Showing papers by "Noel Gourmelen published in 2013"

Sustained retreat of the Pine Island Glacier

Abstract: We use satellite observations to show that, between 1992 and 2011, the Pine Island Glacier hinge line retreated at a rate of 0.95 ± 0.09 km yr−1 despite a progressive steepening and shoaling of the glacier surface and bedrock slopes, respectively, which ought to impede retreat. The retreat has remained constant because the glacier terminus has thinned at an accelerating rate of 0.53 ± 0.15 m yr−2, with comparable changes upstream. This acceleration is consistent with an intensification of ocean-driven melting in the cavity beneath the floating section of the glacier. The pattern of hinge-line retreat meanders and is concentrated in isolated regions until ice becomes locally buoyant. Because the glacier-ocean system does not appear to have reached a position of relative stability, the lower limit of sea level projections may be too conservative.

Controls on short-term variations in Greenland glacier dynamics

Abstract: Short-term ice-dynamical processes at Greenland’s Jakobshavn and Kangerdlugssuaq glaciers were studied using a 3 day time series of synthetic aperture radar data acquired during the 2011 European Remote-sensing Satellite-2 (ERS-2) 3 day repeat campaign together with modelled meteorological parameters. The time series spans the period March–July 2011 and captures the first 30% of the summer melting season. In both study areas, we observe velocity fluctuations at the lower 10 km of the glacier. At Jakobshavn Isbrae, where our dataset covers the first part of the seasonal calving-front retreat, we identify ten calving episodes, with a mean calving-front area loss of 1.29 0.4km2. Significant glacier speed-up was observed in the near-terminus area following all calving episodes. We identify changes in calving-front geometry as the dominant control on velocity fluctuations on both glaciers, apart from a

Towards a glacier velocity field at the scale of the Himalayas

Abstract: Himalayan glaciers are under pressure due to climate change but spatial and temporal characteristics of glaciers change are not very well constrained. The fate of Himalayan glaciers is particularly important for local populations and for understanding the various patterns of climate change in the region. Thus it is important to quantify their evolution over the last decades to be able to understand future dynamic. Recent studies focus only on restricted areas, over a short time­scale whereas the diversity of the himalayan glaciers requires to work on a global scale and a time scale that is larger than the climatic variability. Glaciers' velocity is an important variable to characterise glaciers' evolution and dynamics. The Landsat archive with its global coverage and 40 years of temporal coverage is a major EO dataset for improving the spatial and temporal resolution of Himalayan glaciers' change. Here we present the premice of a fully automated processing chain used to derive glacier velocity for the entire himalayan range for the period 1972-2013.