Vegetation type is an important predictor of the arctic summer land surface energy budget

Despite the importance of high-latitude surface energy budgets (SEBs) for land-climate interactions in the rapidly changing Arctic, uncertainties in their prediction persist. Here, we harmonize SEB observations across a network of vegetated and glaciated sites at circumpolar scale (1994-2021). Our variance-partitioning analysis identifies vegetation type as an important predictor for SEB-components during Arctic summer (June-August), compared to other SEB-drivers including climate, latitude and permafrost characteristics. Differences among vegetation types can be of similar magnitude as between vegetation and glacier surfaces and are especially high for summer sensible and latent heat fluxes. The timing of SEB-flux summer-regimes (when daily mean values exceed 0 Wm(-2)) relative to snow-free and -onset dates varies substantially depending on vegetation type, implying vegetation controls on snow-cover and SEB-flux seasonality. Our results indicate complex shifts in surface energy fluxes with land-cover transitions and a lengthening summer season, and highlight the potential for improving future Earth system models via a refined representation of Arctic vegetation types.An international team of researchers finds high potential for improving climate projections by a more comprehensive treatment of largely ignored Arctic vegetation types, underscoring the importance of Arctic energy exchange measuring stations.Peer reviewe

Vegetation type is an important predictor of the arctic summer land surface energy budget

Despite the importance of high-latitude surface energy budgets (SEBs) for land-climate interactions in the rapidly changing Arctic, uncertainties in their prediction persist. Here, we harmonize SEB observations across a network of vegetated and glaciated sites at circumpolar scale (1994–2021). Our variance-partitioning analysis identifies vegetation type as an important predictor for SEB-components during Arctic summer (June-August), compared to other SEB-drivers including climate, latitude and permafrost characteristics. Differences among vegetation types can be of similar magnitude as between vegetation and glacier surfaces and are especially high for summer sensible and latent heat fluxes. The timing of SEB-flux summer-regimes (when daily mean values exceed 0 Wm−2) relative to snow-free and -onset dates varies substantially depending on vegetation type, implying vegetation controls on snow-cover and SEB-flux seasonality. Our results indicate complex shifts in surface energy fluxes with land-cover transitions and a lengthening summer season, and highlight the potential for improving future Earth system models via a refined representation of Arctic vegetation types

Annual course of the atmospheric pressure on the Antarctic

W artykule przedstawiono zmienność przestrzenną przebiegu rocznego ciśnienia atmosferycznego na Antarktydzie. Stwierdzono dwa typy przebiegów rocznych ciśnienia. Na wybrzeżu występuje przebieg charaktery-zujący się półroczną oscylacją, z maksymalnymi wartościami w sezonie letnim i zimowym oraz najniższymi w przejścio-wych porach roku. We wnętrzu kontynentu najwyższe ciśnienie występuje latem, a najniższe w chłodnej połowie roku. Największe amplitudy roczne ciśnienia występują we wnętrzu kontynentu. W ostatnich dwóch dekadach XX wieku zaznaczyły się istotne zmiany w przebiegu rocznym ciśnienia atmosferycznego.At the polar latitudes of the Southern Hemisphere a circulation cell functions which is connected with the strong baric wedge feature of the atmosphere occurring between the Antarctic anticyclone and a very deep circumpolar trough by the Antarctic coastline. The circulation system in the Antarctic region shows seasonal variability called Southern Annular Mode (SAM). In the cold season the tropospheric exchange of air masses strengthens due to the increase of the katabatic winds? speed. The relocation of air masses from over Antarctica to its peripheries has an influence on the annual course of the atmospheric pressure. In the elaboration mean monthly air pressure values were taken into account from 106 Antarctic stations from the beginning of measurements to 2000. On the basis of these data the mean annual course of the atmospheric pressure has been counted as well as the yearly pressure range. Annual courses from two periods: 1958-1980 and 1981-2000 were also compared. Over the Antarctic the annual course of the atmospheric pressure is complex. At the costal part of the continent there are two maxima (in summer and in winter) and two minima in the transient seasons. This course is called semi-annual oscillation (SAO) in the literature. However this phenomenon shows certain regional specifics. On the Antarctic Peninsula and South Orkney Islands the winter maximum is more distinct, while minima are shifted to February and November. In the inland the winter maximum decreases with the distance from the coast and at stations situated in the highest parts of the glacial plateau the highest pressure values occur in summer and distinctly lower ones in winter. At some inland stations a slight increase of the pressure can be observed in the middle of winter what refers to the thermal coreless winters occurring frequently in this region. The annual range of the atmospheric pressure decreases from the coast (15-7 hPa) to the interior of the continent, where it reaches values above 20 hPa. During the last two decades of the 20th century significant changes took place in the annual courses of the pressure in comparison to the years 1958-1980. On the South Orkney Islands and the Antarctic Peninsula the pressure increased in summer and in autumn, while in winter distinctly decreased. At the remaining part of the Antarctic coast pressure decrease occurred in every seasons, and in the Weddell Sea region the autumn and spring minimum significantly deepened. At the majority of the stations the annual amplitudes of the atmospheric pressure decreased after 1980. These changes contributed to the disturbances in the functioning of the Antarctic climate system. On the Antarctic Peninsula the air temperature increased, while at many stations in the Eastern Antarctic considerable cooling occurred

Change of air temperature range on the Antarctic in the years 1958-2000

The progressive increase in the concentration of greenhouse gases in the atmosphere in consequence leads to the rise of the global air temperature. According to the III Report of IPCC (2001) from 1880 the mean temperature on the Earth has grown by 0.6°C ą0.2°C. The reaction of polar regions to the greenhouse effect is unknown. The Antarctic climate shows a considerably greater variability in comparison with the lower latitudes of the Southern Hemisphere. This is conditioned by interactions between the atmospheric circulation, the ocean, and the cryosphere. According to the scenarios of global greenhouse effect the temperature at the polar regions should grow by 3°C in summer and 4-5°C in winter. However, these model researches are not confirmed in reality. This shows that our knowledge concerning the functioning of climate system of the polar regions is insufficient. In the paper we have used monthly mean air temperature values for 21 stations being in operation on the Antarctic in the years 1958-2000 and for 34 stations making observations in the years 1981-2000. After checking the homogeneity of the series by the Alexandersson?s (1986) test we have counted the trends of air temperature. The average trend for annual and seasonal values were expressed by temperature change per 10 years. In the years 1958-2000 on the Antarctic the trend of the mean annual values of the air temperature shows great spatial differentiation. These differences are connected with the radiation balance depending on the variability of cloudiness and the albedo of the surface, and on the transformation of pressure fields and changes of the atmospheric circulation. Statistically significant (on 0.95 significance level) air temperature increase occurred on the western coast of the Antarctic Peninsula (for example Faraday 0.67°C/10 years) and at the stations Belgrano and McMurdo. A negative air temperature trend occurred on the South Pole (-0.21°C/10 years) and on the Droning Maud Land. The temperature changes in the region of the Antarctic Peninsula are correlated with the extension and surface of sea ice, especially in winter. There are considerable differences of air temperature trends on the Antarctic between the periods 1958-1980 and 1981-2000. The period 1958-1980 is characterized by an increase of air temperature, especially on the shore of continent (Casey 0.84°C/10 years, Faraday 0.76°C/10 years, Halley 0.69°C/10 years). The interior of the continent is distinguished by stability of weather conditions. Year-to-year temperature changes are smaller, then at the coast (the trend at the Amundsen-Scott station average 0.26°C/10 years). During the last years (1981-2000) significant changes took place in the tendency of air temperature on the Antarctic. In many regions of the Antarctic cooling began, on the cost of East Antarctica the temperature decreases, on the coasts of the Wilkes Land (Casey -0.82°C/10 years) and the Weddell Sea (Halley -1.13?C/10 years, Larsen Ice -0.89°C/10 years), especially in the autumn-winter period. In the interior of the continent also lower and lower temperatures occurred (Amundsen-Scott -0.42°C/10 years, Dome C -0.71°C/10 years). The cooling can be observed in all seasons, but it is the greatest in summer and autumn, when the decrease of solar radiation was observed in connection with the growing cloudiness. Vostok situated at the highest parts of ice dome does not show statistically significant trend. An increase of the temperature was observed in the interior of West Antarctica (Byrd 0.37°C/10 years). The warming rate of the climate became weaker on the Antarctic Peninsula (Faraday 0.56°C/10 years). The largest temperature changes occurred in the autumn-winter season when in the Antarctic Peninsula region the temperature increased, while in the interior and at the coast of East Antarctica considerably fell. Climate changes during the last 20 years of the 20th century showed the weakening of the warming rate on the Antarctic Peninsula and distinct cooling on the East Antarctica. The lack of warming, or even cooling, on the East Antarctica, is favourable to maintain the present climate system in this region. The increasing air temperature on the West Antarctic, especially on the Antarctic Peninsula caused many natural consequences. The ablation of glaciers clearly intensified, deglaciation takes place, glaciers retreat. The environmental changes lead to disturbances in the functioning of the Antarctic ecosystem

Annual course of air temperature on the Antarctic

On the Antarctic the annual course of air temperature shows a considerable spatial differentiation. Over the inland the course of temperature during the year is conditioned by insolation-radiational factors. On the coast the role of circulation factors connected with the advection of air masses from above the ocean or from the interior of the continent. In the paper mean monthly air temperatures from 56 stations making standard meteorological observations and from 38 automatic weather stations (AWS) have been used. On the Antarctic there types of annual air temperature courses can be distinguished: Oceanic - characterised by positive air temperatures in the summer season with the highest temperatures in February and by mild temperatures in the winter months (to -10°C). As a result of the ocean influence spring is considerable colder then autumn. The annual amplitudes are small (to 10-15°C). This type occurs on the western coast of the Antarctic Peninsula and on the subantarctic islands. Continental - with very low air temperatures. The warmest month is December with temperatures below -30°C in the interior of the continent. In winter the lowest mean monthly temperatures reach -70°C. The temperature frequently increases in the middle of winter; this phenomenon is called kernlose winter. The annual amplitude of air temperature is not high and in the interior its value reaches 30-35°C. The continental type includes the whole Antarctic except the narrow coastal belt. Coastal - characterised by air temperature around 0°C in the summer period. The warmest month is January. The lowest temperatures occur in January (-30° do -40°C). The growth of temperature in spring delays the heat uptake for the melting of sea ice. The annual amplitude of the air temperature is quite high and exceeds 20°C. Due to the influence of circulation factors on the Antarctic the annual course of the air temperature shows a large variability from year to year