Abstract: The mismatch between oceanic proxy data and climate model results over the past millennia has been a long-lasting challenge. Although both are valuable sources of paleoclimate information, there is a strong discrepancy in variance between models and proxies, so that they cannot be compared directly. In addition, local sea-surface temperature (SST) reconstructions are often inconsistent among proxy types. We first performed several offline data assimilation experiments with different standardized SST proxy datasets using the climate models LOVECLIM and CESM in order to investigate the effect of proxy selection on local and regional reconstructions over the Common Era (0-2000 AD). All experiments work technically at the local scale, but the spatial pattern of the reconstruction varies with the type(s), number and density of proxies, and, where there is no proxy, the choice of the model. We then developed empirical scaling factors based on independent SST observations to correct for the discrepancy between model and proxy amplitude. While it is essential to scale proxies, scaling the model leads to complications because of the biases in the sea ice extent. Data assimilation of scaled proxies results in coherent SST reconstructions at the scale of the North Atlantic, with timing and amplitude that are in agreement with those given by forced models.
Dr Neil Ross from Newcastle University will be giving us a lecture on the 20th of November in ELA 102a (from 1pm-2pm) as part of our Departmental Seminar Series.
Title: Basal boundary conditions, ice flow and subglacial hydrology of Foundation Ice Stream and Academy Glacier, Antarctica
Abstract: The Foundation Ice Stream-Academy Glacier complex is a major Antarctic outlet, with a potential sea level contribution of ~3 m. The bed of the Foundation Ice Stream trunk is ~2 km below sea level, whilst the Academy Glacier is underlain by a major East Antarctic marine basin, the Pensacola-Pole Basin, with potential for unstable grounding line retreat. Until very recently (i.e. Bedmap2), our understanding and characterisation of this major Antarctic catchment was limited, with few ice-penetrating radar measurements, so little was known about how subglacial topography and basal conditions may influence the ice flow and glaciology of Foundation Ice Stream and Academy Glacier. Using data from recent aerogeophysical campaigns (i.e. NASA’s Operation IceBridge and ESA’s PolarGap), we report: (a) large-scale topographic and geological constraints on the onset of enhanced ice flow beneath the upper Foundation Ice Stream and upper Academy Glacier; (b) the subglacial hydrology and active subglacial lakes of the ice stream catchment; and (c) basal conditions, subglacial hydrology and ice-ocean interactions of the trunk and grounding zone of Foundation Ice Stream. The implications of these investigations, and future research opportunities, for the Foundation Ice Stream-Academy Glacier complex will be outlined.