ABSTRACT. The spatial pattern of accumulation rate can be inferred from internal layers in glaciers and ice sheets. Non-dimensional analysis determines where finite strain can be neglected ('shallow-layer approximation') or approximated with a local one-dimensional flow model ('local-layer approximation'), and where gradients in strain rate along particle paths must be included ('deep layers'). We develop a general geophysical inverse procedure to infer the spatial pattern of accumulation rate along a steady-state flowband, using measured topography of the ice-sheet surface, bed and a 'deep layer'. A variety of thermomechanical ice-flow models can be used in the forward problem to calculate surface topography and ice velocity, which are used to calculate particle paths and internal-layer shapes. An objective tolerance criterion prevents over-fitting the data. After making site-specific simplifications in the thermomechanical flow algorithm, we find the accumulation rate along a flowband through Taylor Mouth, a flank site on Taylor Dome, Antarctica, using a layer at approximately 100 m depth, or 20% of the ice thickness. Accumulation rate correlates with ice-surface curvature. At this site, gradients along flow paths critically impact inference of both the accumulation pattern, and the depth-age relation in a 100 m core.

The most recent glacial to interglacial transition constitutes a remarkable natural experiment for learning how Earth's climate responds to various forcings, including a rise in atmospheric CO 2 . This transition has left a direct thermal remnant in the polar ice sheets, where the exceptional purity and continual accumulation of ice permit analyses not possible in other settings. For Antarctica, the deglacial warming has previously been constrained only by the water isotopic composition in ice cores, without an absolute thermometric assessment of the isotopes' sensitivity to temperature. To overcome this limitation, we measured temperatures in a deep borehole and analyzed them together with ice-core data to reconstruct the surface temperature history of West Antarctica. The deglacial warming was 11.3 ± 1.8 • C, approximately two to three times the global average, in agreement with theoretical expectations for Antarctic amplification of planetary temperature changes. Consistent with evidence from glacier retreat in Southern Hemisphere mountain ranges, the Antarctic warming was mostly completed by 15 kyBP, several millennia earlier than in the Northern Hemisphere. These results constrain the role of variable oceanic heat transport between hemispheres during deglaciation and quantitatively bound the direct influence of global climate forcings on Antarctic temperature. Although climate models perform well on average in this context, some recent syntheses of deglacial climate history have underestimated Antarctic warming and the models with lowest sensitivity can be discounted.climate | paleoclimate | Antarctica | glaciology | temperature F rom the Last Glacial Maximum (LGM) around 21 ka to the middle of the Holocene, increased greenhouse gas concentrations and reduced reflectivities of the surface and atmosphere directly increased the uptake of energy to Earth's climate system by about 7W·m −2 (1-3) and warmed the surface by 3-6 • C on average (4-7). Although contributing little to this global average because of the comparatively small area involved, the warming in polar regions holds particular interest. In addition to driving changes of ice sheets, permafrost, and hydrology and modulating oceanic and atmospheric circulations, polar warming partly controlled both the evolution of surface reflectivity and the transfer of carbon dioxide from ocean to atmosphere and hence the climate forcing itself. Further, reconstructions of polar warming during deglaciation permit quantification of one key prediction of climate theory-that feedback processes amplify temperature changes in polar regions relative to the global average (4, 8, 9), a phenomenon referred to as polar amplification. Arctic data reveal a warming three to four times the global average based on a wide variety of indicators (6), including combined analyses of ice-core data and borehole temperatures (10, 11). Limited available constraints suggest a smaller but still amplified Antarctic warming, roughly 1.5 to 2.5 times greater than the global average (6, 12). T...

The Antarctic contribution to sea level is a balance between ice loss along the margin and accumulation in the interior. Accumulation records for the past few decades are noisy and show inconsistent relationships with temperature. We investigate the relationship between accumulation and temperature for the past 31 ka using high‐resolution records from the West Antarctic Ice Sheet (WAIS) Divide ice core in West Antarctica. Although the glacial‐interglacial increases result in high correlation and moderate sensitivity for the full record, the relationship shows considerable variability through time with high correlation and high sensitivity for the 0–8 ka period but no correlation for the 8–15 ka period. This contrasts with a general circulation model simulation which shows homogeneous sensitivities between temperature and accumulation across the entire time period. These results suggest that variations in atmospheric circulation are an important driver of Antarctic accumulation but they are not adequately captured in model simulations. Model‐based projections of future Antarctic accumulation, and its impact on sea level, should be treated with caution.