Abstract
The West Antarctic ice sheet (WAIS) is highly vulnerable to collapsing because of increased ocean and surface temperatures. New evidence from ice core tephra shows that subglacial volcanism can breach the surface of the ice sheet and may pose a great threat to WAIS stability. Micro-CT analyses on englacial ice core tephra along with detailed shard morphology characterization and geochemical analysis suggest that two tephra layers were derived from subglacial to emergent volcanism that erupted through the WAIS. These tephra were erupted though the center of the ice sheet, deposited near WAIS Divide and preserved in the WDC06A ice core. The sources of these tephra layers were likely to be nearby subglacial volcanoes, Mt. Resnik, Mt. Thiel, and/or Mt. Casertz. A widespread increase in ice loss from WAIS could trigger positive feedback by decreasing ice mass and increasing decompression melting under the WAIS, increasing volcanism. Both tephra were erupted during the last glacial period and a widespread increase in subglacial volcanism in the future could have a considerable effect on the stability of the WAIS and resulting sea level rise.
Highlights
The West Antarctic ice sheet (WAIS), a large and unstable marine-based ice sheet, is highly vulnerable to accelerating ice loss caused by erosion of buttressing ice shelves by upwelling warm ocean water[1] and could be impacted by subglacial volcanic eruptions[2, 3]
Several studies using remote sensing techniques have suggested the presence of active subglacial volcanism in West Antarctica
We present the first geochemical and volcanological evidence of subglacial volcanism occurring beneath WAIS obtained directly from associated tephra layers
Summary
The West Antarctic ice sheet (WAIS), a large and unstable marine-based ice sheet, is highly vulnerable to accelerating ice loss caused by erosion of buttressing ice shelves by upwelling warm ocean water[1] and could be impacted by subglacial volcanic eruptions[2, 3]. X-ray micro-computed tomography (μCT) of in situ particles in ice-bound tephra layers allows a 3-dimensional view of the distribution and grain size of particles in three distinct and coarse tephra layers from the WAIS Divide ice core (WDC06A). This is the first time volcanic particles in ice have been imaged to see how particle shape and size vary with depth in the ice core, and this may prove to be a useful tool to help understand and characterize the eruptive history and tephra deposition processes. The presence of relatively recent subglacial volcanism in West Antarctica highlights the potential threat of West Antarctic volcanism to future ice sheet stability
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