Examination of precipitation variability in southern Greenland

Abstract

The surface mass balance of the Greenland ice sheet has decreased in recent decades with important implications for global sea level rise. Here a climate reanalysis model is used to examine observed circulation variability and changes in precipitation across southern Greenland to gain insight into the future climate in the region. The influence on precipitation from the North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), Icelandic Low, Azores High, regional blocking patterns, and near‐surface temperature and winds are explored. Statistically significant correlations are higher between precipitation and the Icelandic Low and near‐surface winds (0.5–0.7; p < 0.05) than correlations between precipitation and either the NAO or AMO climate indices (southwest Greenland: r = 0.12 and 0.28, respectively; and southeast Greenland: r = 0.25 and −0.07, respectively). Moreover, the recent enhanced warming in the Arctic (Arctic amplification) and the increase in the Greenland Blocking Index coincide with increased mean annual precipitation and interannual variability in southwest Greenland.

Atmospheric River Impacts on Greenland Ice Sheet Surface Mass Balance

“…The glaciological and climatic characteristics of the GrIS exhibit substantial regional variability (Auger et al, ; Langen et al, ; MacGregor et al, ; Mernild et al, ; Poinar et al, ; Van As et al, ; Wilton et al, ), and we reiterate that the recent acceleration in mass loss has been most acute in western Greenland (McMillan et al, ; Mernild et al, ). We further hypothesize based on the results of Liu and Barnes () and M16 that AR moisture transport is often directed into one of two favored pathways to the west or east of Greenland depending on interactions between the North Atlantic storm track and the GrIS topography.…”

“…Atmospheric conditions tightly control both the ablation and accumulation constituents of SMB. The temporal evolution of overall GrIS SMB and the spatial patterns of SMB across the ice sheet therefore vary widely in response to short‐term weather events as well as lower frequency climate variability (Auger et al, ). Previous studies have shown that anomalous GrIS melt episodes during the warm season often occur under slow‐moving high‐pressure regimes known as “Greenland blocks,” with these blocking anticyclones favored during negative NAO conditions and often preceded by extratropical cyclones tracking to the west of Greenland (Ahlstrøm et al, ; Hanna, Jones, et al, ; Lim et al, ; McLeod & Mote, ).…”

Recent precipitation decrease across the western Greenland ice sheet percolation zone

“…Additionally, we measured melt layer thickness in the laboratory following Graeter et al (2018). To calculate accumulation rates at Raven-Dye-2, we use density data from a 119.6 m long firn core collected in 1997 (Bales et al, 2009) and a 19.3 m long core collected from the same location in 2015, which did not include accumulation rate data (Vandecrux et al, 2018). For this location we use the most recent density data for the near surface and the older densities for depths below the 2015 core.…”

“…For each radar trace we calculate statistically significant differences (at α = 0.05) using a two-sample t test with the GreenTrACS accumulation records for each epoch and RCM accumulation rates for each common year. Additionally, we compare our Green-TrACS accumulation rates with an accumulation map kriged from 295 firn cores and 20 coastal weather stations (Bales et al, 2009; hereafter "Bales09"). We perform the same two-sample t test with the reported Bales09 uncertainty of 0.092 m w.e.…”

“…In addition to temperature-precipitation relationships through the Clausius-Clapeyron equation, previous studies have analyzed the dynamic climate controls on Greenland precipitation. Mernild et al (2014), Auger et al (2017), and Lewis et al (2017) have hypothesized that a positive Atlantic Multidecadal Oscillation (AMO) index correlates with rising accumulation rates over most of the GrIS interior since higher sea surface temperatures increase moisture flux over the GrIS and induce greater snowfall. In addition, high-pressure (blocking) systems east of Greenland tend to deflect eastward-moving storms over central Greenland and increase precipitation, whereas blocking directly over Greenland or in Baffin Bay has the potential to decrease accumulation rates over the GrIS by displacing the polar jet stream and corresponding storm tracks equatorward (Auger et al, 2017).…”