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Subglacial freshwater discharge from beneath Antarctic glaciers likely has a strong impact on ice shelf basal melting. However, the difficulty in directly observing subglacial flow highlights the importance of modeling these processes. We use an ocean model of the Totten Ice Shelf cavity into which we inject subglacial discharge derived from a hydrology model applied to Aurora Subglacial Basin. Our results show (a) discharge increases melting in the vicinity of the outflow region, which correlates with features observed in surface elevation maps and satellite‐derived melt maps, with implications for ice shelf stability; (b) the change in melting is driven by the formation of a buoyant plume rather than the addition of heat; and (c) the buoyant plume originating from subglacial discharge‐driven melting is far‐reaching. Basal melting induced by subglacial hydrology is thus important for ice shelf stability, but is absent from almost all ice‐ocean models. Plain Language Summary Grounding line subglacial discharge is the outflow of freshwater at the region where Antarctic ice shelves begin to float. This process is difficult to observe as the outflow region is typically below ice up to several kilometers thick. Using a computer model, we show how the outflow of this fresh water melts the underside of an Antarctic ice shelf. We demonstrate that the outflow leads to a strong increase in melting, which is driven not by the heat in the outflow, but rather by the low salinity water's buoyancy. This buoyancy leads to the formation of a plume that rapidly ascends the underside of the ice shelf and can carry even warmer water to the ice, leading to increased melting. Given that melting of ice shelves can destabilize the grounded ice upstream of the floating region, we show that the relationship between subglacial discharge and ice shelf melt is important for understanding the stability of Antarctic ice. Key Points Subglacial discharge has a strong local effect on melting beneath the Totten Ice Shelf Addition of buoyancy explains the change in melting Discharge has far‐reaching impacts due to the extent of the buoyant plume

Totten Glacier is a fast‐moving East Antarctic outlet with the potential for significant future sea‐level contributions. We deployed four autonomous phase‐sensitive radars on its ice shelf to monitor ice‐ocean interactions near its grounding zone and made active source seismic observations to constrain gravity‐derived bathymetry models. We observe an asymmetry in basal melting with mean melt rates along the grounding zone differing by up to 20 m/a. Our new bathymetry model reveals that this melt rate asymmetry coincides with an asymmetry in water column thickness and that the low‐melting ice‐shelf portion is shielded from the main cavity circulation. A 2‐year record yields year‐to‐year melt rate variability of 7–9 m/a with no seasonal cycle. Our results highlight the key role of bathymetry near grounding lines for accurate modeling of ice‐shelf melt, and the importance of sustained multi‐year monitoring, especially at ice‐shelf cavities where the dominant melt rate drivers vary primarily inter‐annually. Plain Language Summary The point were the Antarctic Ice Sheet goes afloat on the ocean represents a critical region, where minor variations in melt rates can impact glacier flow and influence the rate of sea‐level rise. East Antarctica's Totten Glacier holds the potential to raise global sea level by several meters. Therefore, to understand the conditions it is exposed to, we measured melt rates for 2 years in several key locations near the point where the ice first touches the ocean. Our new measurements of the shape of the Totten Ice Shelf cavity help explain an observed spatial pattern of basal melting and together with local melt rate data resolve a disagreement between existing melt rate estimates from remote‐sensing methods. Key Points Totten Glacier melt rates vary spatially between 0 and over 20 m/a; differences are explained by water column thickness variations from updated bathymetry Temporal melt rate variability is primarily inter‐annual; melt rates differ by 7–9 m/a over two observed years and there is no clear seasonal cycle Contrary to previous findings, we find no topographic barriers to the intrusion of warm water to the Totten Glacier grounding zone

Ocean circulation around the Antarctic coastal margins plays a critical role in heat delivery to Antarctica, melting ice shelves. However, until recently, satellite‐based sea‐level observations have been limited by the presence of sea ice. With improved algorithms, it is now possible to monitor sea‐level fluctuations over most of the Southern Ocean, including sea ice‐covered areas. We identified several clockwise gyres along East Antarctic coastal margins in satellite‐derived dynamic ocean topography (DOT). Singular value decomposition analyses revealed that the coastal DOT deepening and anomalous clockwise circulation consistently occur during the positive phase of the southern annular mode (SAM), which is associated with negative wind stress curl anomalies. Shifting of the SAM to a more positive phase since the 20th century and its expected continuation into the coming century could lead to enhanced clockwise gyres along East Antarctica, contributing to increased poleward ocean heat transport. Plain Language Summary The Southern Ocean melts the Antarctic ice sheet. The poleward ocean heat, which controls ice‐ocean interactions, is transported from offshore to coastal margins across the shelf break by ocean circulation. Satellite observations are powerful for monitoring global sea‐level distribution which is closely related to ocean circulation; however, this approach is difficult to apply to polar regions with sea ice. This limitation has been addressed through the development of improved satellite algorithms, enabling monitoring in these regions. In this study, we utilized improved satellite sea‐level data to investigate the relationship between sea‐level variation and atmospheric circulation, with a focus on East Antarctic regions. Using analyses to find interlocking patterns in ocean and atmospheric variables, we found that several clockwise gyres form along the East Antarctic coastal margins along with deepening coastal sea levels during the positive phase of the Southern Annular Mode, the leading mode of the Southern Hemisphere atmospheric circulation. The negative wind stress curl tendency associated with the SAM positive phase is responsible for strengthening the regional ocean gyres. The continuous shift of the SAM to a positive phase, both in the past and near future, is expected to enhance these gyres and increase poleward ocean heat transport. Key Points Variability of the ocean circulation along East Antarctica is investigated using satellite radar altimetry Clockwise ocean circulation varies in response to the negative wind stress curl, which depends on the Southern Annular Mode Expected trend toward the positive phase of SAM will leads to enhanced poleward ocean heat transport in the East Antarctic coastal area

Assessments of the Antarctic contribution to future sea level rise have generally focused on ice loss in West Antarctica. This focus was motivated by glaciological and oceanographic observations that showed ocean warming was driving loss of ice mass from the West Antarctic Ice Sheet (WAIS). Paleoclimate studies confirmed that ice discharge from West Antarctica contributed several meters to sea level during past warm periods. On the other hand, the much larger East Antarctic Ice Sheet (EAIS) was generally considered to be relatively stable because of being largely grounded above sea level and therefore protected from ocean heat flux. However, recent studies suggest that a large part of the EAIS is grounded well below sea level and that the EAIS also retreated and contributed several meters to sea level rise during past warm periods. We use ocean observations from three ice shelf systems to illustrate the variety of ocean-ice shelf interactions taking place in East Antarctica and to discuss the potential vulnerability of East Antarctic ice shelves to ocean heat flux. The Amery and the Mertz are \"cold cavity\" ice shelves that exhibit relatively low area-averaged basal melt rates, although substantial melting and refreezing occurs beneath the large and deep Amery Ice Shelf. In contrast, new oceanographic measurements near the Totten Ice Shelf show that warm water enters the sub-ice-shelf cavity and drives rapid basal melting, as is seen in West Antarctica. Totten Glacier is of particular interest because it holds a marine-based ice volume equivalent to at least 3.5 m of global sea level rise, an amount comparable to the entire marine-based WAIS, and recent glaciological measurements show the grounded portion of Totten Glacier is thinning and the grounding line is retreating. Multiple lines of evidence support the hypothesis that parts of the EAIS are more dynamic than once thought. Given that the EAIS contains a volume of marine-based ice equivalent to 19 m of global sea level rise, the potential for ocean-driven melt to destabilize the marine-based ice sheet needs to be accounted for in assessments of future sea level rise.

Ice mass loss in the Wilkes Land sector of East Antarctica and the Amundsen and Bellingshausen Sea sectors of West Antarctica has contributed to a rise in sea levels over several decades. The massive continental ice behind the Totten Ice Shelf, equivalent to a few meters of sea-level rise, is grounded well below sea level and therefore, potentially vulnerable to oceanic heat. Here, we present analyses of comprehensive hydrographic observations at the continental slope and shelf break regions off Totten Ice Shelf. We provide robust evidence that the relatively warm Circumpolar Deep Water that originates at intermediate depths in the Antarctic Circumpolar Current is transported efficiently towards the shelf break by multiple cyclonic eddies. We propose that these semi-permanent cyclonic circulations play a critical role in transporting the available ocean heat towards Totten Ice Shelf, and melting it from underneath, thus eventually influencing the global climate.

Antarctic Bottom Water formation, which ventilates the abyssal layers of the Southern Ocean, is an integral component of the global ocean meridional overturning circulation. Considering evident freshening and density decreases in the source waters, widespread warming in the Southern Ocean suggests a weakening in the Antarctic Bottom Water supply. We demonstrate that the weakening is robust based on water mass warming in the deep and abyssal layers of the Australian-Antarctic Basin, which remained after removing the southward shift effect of the Southern Antarctic Circumpolar Current Front. Moreover, a decrease in apparent oxygen utilisation and reduced warming in the intermediate density layer below Circumpolar Deep Water extended further from the Australian-Antarctic Basin to the South Australian Basin. We suggest that a concurrent weakening in the densest portion and strengthening in the less dense portion shape the multi-basin change in the meridional overturning circulation that originates from the Southern Ocean.

Clack provides various American diplomacy links. These include \"Why Europe Is Falling Apart\" at http://www.thetower.org/article/why-europe-is-falling-apart/

Dr. [Samuel Totten]: \"The United States has avoided recognition of the Armenian Genocide for decades and continues to do so for political expediency. Instead of being a leader in recognizing the genocide as a genocide, the U.S. government continues to drag its feet. This is in direct contrast, for example, to Germany. On June 2nd, 2016, by a unanimous vote in the Bundestag, the German parliament not only acknowledged its nation's own complicity in the Armenian genocide of 1.5 million people in 1915, but called that human tragedy what it is: genocide. The Bundestag's vote should serve as a shining example to all of those nations who have yet to make a similar declaration, including the United States. In 2007 during his first presidential campaign Obama made a bold statement, but unfortunately he did not follow through: \"Two years ago, I criticized the Secretary of State for the firing of U.S. Ambassador to Armenia, John Evans, after he properly used the term 'genocide' to describe Turkey's slaughter of thousands of Armenians starting in 1915. as President I will recognize the Armenian Genocide.\" The Bundestag resolution recognizing the Armenian Genocide and its own complicity in it stands in stark contrast to U.S. silence and, ironically, denial of America's own proud record during those times. It is not too late for President Obama to rescue his reputation for integrity and the U.S.'s credibility internationally by recognizing the Armenian Genocide. It is the right thing to do, and now is the time to do it.\"

In nineteenth‐century America, strength of materials, an engineering science, focused on empirical research that yielded practical tools about how to predict the behavior of a wide variety of materials engineers might encounter as they built the nation’s infrastructure. This orientation toward “cookbook formulae” that could accommodate many different kinds of timber, stone, mortar, metals, and so on was specifically tailored for the American context, where engineers were peripatetic, materials diverse, and labor in short supply. But these methods also reflected deeper beliefs about the specialness of the landscape and the providential site of the American political experiment. As such, engineers’ appreciation of natural bounty both emerged from and contributed to larger values about exceptionalism and the practical character of Americans.