HOLOCENE ACCUMULATION RATES IN ANTARCTIC PENINSULA FJORDS: FROM MILLENNIAL TO RECENT TIMESCALES

The Antarctic Peninsula (AP) is among the most rapidly warming regions on Earth. Such warming has been labeled as the culprit of accelerated glacial retreat and loss of ice shelves in the region. The dynamic environment of the AP presents a unique opportunity to test whether rapidly retreating ice leaves behind a distinct signature in the sedimentary record and, if so, how to identify that signature in older sediments. Accumulation rates are calculated using ¹³⁷Cs for decadal timescales, and ¹⁴C for millennial timescales, and they are compared with published rates from ²¹⁰Pb analyses. The study areas span both east and west AP, including Maxwell Bay, Firth of Tay, Herbert Sound, Lapeyrere Bay, Andvord Bay, Flandres Bay, Beascochea Bay, and Neny Fjord. Preliminary results show considerable variability in accumulation rates, geographically and temporarily. Rates calculated using ¹³⁷Cs vary between 2 mm/yr in Beascochea Bay and 8 mm/yr in Flandres Bay, while ¹⁴C-derived rates range from 0.6 mm/yr in Lapeyrere Bay to 4 mm/yr in Maxwell Bay. Our results suggest that recent accumulation rates are higher than millennial timescale rates. Our data also shows that accumulation rates do not vary significantly with distance from the fjord head. Possible causes for this may be related to glacier-fjord configuration, since several AP fjords are flanked by multiple glaciers, which contribute sediment along the profile of the fjord. In addition, efficient sediment dispersal mechanisms may redistribute this sediment. Millennial timescale accumulation rates are similar across broad latitudinal transects, from Maxwell Bay to Beascochea Bay. This suggests that geographic location and climate are not the only controls on glacier retreat and sediment input within fjords. Other factors such as hypsometry, bedrock resistance to erosion, glacier configuration, and the physiography of the fjord may also be influential. For this reason and in order to investigate recent accelerated retreat rates of tidewater glaciers, gaining a better understanding of sediment flux for any given fjord or bay requires data that spans a range of timescales and sample locations.