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While the effects of volcanism on Earth’s climate are well understood, the volcano-ice sheet system hosts a two-way feedback. Volcanic activity promotes ice melting, which in turn affects the internal dynamics of the magma chamber below. At present, accurate forecasts of sea-level rise hinge on the stability of the West Antarctic Ice Sheet, and thus require consideration of subglacial volcano-deglaciation feedbacks. The West Antarctic Ice Sheet, grounded below sea-level, is particularly vulnerable to collapse, yet its position atop an active volcanic rift is seldom considered. Ice unloading raises the geotherm and alters the crustal stress field, impacting dike propagation. However, the consequences on internal magma chamber dynamics and thus long-term eruption behavior remain elusive. Given potential for unloading-triggered volcanism in West Antarctica to accelerate ice retreat, we adapt the thermomechanical magma chamber model of Scholz et al. (2023) for West Antarctic Rift basalts, simulating a shrinking ice load through a prescribed decrease of lithostatic pressure. Examining different unloading scenarios, we investigate the impacts on volatile partitioning within the magma and eruptive trajectory across a wide range of initial magma chamber conditions. Pressurization of a magma chamber beyond a critical threshold results in eruption, delivering enthalpy to the ice. Considering the removal of km-thick ice sheets, we demonstrate the rate of unloading is dominant in influencing the cumulative mass erupted and consequently, heat released to the ice. These findings provide fundamental insights into the complex volcano-ice interactions in West Antarctica and other subglacial volcanic settings. 

At Lago Buenos Aires, Argentina, 10 Be, 26 Al, and 40 Ar/ 39 Ar ages range from 190,000 to 109,000 yr for two moraines deposited prior to the last glaciation, 23,000—16,000 yr ago. Two approaches, maximum boulder ages assuming no erosion, and the average age of all boulders and an erosion rate of 1.4 mm/10 3 yr, both yield a common estimate age of 150,000—140,000 yr for the two moraines. The erosion rate estimate derives from 10 Be and 26 Al concentrations in old erratics, deposited on moraines that are >760,000 yr old on the basis of interbedded 40 Ar/ 39 Ar dated lavas. The new cosmogenic ages indicate that a major glaciation during marine oxygen isotope stage 6 occurred in the mid-latitude Andes. The next five youngest moraines correspond to stage 2. There is no preserved record of a glacial advance during stage 4. The distribution of dated boulders and their ages suggest that at least one major glaciation occurred between 760,000 and >200,000 yr ago. The mid-latitude Patagonian glacial record, which is well preserved because of low erosion rates, indicates that during the last two glacial cycles major glaciations in the southern Andes have been in phase with growth and decay of Northern Hemisphere ice sheets, especially at the 100,000 yr periodicity. Thus, glacial maxima are global in nature and are ultimately paced by small changes in Northern Hemisphere insolation.