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At
the moment I am looking through some very detailed maps and a
climate atlas especially of the 1002 area. This will aid me in
understanding patterns of the climate that influence flora and fauna in
the relevent area. Eventually it may lead us to define the parameters
for assessing the well-being of the ecosystem. Further research: As
I started working on the climatic portion of the ecosystem, I realised
that the effects of global warming on these ecosystems cannot be
neglected. Climate along the Arctic coast is strongly moderated by the ocean all year round. Marine influence is significantly reduced moving southwards where a more continental climate prevails. In studying the interaction of organisms with their environment, it is important to consider the microclimate. Climate near the ground, however, is largely a function of energy exchange phenomena at the ground-air interface. Seasonal Snow Cover Snow covers the ground for more than 8 months of the year (generally from October through April). The average maximum thickness of the seasonal snow cover varied from about 30 cm along the Arctic coast to about 40 cm inland for the period from 1977 through 1988. (Zhang et al., 1996a) Analyses of data collected by a number of studies done from the late 1940s onwards at and around Barrow and Prudoe Bay showed that the permafrost surface has warmed 2 to 4 degrees Centigrade in the Alaskan Arctic over the last century. (Lachenbruch and Marshall 1986; Lachenbruch et al., 1988) Snow has high reflectivity and emissivity which cool the snow surface, while snow cover is a good insulater which insulates the ground. Melting snow is also a heat sink owing to its high latent heat of fusion. These thermal properites of snow introduce competing effects with air temperature on the ground thermal regime. (Zhang et al., 1997). In spite of the high albedo from spring and early summer snow and cloud cover, net radiation is positive throughout the year. (Hare, F. K. 1972) The thickness of the seasonal snow cover can vary substantially on a micro scale owing to the impact of wind, ground surface morphology and vegetation. Along the coast, the ground surface is relatively flat and is mainly occupied by low-centre polygons. Vegetation is poorly developed. The coastal regions also experience high wind speeds during the winter months. (Haugen, 1982). In this setting the snow can be either blown away or well packed by strong wind; hence the insulating effect is reduced. Inland, the ground surface becomes rough and vegetation changes significantly as a result of increased summer warmth. Wind redistributes the snow which is better trapped in the troughs and depressions created by rough micro relief and the taller vegetation. Hence, the trapped snow increases the insulating effect of the seasonal snow cover. This in turn influences the permafrost conditions which determine the kind of vegetation in the area. On a monthly basis, seasonal snow cover warms the ground surface during winter months but cools it during the period of snowmelt. On an annual basis the seasonal snow cover definately warms the ground surface. (Zhang et al., 1997) In contrast, the Arctic inland and Arctic foothills feature lower wind speed, a very rough surface with tussocks, troughs and depressions, and well-developed vegetation. Snow can be inturrupted and trapped by vegetaion and rough surface, increasing the insulating effect and permafrost temperatures. Unlike the varying ground temperatures, the mean annual air temperature was nearly constant at about -12.4 with a variation of about 0.4 degrees Centigrade, within about 120 km from the Arctic coast. Snow and shrubs form a positive feedback loop that could change land surface processes in the Arctic. The increased subnivian soil temperatues that are observed would produce conditions favourable to shrub growth (i.e. more decomposition and nutrient mineralization). (Strum et al., 2001) Aerial photographs taken of Alaska's North Slope during the 1940s offer some of the best evidence of such changes—a dramatic increase in the growth of trees and shrubs in the Arctic. (http://www.uaf.edu/seagrant/NewsMedia/01ASJ/06.01.01shrubs.html) Sources Effects of Climate on the Active Layer and Permafrost on the North Slope of Alasla, U.S.A. T. Zhang, T. E. Osterkamp and K. Stamnes 1997 (Geophysical Institute, University of Alaska, Fairbanks) Climate of Remote Areas in North Central. Alaska 1975-1979, Summary Haugen, R. K. (1982) Permafrost Temperatures and the Changing Climate. Lachenbruch, A. H., Cladouhos, T. T. and Saltus, R. W. (1988) Changing Climate: geothermal evidence from permafrost in the Alaskan Arctic. Science, 234, 689-696 Lachenbruch, A. H. and Marshell, B. V. (1986)Some Characteristics of the Climate in Northern Alaska Zhang, T., Osterkamp, T. E. and Stamnes, K. (1996a) Potential
Impact of a warmer climate on permafrost in Alaska Snow-shrub
interactions in the Arctic tundra: A hypothesis with climatic
implications Arctic
Tundra ecosystems The
Boreal Bioclimates |
| Last updated: Nov 2nd, 2003 | Rabia
Chaudhry |