Ice-shelf – ocean interactions at Fimbul Ice Shelf, Antarctica from oxygen isotope ratio measurements

[摘要] Melt water from the floating ice shelves at the margins of the southeasternWeddell Sea makes a significant contribution to the fresh water budget ofthe region. In February 2005 a multi-institution team conducted anoceanographic campaign at Fimbul Ice Shelf on the Greenwich Meridian as partof the Autosub Under Ice programme. This included a mission of theautonomous submarine Autosub 25 km into the cavity beneath Fimbul Ice Shelf,and a number of ship-based hydrographic sections on the continental shelfand adjacent to the ice shelf front. The measurements reveal two significantsources of glacial melt water at Fimbul Ice Shelf: the main cavity under theice shelf and an ice tongue, Trolltunga, that protrudes from the main icefront and out over the continental slope into deep water. Glacial melt wateris concentrated in a 200 m thick Ice Shelf Water (ISW) layer below the baseof the ice shelf at 150–200 m, with a maximum glacial melt concentration ofup to 1.16%. Some glacial melt is found throughout the water column, andmuch of this is from sources other than Fimbul Ice Shelf. However, at least0.2% of the water in the ISW layer cannot be accounted for by otherprocesses and must have been contributed by the ice shelf. Just downstreamof Fimbul Ice Shelf we observe locally created ISW mixing out across thecontinental slope. The ISW formed here is much less dense than that formedin the southwest Weddell Sea, and will ultimately contribute a freshening(and reduction in δ¹⁸O) to the upper 100–150 m of the watercolumn in the southeast Weddell Sea.

[学科分类] 海洋学与技术