North Atlantic blocking regulates cold season air temperature variability over Greenland coastal and ice sheet ablation areas
Abstract
Analyses of Greenland surface air temperature (T2m) data from coastal and on-ice weather stations, climate models, and ice core reconstructions indicate unprecedented annual and seasonal-scale warming over the last century with substantial variability superimposed on the trend. Recent summertime T2m conditions and related Greenland ice sheet (GrIS) melt patterns and runoff extremes are linked to warm North Atlantic Ocean surface temperature anomalies and high pressure persistence. Meanwhile regional climatic controls of the island's autumn and winter T2m variations and related processes (e.g. maintenance of snow cold content) are less well understood, yet are important for predicting future GrIS mass balance changes.
In this study, Greenland coastal and lower ablation zone T2m since the 1870s are statistically modeled by preceding and contemporaneous (i.e. lag-2,-1, 0 season), orthogonalized North Atlantic climate indices composed of marginal sea surface temperatures, sea ice concentration, and atmospheric circulation (e.g. Greenland Blocking Index (GBI) and North Atlantic Oscillation (NAO)). We find ~40-70% of west Greenland T2m variance is explained by these indices which tend to show improved predictability (>5%) for ice sheet vs ice-free coastal sites. Results are roughly consistent across autumn and winter, and indicate that the seasonally overlapping GBI-NAO predictor captures the bulk of the total T2m variability (r2=~20-50%). Of note, >40% of autumn and winter Sermeq Kujalleq T2m variability is explained by GBI-NAO behaviors. Multidecadal correlations between GBI-NAO and most T2m series are relatively stable and positive (r>0.50) suggesting consistent air temperature regulation by localized atmospheric blocking. Inclusion of remote tropical and North Pacific climate indices (e.g. Niño 3.4 and Pacific Decadal Oscillation) only modify the model-explained variance by ~±5%, further signaling the importance of local climate forcing and feedbacks to the production of T2m anomalies. Findings suggest that global coupled climate models ability to accurately forecast cold season North Atlantic Arctic lower and mid-troposphere pressure characteristics will be critical to predicting T2m variations and local meteorological conditions that affect GrIS mass balance (e.g. snow vs rain).- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C43D1517B
- Keywords:
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- 0720 Glaciers;
- CRYOSPHERE;
- 0726 Ice sheets;
- CRYOSPHERE;
- 0732 Icebergs;
- CRYOSPHERE;
- 0750 Sea ice;
- CRYOSPHERE