Combined oceanic and atmospheric influences on net accumulation on Devon Ice Cap, Nunavut, Canada

Abstract

AbstractAn annual net accumulation history of the high-elevation region of Devon Ice Cap, Nunavut, Canada, was reconstructed for the period 1963–2003 using five shallow firn cores. Annual net accumulation decreased significantly after 1989. To explain variability in the reconstructed annual net accumulation record, monthly and seasonal moisture-source probabilities were calculated for gridcells throughout the Arctic during 1979–2003. Seasonally, moisture-source probabilities reach a maximum in northern Baffin Bay in late summer/early fall and approach zero throughout the Arctic in winter. Late-summer/early-fall moisture-source probabilities were significantly higher around the North Open Water (NOW) Polynya during the 4 year period of highest annual net accumulation during the 1979–2003 period (1984–87), than during the 4 year period with the lowest annual net accumulation (1994–97). This is due to both a significant decrease in the sea-ice fraction and a significant increase in low-elevation atmospheric transport over the NOW area during the high net accumulation period. Anomalously low net accumulation and anomalously high firnification rates during the 1989–2003 period suggest that a change in ice dynamics, rather than a change in surface mass balance, may explain recent ice-cap thickening observed by laser altimetry.