Coast-to-interior gradient in recent northwest Greenland precipitation trends (1952–2012)

Abstract

The spatial and temporal variability of precipitation on the Greenland ice sheet is an essential component of surface mass balance, which has been declining in recent years with rising temperatures. We present an analysis of precipitation trends in northwest (NW) Greenland (1952–2012) using instrumental (coastal meteorological station) and proxy records (snow pits and ice cores) to characterize the precipitation gradient from the coast to the ice sheet interior. Snow-pit-derived precipitation near the coast (1950–2000) has increased (∼7% decade ^−1 , p < 0.01) whereas there is no significant change observed in interior snow pits. This trend holds for 1981–2012, where calculated precipitation changes decrease in magnitude with increasing distance from the coast: 13% decade ^−1 (2.4 mm water equivalent (w.e.) decade ^−2 ) at coastal Thule air base (AB), 8.6% decade ^−1 (4.7 mm w.e. decade ^−2 ) at the 2Barrel ice core site 150 km from Thule AB, −5.2% decade ^−1 (1.7 mm w.e. decade ^−2 ) at Camp Century located 205 km from Thule AB, and 4.4% decade ^−1 (1.0 mm w.e. decade ^−2 ) at B26 located 500 km from Thule AB. In general, annually averaged precipitation and annually and seasonally averaged mean air temperatures observed at Thule AB follow trends observed in composite coastal Greenland time series, with both notably indicating winter as the fastest warming season in recent periods (1981–2012). Trends (1961–2012) in seasonal precipitation differ, specifically with NW Greenland summer precipitation increasing (∼0.6 mm w.e. decade ^−2 ) in contrast with decreasing summer precipitation in the coastal composite time series (3.8 mm w.e. decade ^−2 ). Differences in precipitation trends between NW Greenland and coastal composite Greenland underscore the heterogeneity in climate influences affecting precipitation. In particular, recent (1981–2012) changes in NW Greenland annual precipitation are likely a response to a weakening North Atlantic oscillation.

Keywords

• Greenland
• climate
• precipitation
• ice sheet
• weather station
• ice core