When
Where
Available in person in Harshbarger 110 and via zoom (see email for link)
Abstract
Climate models predict that anthropogenic warming should weaken the meridional tropical Pacific Walker Circulation as differential increases in precipitation and specific humidity reduce the vertical mass flux in the atmosphere. Such a weakening has not been detected in observations, however, potentially reflecting a combination of model biases and/or the influence of internal variability and sea surface temperature patterns. Instrumental observations of the Walker Circulation are also quite limited, preventing a long-term perspective on its range of variability and response to radiative forcing. Here, we use offline paleoclimate data assimilation and isotope-enabled climate model simulations to reconstruct the Walker Circulation during the last millennium. We evaluate a range of climate fields and circulation indices as reconstruction targets, and we test the sensitivity of the assimilation to the selection of paleoclimate proxies used in the analysis. These results can be used to place current Walker Circulation variability in a multi-centennial context, but highlight the challenges and sensitivities to the choice of methods and data employed in the assimilation process.
Bio
Kevin Anchukaitis is a Professor of Earth Systems Geography in the School of Geography, Development, and Environment, as well as the Laboratory of Tree-Ring Research at the University of Arizona. He is a climate scientist, paleoclimatologist, and dendrochronologist specializing in identifying, understanding, and interpreting forced and unforced variability in the climate system on timescales from individual extreme events to long-term trends. His work also investigates the dynamic response of socio-ecological systems to climate and environmental change.