Abstract
Recognition of how dynamic the Antarctic ice sheets and glaciers were during the late Holocene has grown in recent years. Proxy data suggests the presence of Neoglacial advances but few moraines or glacial features from this time have been dated compared to glaciated landscapes of the Northern Hemisphere. Debate continues on whether parts of Antarctica experienced glacial advance at the same time as the “Little Ice Age” (LIA), which is well-documented in the Northern Hemisphere. We provide new evidence for late Holocene glacial fluctuations at three locations along the Antarctic Peninsula. A moraine or till sheet from a tidewater glacier cross cuts a series of dated raised beaches at Tay Head, Joinville Island along the northwestern Weddell Sea. At Spark Point, on Greenwich Island, a glacier has overrun Holocene raised beaches and a shell-bearing marine deposit is reworked into a glacial diamicton. A third site in Calmette Bay within the larger Marguerite Bay also contains a recent moraine that cuts across a series of dated raised beach ridges. The new ages constraining these glacial advances are in broad agreement with the handful of other existing ages on moraines and proxy records suggestive of cooler conditions within the Antarctic Peninsula. Combining available timing constraints into a Bayesian model yields an age of 400 to 90 cal BP (1550–1860 CE; 95%) for the LIA across the Antarctica Peninsula. Consideration of a two-phase glacial advance within our Bayesian framework does fit more of the data from across the Antarctic Peninsula and suggests advances from 575 to 330 cal BP (1375–1620 CE) and 400 to 50 cal BP (1550–1900 CE). However, more work is needed to determine if such a two-phase advance occurred. Regardless, its similar timing within the Antarctic Peninsula to that of the Northern Hemisphere supports recent assertions of a volcanic or solar forcing for the LIA. These recent readvances also provide a possible mechanism for changes in the rates of Holocene relative sea-level change recorded across the Antarctic Peninsula suggesting that the Antarctic ice sheets may have been more responsive to past climate changes than previously thought and glacial isostatic adjustment from the LIA and possibly other Holocene glacial oscillations is superimposed upon the longer relaxation from the Last Glacial Maximum.
Highlights
The Antarctic ice sheets are the largest reservoirs of freshwater and potential sea-level rise on the planet, and play an important glacial advances throughout Northern Europe and North America (Grove, 2004; Mann et al, 2009) from approximately 1500 to 1800 CE (PAGES 2k Consortium, 2013)
All new radiocarbon ages are reported as calibrated years before present and were calibrated using Calib 8.2 (Stuiver et al, 2021), the MARINE20 calibration curve (Heaton et al, 2020), and a marine radiocarbon reservoir offset (DR) of 635 ± 42 based on the updated version of the Hall et al (2010) reservoir corrected to the MARINE20 calibration curve
We identified glacial moraines representing a recent glacial advance that occurred within the last ~800 years and possibly as recently as 370 calibrated years before present (cal BP) at three locations across the Antarctica Peninsula
Summary
The Antarctic ice sheets are the largest reservoirs of freshwater and potential sea-level rise on the planet, and play an important glacial advances throughout Northern Europe and North America (Grove, 2004; Mann et al, 2009) from approximately 1500 to 1800 CE (PAGES 2k Consortium, 2013). Clapperton and Sugden, 1988; Hall, 2007; Guglielmin et al, 2016; Kaplan et al, 2020), but they could have occurred asynchronously due to local effects (PAGES 2k Consortium, 2013) They could be archives of a true, yet undetermined, synchronous LIA glacial advance in the Antarctic Peninsula. The Antarctic Peninsula is one of the fastest warming locations in the world, with surface temperatures increasing by over 2.5 C during the latter half of the 20th century (Vaughan et al, 2003) It experiences a maritime subpolar climate and contains several icefree islands and peninsulas most notably the South Shetland Islands, the islands around James Ross Island in the Eastern Antarctic Peninsula (EAP), and the islands in and around Marguerite Bay. Today the region experiences significant differences in climate on its western and eastern sides (Reynolds, 1981; Morris and Vaughan, 2003; van Wessem et al, 2016). Isotherms dip farther south on the WAP than the EAP making the WAP warmer and causing it to experience higher rates of precipitation (Reynolds, 1981; Morris and Vaughan, 2003; Thomas et al, 2015, 2017, 2017; van Wessem et al, 2016)
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