Interannual variability in net accumulation on Tasman Glacier and its relationship with climate

摘要

Mid-latitude maritime glaciers are responding quickly and directly to climate change. This response is expected to continue, and will result in maritime glaciers making a large contribution to sea level rise over the coming decades. Maritime glaciers in the New Zealand Southern Alps provide an opportunity to learn more about climate-glacier mass balance relationships in a high precipitation setting, and how these relationships might change in the future. Ice core and direct glaciological measurements are used to construct a 24-year record of net accumulation, the longest of its type in New Zealand. We demonstrate that variations in net accumulation on Tasman Glacier are more strongly influenced by temperature than by precipitation. Further, it is temperature during the ablation season that exerts most control. Atmospheric circulation patterns, in particular the state of the El Nino Southern Oscillation (ENSO) and Southern Annular Mode (SAM), were found to influence net accumulation. When the SAM is positive and the ENSO in a La Nifta phase, easterly and northerly wind anomalies are enhanced, temperatures increase in the Southern Alps region and more negative glacier mass balances result. Conversely when SAM is negative and ENSO in an El Nifio phase, westerly and southerly wind anomalies occur, and temperatures decrease in the Southern Alps region. In this case, glacier mass balance is more likely to be positive. However, relationships between glacier mass balance and these atmospheric circulation modes are not simply linear, with some of the lowest net accumulation years associated with inverse polarity between the SAM and the ENSO.