Identification of frequency changes in synoptic circulation types and consequences for glacier mass balance in Norway

摘要

The cumulative nel mass balances of maritime glaciers in Norway display a net surplus during the period 1963 2000. The articleang on Norwegian maritime glaciers. To icr of synoptic meteorological stations in luslering of component scores to classify rm' type air masses during the summer ,'quency of "cold' cluster types during the eeks to establish the causal mechanisms thai resulted in ihe positive nel balances occur achieve this, a Temporal Synoptic Index (TSI) was derived tor a 30-year period for a numr Norway. The TSI is derived using Principal Components Analysis (PCA) and subsequent Jays for bolh winter and summer seasons. Findings indicate that the occurrence of i months have increased in frequency, particularly since the late 1980s. A reduction in the frwinter months is evident after this period, while the frequency of 'warm' types, with an increased moisture carrying capacity, has increased in frequency. The frequency occurrence of these key air mass types is shown to be significantly related to glacier mass balance during both the accumulation and ablation season. Winter air mass types from maritime source regions act to enhance accumulation and suppress ablution, while summer continental source types suppress accumulation and enhance ablation.