Brief communication "Important role of the mid-tropospheric atmospheric circulation in the recent surface melt increase over the Greenland ice sheet"
Open Access
- 7 February 2013
- journal article
- research article
- Published by Copernicus GmbH in The Cryosphere
- Vol. 7 (1), 241-248
- https://doi.org/10.5194/tc-7-241-2013
Abstract
Since 2007, there has been a series of surface melt records over the Greenland ice sheet (GrIS), continuing the trend towards increased melt observed since the end of the 1990's. The last two decades are characterized by an increase of negative phases of the North Atlantic Oscillation (NAO) favouring warmer and drier summers than normal over GrIS. In this context, we use a circulation type classification based on daily 500 hPa geopotential height to evaluate the role of atmospheric dynamics in this surface melt acceleration for the last two decades. Due to the lack of direct observations, the interannual melt variability is gauged here by the summer (June–July–August) mean temperature from reanalyses at 700 hPa over Greenland; analogous atmospheric circulations in the past show that ~70% of the 1993–2012 warming at 700 hPa over Greenland has been driven by changes in the atmospheric flow frequencies. Indeed, the occurrence of anticyclones centred over the GrIS at the surface and at 500 hPa has doubled since the end of 1990's, which induces more frequent southerly warm air advection along the western Greenland coast and over the neighbouring Canadian Arctic Archipelago (CAA). These changes in the NAO modes explain also why no significant warming has been observed these last summers over Svalbard, where northerly atmospheric flows are twice as frequent as before. Therefore, the recent warmer summers over GrIS and CAA cannot be considered as a long-term climate warming but are more a consequence of NAO variability affecting atmospheric heat transport. Although no global model from the CMIP5 database projects subsequent significant changes in NAO through this century, we cannot exclude the possibility that the observed NAO changes are due to global warming.Keywords
This publication has 41 references indexed in Scilit:
- Current and future atmospheric circulation at 500 hPa over Greenland simulated by the CMIP3 and CMIP5 global modelsClimate Dynamics, 2012
- Greenland ice sheet albedo feedback: thermodynamics and atmospheric driversThe Cryosphere, 2012
- Estimating Greenland ice sheet surface mass balance contribution to future sea level rise using the regional atmospheric climate model MARPublished by Copernicus GmbH ,2012
- Recent melt rates of Canadian arctic ice caps are the highest in four millenniaGlobal and Planetary Change, 2012
- Melting trends over the Greenland ice sheet (1958–2009) from spaceborne microwave data and regional climate modelsThe Cryosphere, 2011
- The 1958–2009 Greenland ice sheet surface melt and the mid-tropospheric atmospheric circulationClimate Dynamics, 2010
- Accelerated decline in the Arctic sea ice coverGeophysical Research Letters, 2008
- Reconstruction of the 1979–2006 Greenland ice sheet surface mass balance using the regional climate model MARThe Cryosphere, 2007
- The 1988–2003 Greenland ice sheet melt extent using passive microwave satellite data and a regional climate modelClimate Dynamics, 2006
- Global Warming and the Greenland Ice SheetClimatic Change, 2004