Australia: The Land Where Time Began

A biography of the Australian continent 

Jakobshavn Isbrae – Acceleration Triggered by Warm Subsurface Ocean Waters

Several outlet glaciers in Greenland the Antarctica have been found by observations over the past decades to have accelerated rapidly (Rignot & Kanagaratnam, 2006). A sudden switch of Jakobshavn Isbrae, which is a large outlet glacier that feeds a deep-ocean fjord on the west coast of Greenland,  is one of the largest changes observed, from thickening slowly to thinning rapidly (Thomas et al., 2003) in 1997, that is associated with a doubling of the velocity of the glacier’s flow (Joughin, Abdalati & Fahnestock, 2004). Among the suggestions that have been offered to explain the increased speed of Jakobshavn Isbrae are the lubrication of the interface of ice-bedrock as more meltwater has drained to the bedrock beneath the glacier during warmer summers in recent years (Zwally et al., 2002), and the weakening and breakup of the floating ice tongue that buttressed the glacier (Thomas, 2004). In this paper Holland et al. present hydrographic data which shows there has been a sudden increase in subsurface ocean temperature in 1997 along the entire west coast of Greenland, which suggests the changes in Jakobshavn Isbrae were actually triggered by the arrival of water that was relatively warm that originated in the Irminger Sea near Iceland. These oceanic changes are traced back to changes in the circulation of the atmosphere in the North Atlantic region. The conclusion reached is that the prediction of future rapid dynamic responses of outlet glaciers to changes in climate will require that the understanding of the effects of changes in the regional circulation of oceans and atmosphere on the delivery of warm subsurface waters to the periphery of the ice sheet will be improved.

Sources & Further reading

1. Holland, D. M., R. H. Thomas, B. De Young, M. H. Ribergaard and B. Lyberth (2008). "Acceleration of Jakobshavn Isbrae triggered by warm subsurface ocean waters." Nature Geosci. 1: 659-664.