LATE QUATERNARY ICE ELEVATION OF HATHERTON GLACIER, ANTARCTICA

During Marine Isotope Stage 2 (MIS-2), grounded ice in the Ross Sea extended to a limit near Coulman Island (73.5° S). Glaciers draining the East Antarctic Ice Sheet through the Transantarctic Mountains thickened by ~1000 m in the southern Ross Sea, but receded in the McMurdo Dry Valleys. We have mapped and dated deposits alongside Hatherton Glacier, a tributary of Darwin Glacier, between these two regions. In earlier work, Bockheim et al. (1989) mapped Hatherton Glacier deposits and assigned a Last Glacial Maximum (LGM) age to the Britannia II drift and a post-LGM age to the Britannia I drift based on minimal rock weathering and on radiocarbon ages of subfossil algae in former ice-marginal ponds. Storey et al. (2010) and Joy et al. (2014) dated deposits at Lake Wellman, Dubris and Bibra Valleys with cosmogenic nuclides; they inferred an MIS-6 age for Britannia-II drift, little or no thickening of Hatherton Glacier and Ross Sea ice during MIS-2 and interpreted Britannia I drift as an early Holocene re-advance. Our initial mapping shows that the two Britannia limits are distinct at Dubris Valley, but they may coincide at Lake Wellman. Initial exposure ages from the Britannia II limit at Dubris Valley indicate that it is older than 130 ka. Ages from Britannia I drift limits on bedrock above Dubris and Bibra Valleys are 8.5 ± 0.3 ka and 7.1 ± 0.3 ka. An elevation transect below the Britannia I limit shows that Hatherton Glacier thinned by >150 m over ~1,700 years starting after 7.1 ± 0.3 ka. This thinning continued into the late Holocene. Algae samples at the Britannia I limit at Lake Wellman are early Holocene in age. Thus, maximum ice thickness was achieved at Lake Wellman before Dubris Valley, up-glacier. This difference in the timing of maximum ice thickening is similar to behavior observed for other Transantarctic Mountains outlet glaciers, where ice thickness on the lower glacier is coupled to grounding-line position in the Ross Sea, but thickness of the upper glacier is sensitive to increased Holocene accumulation on the East Antarctic plateau.

References: Bockheim et al., Quat. Res. 31, 229 (1989); Storey et al., Ant. Sci. 22, 603 (2010); Joy et al., Quat. Sci. Rev., 83, 46 (2014). Supported by NSF award PLR-1246110.