Tidewater Glaciers Melting Faster Than Previously Thought

Panoramic view of the LeConte Glacier ice front in August 2016. The southern side of the glacier (right side of picture) hangs on a bedrock bump out of the water, yet the deepest portion of the fjord is found just to the left of that area. (Dave Sutherland / University of Oregon)

(CN) – A magnified rate of melting measured at an Alaska glacier is causing scientists to press for reevaluation of existing models of worldwide tidewater glacier loss, according to a study published Thursday in the journal Science.

There are two main types of glaciers: tidewater, where the ice meets the ocean and terrestrial, confined mainly to high-altitude mountainous regions. Researchers focused on tidewater glaciers that are more dynamic and subject to ongoing changes driven by underwater melting and iceberg calving where the ocean meets the ice.

Scientists conducted multibeam sonar surveys on the LeConte Glacier in Southeast Alaska, a typical tidewater glacier that acts like a vast frozen river flowing from the land and into the sea, forming a partially submerged ice-ocean boundary. The sonar images were used to document and create a time-variable, three-dimensional record of changes in the glacier face that could be linked to melting and calving patterns, according to the study authors.

The sonar surveys of the submerged face of the glacier combined with other data on the ocean, ice and atmosphere collected in August 2016 and May 2017 showed twice the magnitude of underwater melting than previously estimated. Research discovered seasonally increasing submarine melt across the glacier face and at rates far greater than theory-based predictions.

“The study’s results, based on direct measurements, suggest that some glaciers may be in ‘hotter water’ than previously thought,” lead author David Sutherland, Department of Earth Sciences at University of Oregon, wrote in a statement.

Worldwide climate change research has come to recognize that ice loss from glaciers influences the rate of sea level rise and global ocean circulation – both drivers of global climate. Up to this point, data is sparse and the understanding of the dynamics of tidewater glacier melt in response to increasingly warming oceans has been made through indirect inferences and an unconstrained theoretical model of subsurface melting, according to the study.

So far, no direct measurements of submarine melting at tidewater glacier fronts have been made. Sutherland and his colleagues point to the results of their study as proof of the pressing need for more substantive data collection in order to reevaluate models to predict glacier loss and the impact on climate change as sea levels rise.

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