Sea is mainly influenced by the intensity of the Transpolar Drift and East-Greenland Current transporting considerable amount of ice from the Arctic Ocean. Only during fuli winter season, from January to March, the correlation between the intensity of the Labrador Current and the sea-ice cover reaches statistical significance (Table 2). The results of the carried out analysis point to significant influence of advection factor on the sea-ice cover of the examined seas. In both analysed seas the phenomenon is connected to both the character and intensity of the Atlantic waters flow and to greater frequency of occurrence of specified forms of air circulation in the region of central and eastern part of the North Atlantic, possible at a given distribution of anomalies in surface waters of the North Atlantic.