Forskning ved Københavns Universitet - Københavns Universitet


Climatic conditions at the Mittivakkat Glacier catchment (1994-2006), Ammassalik Island, SE Greenland, and in a 109-year perspective (1898-2006)

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The present-day climate in the Mittivakkat Glacier catchment (65ºN), Southeast Greenland, is investigated spatiotemporally based on time series (13 years, 1994-2006) and standard synoptic climate data from the meteorological station in Tasiilaq (Ammasslik), covering 109 years (1898-2006). Within the catchment, meteorological conditions are monitored at the coast (Station Coast, 25 m a.s.l.) for the period 1998-2006 and in the glacier area (Station Nunatak, 515 m a.s.l.) for 1994-2006. During this 13-year period, solar radiation shows increasing values, averaging 0.5 W m-2 y-1, at the nunatak and decreasing values, averaging 1.4 W m-2 y-1, at the coast. The mean annual solar radiation at Station Coast is 102 W m-2 y-1, which is about 10% lower than at Station Nunatak, and is probably caused by increasing and higher percentages of dense clouds and sea fog in the coastal area. The mean annual air temperature is increasing by 0.10ºC y-1 at the nunatak and by 0.05ºC y-1 at the coast, extending the thawing periods by about 50 days and 5 days, respectively. A snow-free period of 64 days is observed at the nunatak. The coastal area is highly dominated by air temperature inversion and sea breezes during spring and summer, strongly controlling the lapse rates within the catchments. The glacier area is highly dominated by katabatic fall winds, resulting in an almost total lack of calm periods. The wind speed is highest during winter, with mean average values around 6.0 m s-1, and gusts up to 35.0 m s-1. The total annual precipitation varies from 1,851 mm w.eq. y-1 at the nunatak (solid precipitation: 80%, mixed: 6%, and liquid: 14%) to 1,428 mm w.eq. y-1 at the coast (53%, 31%, and 16%), covering an average positive orographic effect for solid precipitation during winter (113 mm w.eq. 100 m-1) and a negative effect for liquid precipitation during summer (-52 mm w.eq. 100 m-1). Over the last 109 years (1898-2006) precipitation in the catchment has increased about 85 mm w.eq., covering two significant precipitation- rich periods: 1901-1914 (1,560 mm w.eq. y-1) and 1963-1978 (1,563 mm w.eq. y-1). Mean annual air temperature in the catchment has generally increased 0.2°C through the 109-year period, most significantly ~2.7°C within the last 25 years. The warmest 10-year period since 1898 was 1938-1947, showing an annual average of -1.83ºC, while 1997-2006 was the warmest 10- year period within the last 60 years, with an annual average of - 2.10ºC.
TidsskriftGeografisk Tidsskrift
Udgave nummer1
Sider (fra-til)51-72
StatusUdgivet - 2008

ID: 8650703