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Submarine glacial landforms and interactions with volcanism around Sub-Antarctic Heard and McDonald Islands

conference contribution
posted on 2023-05-24, 17:26 authored by Watson, S, Jodi FoxJodi Fox, Post, A, Joanne WhittakerJoanne Whittaker, Vanessa LucieerVanessa Lucieer, Rebecca CareyRebecca Carey, Mike CoffinMike Coffin, Hodgson, D, Hogan, K, Graham, AGC, Picard, K
Unravelling the glacial history of Sub-Antarctic islands can provide clues to past climate and Antarctic ice sheet stability. The glacial history of many sub-Antarctic islands is poorly understood, including the Heard and McDonald Islands (HIMI) located on the Kerguelen Plateau in the southern Indian Ocean.

The geomorphologic development of HIMI has involved a combination of construction via hotspot volcanism and mechanical erosion caused by waves, weather, and glaciers. Today, the ~2.5 km2 McDonald Islands are not glacierised; in contrast, the ~368 km2 Heard Island has 12 major glaciers, some extending from the summit of 2813 m to sea level. Historical accounts from Heard Island suggest that the glaciers were more extensive in the 1850s to 1870s, and have retreated at least 12% (33.89 km2) since 1997. However, surrounding bathymetry suggests a much more extensive previous glaciation of the HIMI region that encompassed ~9,585 km2, likely dating back at least to the Last Glacial Maximum (LGM) ca. ~26.5 -19 ka.

We present analyses of multibeam bathymetry and backscatter data, acquired aboard RV Investigator in early 2016, that support the previous existence of an extensive icecap. These data reveal widespread ice-marginal and subglacial features including moraines, over-deepened troughs, drumlins and crag-and-tails. Glacial landforms suggest paleo-ice flow directions and a glacial extent that are consistent with previously documented broad scale morphological features. We identify >660 iceberg keel scours in water depths ranging from ~150 - 530 m. The orientations of the iceberg keel scours reflect the predominantly east-flowing Antarctic Circumpolar Current and westerly winds in the region.

40Ar/39Ar dating of volcanic rocks from submarine volcanoes around McDonald Islands suggests that volcanism and glaciation coincided. The flat-topped morphology of these volcanoes may result from lava-ice interaction or erosion by glaciers post eruption during a time of extensive ice-sheet cover and/or wave base erosion during sea level low stands.

The prevalence and range of glacial landforms around HIMI suggest extensive past glaciation, and that glaciers have exerted a major influence on submarine geomorphology.

History

Publication title

AGU Fall Meeting Abstracts

Volume

OS34A-01

Department/School

Institute for Marine and Antarctic Studies

Event title

AGU Fall Meeting

Event Venue

New Orleans, USA

Date of Event (Start Date)

2017-12-11

Date of Event (End Date)

2017-12-15

Repository Status

  • Restricted

Socio-economic Objectives

Assessment and management of terrestrial ecosystems

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