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Mountain glaciers at ∼26–19 ka, during the global Last Glacial Maximum near the end of the last 10 5 yr glacial cycle, are commonly considered on the basis of dating and field mapping in several well-studied areas to have been the largest of the late Quaternary and to have advanced synchronously from region to region. However, a numerical sensitivity model (Rupper and Roe, 2008) predicts that the fraction of ablation due to melting varies across Central Asia in proportion to the annual precipitation. The equilibrium-line altitude of glaciers across this region likely varies accordingly: in high altitude, cold and arid regions sublimation can ablate most of the ice, whereas glaciers fed by high precipitation cannot ablate completely due to sublimation alone, but extend downhill until higher temperatures there cause them to melt. We have conducted field studies and 10 Be dating at five glaciated sites along a precipitation gradient in Mongolia to test the Rupper/Roe model. The sites are located in nearby 1.875 × 1.875° cells of the Rupper/Roe model, each with a different melt fraction, in this little-studied region. The modern environment of the sites ranges from dry subhumid in the north (47.7° N) to arid in the south (45° N). Our findings show that the maximum local advances in the dry subhumid conditions predated the global Last Glacial Maximum and were likely from MIS 3. However, we also found that at ∼8–7 ka a cirque glacier in one mountain range of the arid Gobi desert grew to a magnitude comparable to that of the local maximum extent. This Holocene maximum occurred during a regional pluvial period thousands of years after the retreat of the Pleistocene glaciers globally. This asynchronous behavior is not predicted by the prevailing and generally correct presumption that glacier advances are dominantly driven by temperature, although precipitation also plays a role. Our findings are consistent with and support the Rupper/Roe model, which calls for glaciation in arid conditions only at high altitudes of sub-freezing temperatures, where the melt fraction in ablation is low. We expect a heterogeneous pattern of glacial responses to a changing modern climate in cold arid regions; an individual glacier advance should not be necessarily interpreted as evidence of cooling climate. [ABSTRACT FROM AUTHOR]

The geomorphology of the Denton Hills provides insight into the timing and magnitude of glacial retreats in a region of Antarctica isolated from the influence of the East Antarctic ice sheet. We present 26 Beryllium-10 surface exposure ages from a variety of glacial and lacustrine features in the Garwood and Miers valleys to document the glacial history of the area from 10 to 286 ka. Our data show that the cold-based Miers, Joyce and Garwood glaciers retreated little since their maximum positions at 37.2 ± 6.9 (1σ n = 4), 35.1 ± 1.5 (1σ, n = 3) and 35.6 ± 10.1 (1σ, n = 6) ka respectively. The similar timing of advance of all three glaciers and the lack of a significant glacial expansion during the global LGM suggests a local LGM for the Denton Hills between ca. 26 and 51 ka, with a mean age of 36.0 ± 7.5 (1σ, n = 13) ka. A second cohort of exposure ages provides constraints to the behaviour of Glacial Lake Trowbridge that formerly occupied Miers Valley in the late Pleistocene. These data show active modification of the landscape from ∼20 ka until the withdrawal of ice from the valley mouths, and deposition of Ross Sea Drift, at 10–14 ka. [ABSTRACT FROM AUTHOR]

Quantifying the contribution of the East Antarctic Ice Sheet (EAIS) to sea-level rise during the last deglaciation is complicated by the limited opportunities to constrain ice-sheet models. The nunatak, Escalade Peak, provides a gauge for past ice surface elevation changes and behaviour throughout the last glacial cycle. Geomorphological mapping, geological evidence and 10Be cosmogenic-nuclide exposure dating at Escalade Peak, provide new constraints on the ice surface history of the Skelton Névé since the Last Glacial Maximum (LGM). An elevation transect from the eastern margin of Escalade Peak indicates that the ice surface of the Skelton Névé was at least 50 m and perhaps >120 m higher than present during the LGM. In contrast, surface-exposure ages from a suite of inner moraines (blue-ice moraines) adjacent to Escalade Peak do not provide independent ice surface elevation constraints, but may provide an indirect constraint on the timing of thinning due to exhumation-ablation processes. Maximum simple exposure ages from the inner moraines suggest ice surface ablation was initiated by 19.2 ka, but the majority of ice surface lowering at Escalade Peak likely occurred after ∼15 ka and reached the present-day ice level at ∼6 ka. These findings suggest that slow flowing inland sites of EAIS outlet glaciers, such as southern Skelton Névé, experienced minimal ice surface elevation change since the LGM and record an EAIS outlet glacier and western Ross Sea retreat signature rather than widespread Ross Sea retreat. The ice surface lowering is likely to have been in response to retreat of the grounded ice in the western Ross Embayment causing a reduction in buttressing of the Skelton Glacier and draw down into the Ross Sea. • Ice was at least ∼50 m and perhaps >120 m higher than present during the LGM. • Inner moraines may provide an indirect constraint on the timing of thinning. • The majority of post-LGM ice surface lowering most likely occurred from ∼15 ka. • The retreat history suggests outlet glacier and western Ross Sea retreat signature. [ABSTRACT FROM AUTHOR]