Impact assessment of climatic warming on glaciers and ice shelves on northeastern Antarctic Peninsula

Pedro Skvarca and Hernán De Angelis
Instituto Antártico Argentino, Cerrito 1248, C1010AAZ Buenos Aires, Argentina

Contact: glacio@dna.gov.ar

In our paper we will try to assess the impact of the regional climatic warming on ice masses in the northeastern Antarctic Peninsula (AP) region. Drastic changes on both grounded and floating glaciers, associated with the increasing regional climatic warming took place during the last three decades and are augmenting at present along the northeastern side of AP. The striking fact is that some changes, like the disintegration and collapse of the northern Larsen Ice Shelf are occuring with unexpected rapidity, probably in response to the pronounced summer warming trend of the last decade. To improve our knowledge on changes currently under way, recent field measurements and climate data will be analysed and presented.

The mean summer temperature (MST) is a very important climatic parameter for the mass balance and existence of glaciers and ice shelves. The weather stations located in the Drake Passage and along the northeastern AP reveal that the MST's in Antarctic summer 2001-02 were the highest ever recorded since the instrumental measurements begun in this region. At Orcadas station was recorded +1.9 °C, the highest MST since 1903-04; the summer temperatures at Esperanza station reached the historical maximum of +2.4 °C in 50 years and the climatic record of Marambio station shows a maximum MST (+0.7 °C) since the initiation of measurements three decades ago. Analysis of climatic records of these stations also reveals that the mean annual temperature (MAT) trends are more significant towards the lower latitudes and increasing. For instance, the MAT trend at Marambio has increased by 25% in the recent five years. This is mainly due to the increase in mean autumn temperatures trend (+0.12 °C/year). According to available temperature records the last two decades were the warmest of the 20th century and 1999 the warmest year of the record on northeastern AP. Despite the very large variability in both seasonal and annual temperatures, all records show a significant warming trend.

Associated with the increasing warming trend of the last three decades a large thinning rate and negative mass balance were measured on a glacier with termini on land on Vega island, which can be regarded as directly linked to climatic change. Clear signals of glacier surface lowering were also detected on James Ross Island, where the monitoring of tidewater glaciers with satellite imagery indicates increasing retreat rates during the last decade. However, the most striking evidence of the impact induced by the regional climatic warming is the steady retreat of the northern Larsen Ice Shelf since 1975, which culminated with the disintegration of Larsen A in 1994-95 and the northern half of Larsen B in 2001-02, in coincidence with the warmest summers in the region. Since 1975 the Larsen Ice Shelf north of Jason Peninsula (66° S) lost about 12000 km², of which 10000 km² disintegrated during the past ten years.