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Crystalline erratics from the Antarctic Peninsula on northern James Ross Island (Photograph: Ó. Ingólfsson, 1989).
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Glaciers and ice sheets have existed in Antarctica for more than 30My, and it is the most stable cryospheric system on Earth. This article starts with a very brief overview of the pre-Quaternary glacial history of Antarctica. The Pleistocene history of the Antarctic Ice Sheet is outlined, and the glacial history of Antarctica since the Last Glacial...
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Context 1
... of more extensive ice cover than today exists all along the Antarctic Peninsula in the form of ice-abraded ridge crests at high altitudes, striated bedrock on presently ice-free islands, erratics (Fig. 6) and thin till deposits, as well as raised beach and marine deposits (John & Sugden, 1971;Sugden & John, 1973;Curl, 1980;Clapperton & Sugden, 1982Ingólfsson et al., 1992), whereas ancient glacial trimlines are rarely described. Systematic attempts to map altitudinal evidence of LGM ice-thickness in the Antarctic Peninsula region have ...
Context 2
... coincides well with the oldest radiocarbon date on a bivalve from a core in McMurdo Sound, w hich gives 6.5 ka BP as the minimum age of grounding line retreat from the Sound ( Licht et al., 1996). The marine limit becomes gradually younger southwards, Figure 16. The Ross Sea- Victoria Land region, with minimum ages for deglaciation. ...
Context 3
... Holocene glacier oscillations -There is some information available as to mid-to late-Holocene glacier variations in Victoria Land. Raised beaches in the area between Explorers Cove and Marble Point (Fig. 16), 14 C dated to c. 5 ka BP, terminate against the Wilson Piedmont Glacier and presumably extend beneath the ice (Hall & Denton 2000b). This suggests that the Wilson Piedmont Glacier has expanded since 5 ka BP. After the deglaciation in Terra Nova Bay, the ice shelves entering the bay were less extensive than today , Baroni, 1994, ...
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Grounding lines are a key indicator of ice-sheet instability, because changes in their position reflect imbalance with the surrounding ocean and affect the flow of inland ice. Although the grounding lines of several Antarctic glaciers have retreated rapidly due to ocean-driven melting, records are too scarce to assess the scale of the imbalance. He...
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Geothermal heat flux (GHF) is an important part of the basal heat budget of continental ice sheets. The difficulty of measuring GHF below ice sheets has directly hindered progress in understanding of ice sheet dynamics. We present a new GHF measurement from below the West Antarctic Ice Sheet, made in subglacial sediment near the grounding zone of t...
Citations
... However, caution is needed in using TCN dating on samples originating from nonerosive cold-based ice that might yield erroneously old apparent exposure ages (Nyvlt et al., 2020). Several works in the Antarctic Peninsula also indicate that ice volumes might have been much more prominent before 35 ka (lLGM) than gLGM (e.g., Bentley and Anderson, 1998;Hjort et al., 2003;Ingolfsson, 2014;Ó 'Cofaigh et al., 2014). ...
Whether glaciers in the southern hemisphere were asynchronous to those in the north during the global Last Glacial Maximum (gLGM; 26.5–19 ka) is still debated. In Patagonia (South America), numerous ice lobes attained their maximum extents during diverse episodes of the last glacial cycle. To understand the variations in the gLGM vs local LGM record, we studied the Lago Aníbal Pinto area (52°00′ S, 72°40′ E; Chile), where several moraine belts were deposited by one of the eastward-flowing southern Patagonian Ice Sheet (PIS) outlet ice lobes; the Última Esperanza. We report eight ¹⁰Be terrestrial cosmogenic nuclides (TCN) surface ages from granitic moraine boulders. Our weighted average age obtained from the southern part of the Río Turbio moraine belt yields 50.7 ± 2.4 ka (oldest boulder age; 53.8 ± 5.3 ka) and confirms the greatest extent of the local Last Glacial Maximum (lLGM) during Marine Isotope Stage 3 (MIS 3) in the previously dated northern moraines from the same belt. Our ¹⁰Be TCN age (32.6 ± 2.2 ka) derived from the Dos Lagunas moraine, which makes up the northernmost margin of the Última Esperanza ice lobe's Arauco advance, also validates the MIS 3 timing. Following the formation of Arauco moraines, the Última Esperanza ice lobe was split into three main tributaries in the south, which formed three restricted and previously undated moraine complexes. We dated one of them, the Aníbal Pinto moraine complex. Whereas the highest moraine yielded the oldest age (28.3 ± 2.2 ka), lower moraine's surface that was later truncated as a lacustrine erosional platform, yielded younger boulder ages (weighted average age = 18.9 ± 1.0 ka; oldest boulder age = 19.0 ± 1.5 ka), indicating they were deposited under the Pinto Lake level. Our new age data allow us to propose a new chronology for the Aníbal Pinto moraine complex and consolidate previously published ages from other moraine belts. We attribute the Aníbal Pinto moraine complex to early gLGM (MIS 2), emphasising that the gLGM was half the extent of lLGM in the Última Esperanza ice lobe that underpins its interhemispheric asynchronous character.
