The majestic giant icebergs of the Antarctic may be responsible for hampering sea-ice production and slowing deep ocean movement needed to regulate the global climate, according to a study by French and Canadian researchers.
The scientists looked at fossils embedded deep in the East Antarctic’s Mertz Glacier and suggest it has been snapping off to generate the huge icebergs about every 70 years.
The Mertz Glacier Tongue protrudes tens of kilometres into the Southern Ocean and shelters a highly productive environment.
As the sea-ice is formed, large quantities of salt are expelled into the ocean, generating about 25% of the dense Antarctic bottom waters responsible for driving heat and salt around the planet.
In February 2010, a huge iceberg collided with the Mertz Glacier Tongu, creating an 80 kilometre-long iceberg which inhibited local sea-ice formation.
Whether this calving represents an isolated event or is part of a longer-term regime remains unclear.
Xavier Crosta of the Universite de Bordeaux and colleagues analysed fossilised plankton and chemical compounds from a 250-year long sediment core retrieved from the sea floor downstream of the Mertz Glacier.
The authors reveal that sea-ice conditions and bottom water production varied about every 70 years over the past 250 years, suggesting a longer-term regime is in place.
Given the local dominance of the Mertz Glacier it is likely that these 70 year cycles are set by the glacier’s calving dynamics.
However, icebergs released from other nearby glaciers, in addition to regional patterns of atmospheric variability may also play a role.
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