Influence of sea ice on Arctic precipitation

Abstract

Global climate is influenced by the Arctic hydrologic cycle, which is, in part, regulated by sea ice through its control on evaporation and precipitation. However, the quantitative link between precipitation and sea ice extent is poorly constrained. Here we present observational evidence for the response of precipitation to sea ice reduction and assess the sensitivity of the response. Changes in the proportion of moisture sourced from the Arctic with sea ice change in the Canadian Arctic and Greenland Sea regions over the past two decades are inferred from annually averaged deuterium excess (d-excess) measurements from six sites. Other influences on the Arctic hydrologic cycle, such as the strength of meridional transport, are assessed using the North Atlantic Oscillation index. We find that the independent, direct effect of sea ice on the increase of the percentage of Arctic sourced moisture (or Arctic moisture proportion, AMP) is 18.2 ± 4.6% and 10.8 ± 3.6%/100,000 km(2) sea ice lost for each region, respectively, corresponding to increases of 10.9 ± 2.8% and 2.7 ± 1.1%/1 °C of warming in the vapor source regions. The moisture source changes likely result in increases of precipitation and changes in energy balance, creating significant uncertainty for climate predictions.

Keywords: climate change; deuterium excess; precipitation; sea ice; water cycle.

Fig. 1.

Location of sites for monthly precipitation isotope ratio measurements. Shown are Canadian Arctic sites Alert, Eureka, and Cambridge Bay, Canada and Greenland Sea sites Reykjavìk, Iceland; Ny-Ålesend, Norway; and Danmarkshavn, Greenland. Local moisture sources Baffin Bay (BB) and Greenland Sea (GS) are labeled as well.

Fig. 2.

(A and B) Leverage plots (43) for multiple regressions of d-excess against local sea ice extent and the NAO index for (A) Canadian Arctic and (B) Greenland Sea regions. Solid circles are observations for individual years and sites with site mean removed. The regressions yield overall r² and P values of 0.39, <0.0001 and 0.33, 0.0006 for A and B, respectively.

Fig. 3.

Leverage plots (43) for multiple regression of Ny-Ålesend (NYA) – Reykjavìk (REY) d-excess difference against Greenland Sea ice extent and the NAO index. The results are r² = 0.64 and P = 0.010.

Fig. 4.

(A and B) Contours of the mean meridional wind speed anomaly at 500 hPa for (A) the five strongest positive (1990, 1992, 1994, 1999, and 2011) and (B) negative (1998, 2005, 2008, 2009, and 2010) NAO years during the study period. Positive (negative) anomaly values represent anomalously high southerly (northerly) wind speeds. The plots show the opposite wind directions in the Greenland Sea and Canadian Arctic regions and the wind reversal with NAO phase. Image provided by the NOAA/ESRL Physical Sciences Division, Boulder, CO, at www.esrl.noaa.gov/psd/; data from ref. .