Advik Eswaran

Antarctic ice cores provide highly detailed climate histories; yet, the existing proxy record is limited by uneven spatial and temporal coverage. Collecting new ice cores will improve our understanding of climate processes in Antarctica, but the cost of drilling new records demands careful site selection. Here, we present a data-driven optimal sensor approach to select ice core sites that best constrain a chosen climate metric by iteratively applying an Ensemble Kalman Filter. We demonstrate the method by choosing two Antarctic-wide metrics: average annually resolved temperature and annual accumulation since the Industrial Era. Our approach accounts for proxy uncertainty based on the site accumulation rate; we discuss logistical constraints for specific case studies. We find that the southern Ross Ice Shelf and western Dronning Maud Land are optimal regions to reconstruct Antarctic-wide total accumulation and average temperature, respectively. We describe three case studies: 1) drilling a new core at Crary Ice Rise on the Ross Ice Shelf; 2) drilling a new core at Lyddan Ice Rise in Dronning Maud Land; and 3) redrilling the US-ITASE cores in West Antarctica. Our data-driven methodology can guide future community drilling efforts to maximize the value of new ice cores for climate reconstruction.

Antarctic ice cores provide highly detailed climate histories; yet, the existing proxy record is limited by uneven spatial and temporal coverage. Collecting new ice cores will improve our understanding of climate processes in Antarctica, but the cost of drilling new records demands careful site selection. Here, we present a data-driven optimal sensor approach to select ice core sites that best constrain a chosen climate metric, by iteratively applying an Ensemble Kalman Filter. We demonstrate the method by choosing two Antarctic-wide metrics: average annually resolved temperature and annual accumulation since the Industrial Era. Our approach accounts for proxy uncertainty based on the site accumulation rate; we discuss logistical constraints for specific case studies. We find that the southern Ross Ice Shelf and western Dronning Maud Land are optimal regions to reconstruct Antarctic-wide total accumulation and average temperature respectively. We describe three case studies: 1) drilling a new core at Crary Ice Rise on the Ross Ice Shelf; 2) drilling a new core at Lyddan Ice Rise in Dronning Maud Land; and 3) redrilling the US-ITASE cores in West Antarctica. Our data-driven methodology can guide future community drilling efforts to maximize the value of new ice cores for climate reconstruction.

Increasing Antarctic snow accumulation can mitigate sea level rise, but considerable uncertainty surrounds both past snowfall trends and future sea level projections. Here, we present a reconstruction of 19th and 20th century Antarctic accumulation, and the 20th century cumulative impact on global mean sea level. Using the Last Millenium Reanalysis framework to integrate ice core accumulation and water isotope records with a multi-model ensemble of CMIP5 climate simulations, we produce annually resolved reconstructions from 1801-2000 CE. Reconstructions demonstrate significant skill through strong satellite-era correlation with instrumental reanalysis; we find a positive Antarctic accumulation trend over the 20th century, translating to a modest amount (~1 mm) of sea level mitigation. Mitigation is primarily driven by an accelerating trend since around 1970. These findings contrast with previous 20th century mitigation estimates of ~10-12 mm; we determine that this discrepancy is due to unconstrained baseline estimates of 19th century accumulation in East Antarctica. Our results suggest that uncertainties in East Antarctic accumulation history preclude a confident estimate of Antarctic sea level mitigation, thus highlighting the need for new, high-quality accumulation records from East Antarctica.

Increasing snow accumulation over the Antarctic Ice Sheet may mitigate future sea level rise. However, current estimates of mitigation potential are poorly constrained due to limited records of past variability. We present an annually resolved reconstruction of Antarctic snow accumulation from 1801 to 2000 CE, employing a paleoclimate data assimilation methodology to integrate ice core records with a multi‐model ensemble of climate simulations. Our reconstruction correlates well with instrumental reanalysis, and we find that Antarctic accumulation rates increased over the 20th‐century, resulting in a modest amount (∼1 mm) of sea level mitigation. Mitigation is primarily driven by an accelerating trend since around 1970. Our results contrast with previous mitigation estimates of ∼10–12 mm; this discrepancy is due to poorly constrained baseline estimates of 19th‐century accumulation in East Antarctica. Our reconstruction suggests that the uncertainty of future sea level mitigation from increasing Antarctic accumulation has been underestimated.

Increasing snow accumulation over the Antarctic Ice Sheet may mitigate future sea level rise. However, current estimates of mitigation potential are poorly constrained due to limited records of past variability. We present an annually resolved reconstruction of Antarctic snow accumulation from 1801 to 2000 CE, employing a paleoclimate data assimilation methodology to integrate ice core records with a multi-model ensemble of climate simulations. Our reconstruction correlates well with instrumental reanalysis, and we find that Antarctic accumulation rates increased over the 20th-century, resulting in a modest amount (~1 mm) of sea level mitigation. Mitigation is primarily driven by an accelerating trend since around 1970. Our results contrast with a previous mitigation estimate of ~10 mm; this discrepancy is due to unconstrained baseline estimates of 19th-century accumulation in East Antarctica. Our reconstruction suggests that the uncertainty of future sea level mitigation from increasing Antarctic accumulation has been underestimated.