[A-CC33] アイスコアと古環境モデリング

[ACC33-03] The warm anomaly of Antarctic snowfall events and its impact on snow-based temperature proxy

*Aymeric Pierre Marie Servettaz¹、Cécile Agosta²、Christoph Kittel^3,4、Anaïs J. Orsi⁵ (1.Japan Agency for Marine-Earth Science and Technology、2.Laboratoire des Sciences du Climat et de l’Environnement, Université Paris-Saclay、3.Department of Geography, UR SPHERES, University of Liège、4.Institut des Géosciences de l’Environnement, University Grenoble Alpes、5.Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia)

キーワード：Antarctica, Temperature, Snowfall

The cold and dry climate of Antarctica contrasts with occasional warm and moist air intrusions responsible for the largest snowfall events. Recent studies tend to show that a few precipitation events are responsible for most of the annual accumulation and the accumulation variability, resulting in a skewed distribution, where heavy snowfall events have disproportionately large impact on local climate. The warming effect of snowfall events has also previously been evidenced, notably through the breaking of near-surface temperature inversion. Here we use a regional climate model to study temperature changes associated with snowfall events, over the entire Antarctic continent and through the seasons, based on snowfall-weighted temperature. We find that the temperature anomaly scales with snowfall rate, with higher temperature for the largest snowfall events. This scaling effect is particularly pronounced for high elevation sites with low annual accumulation. The positive temperature anomalies are strongly marked in winter snowfall events, and this reduces the seasonal amplitude of snowfall-weighted temperature. Intermittency and irregularities in interannual snowfall induces variability in the snowfall-weighted temperature, which is 80% more variable from one year to another than annually averaged temperature. Since water isotopes are carried by snow and deposited during precipitation events, they usually acquire a temperature signal that strongly correlates with snowfall-weighted temperature. The findings for snowfall-weighted temperature here may apply for the interpretation of water stable isotopes, primarily used for past temperature reconstructions from ice cores.