ausblenden:
Schlagwörter:
NORTH-ATLANTIC OSCILLATION; HIGH-RESOLUTION RECORD; ICE CORES; ATMOSPHERIC CIRCULATION; SPATIAL TRENDS; ANNULAR MODES; ACCUMULATION; CLIMATE; VARIABILITY; SUMMIT
Zusammenfassung:
Annually resolved ice core records from different regions over the Greenland Ice Sheet (GrIS) are used to investigate the spatial and temporal variability of calcium (Ca²⁺, mainly from mineral dust) and sodium (Na⁺, mainly from sea salt) deposition. Cores of high common inter-annual variability are grouped with an EOF analysis, resulting in regionally representative Ca²⁺ and Na⁺ records for northeastern and central Greenland.
Utilizing a regression and validation method with ERA-40 reanalysis data, these common records are associated with distinct regional atmospheric circulation patterns over the North American Arctic, Greenland, and Central to Northern Europe. These patterns are interpreted in terms of transport and deposition of the impurities. In the northeastern part of the GrIS sea salt records reflect the intrusion of marine air masses from southeasterly flow. A large fraction of the Ca²⁺ variability in this region is connected to a circulation pattern suggesting transport from the west and dry deposition. This pattern is consistent with the current understanding of a predominantly Asian source of the dust deposited over the GrIS. However, our results also indicate that a significant fraction of the interannual dust variability in NE and Central Greenland are determined by the frequency and intensity of wet deposition during the season of high atmospheric dust loading, rather than representing the variability of the Asian dust source and/or long-range transport to Greenland. The variances in the regional proxy records explained by the streamfunction patterns are high enough to permit reconstructions of the corresponding regional deposition regimes and the associated circulation patterns.
