Geomorphic expression of collapsing ice streams revealed by latest generation swath bathymetry images

• There is now a substantial swath bathymetry data set from Antarctica that reveals subglacial bedforms, in particular mega-scale glacial lineations, which were formed by ice streams that occupied glacial troughs during the LGM. However, with the exception of grounding zone wedges, few studies have yielded high-resolution sea floor images that show geomorphic features formed by retreating ice streams. For example, deep-tow side-scan sonar records from Ross Sea show a range of recessional features, mostly 1-3 meters high, that overprint mega-scale glacial lineations. These features were not imaged in swath bathymetry records. During the 2010 austral summer, the Swedish ice breaker Oden was used to conduct an extensive survey in the sparsely studied central trough in Pine Island Bay using the latest generation multibeam technology. The bedforms imaged in Pine Island Bay are similar to small-scale recessional features previously imaged in Ross Sea using deep-tow side-scan sonar. These include fishbone moraines and corrugated iceberg furrows, which we argue were produced daily through tidally-influenced motion of a disintegrating ice shelf. During this event a 65 km long stretch of the trough was cleared of floating ice in about 1.5 years. The break-up occurred ~12,000 cal ka BP and was likely a response to rapid sea-level rise at that time. Acquisition of more high-resolution swath bathymetry data should greatly increase our understanding of ice stream interaction with the seafloor and those factors that have influenced ice stream behavior during retreat. Future work should focus on the rugged inner shelf, were subglacial meltwater is believed to have contributed to ice stream instability.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

Nyckelord

Marine Geoscience

marin geovetenskap

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