ABSTRACT

626- Considerable advancements have been made toward understanding the climate forcing mechanisms and subsequent atmospheric circulation patterns that are required for the initiation of the Laurentide Ice Sheet (LIS) at the end of the last interglacial 116 thousand years (kyr B.P.) Yet, the relative importance of these forcing mechanisms, and their relationship to atmospheric variability on interannual and longer time scales, have not been determined. The Principal Investigators will undertake a comprehensive and systematic modeling investigation of the initiation and inception of the LIS over northeastern Canada, using state-of-the-art high-resolution climate and ice sheet models to determine the role of climate forcings, their influence on natural climate variability, and the impact of model resolution on the results obtained.
Objectives and Justification: The Principal Investigators will model the atmospheric state in the contemporary and last interglacial environments using the Polar MM5 regional climate model and the NCAR Community Climate System Model 2 (CCSM2). CCSM2 will produce global-scale descriptions of the atmosphere, ocean, sea-ice cover, and land surface while Polar MM5, developed specifically for high-latitudes, will yield high-resolution descriptions of the regional atmospheric circulation and surface characteristics over the likely initiation region of the LIS. From the contemporary environment, which is characterized by large interannual variability, they will identify modern analogs for glacial initiation, that is, distinct modes of atmospheric circulation that yield exceptional winter precipitation and cool summer temperatures in northeastern Canada. Data from these periods will be used in Polar MM5 simulations of several idealized modern scenarios to determine the relative importance of cool summers versus wet winters in achieving perennial snow cover. Coupled CCSM2/Polar MM5 simulations of the climate at 116 kyr B.P. will be conducted, using appropriate orbital, trace gas, and vegetation boundary conditions, to determine whether the interannual variability from the coupled climate models is sufficient to achieve glacial initiation on appropriate time scales and in the correct locations. Snapshot output from the Polar MM5 will be input to a high-resolution, three-dimensional ice sheet downscaling routine and ice sheet model for multi-millennial ice sheet simulations to determine whether the climate model snowfields are sufficient for glacial inception to occur. The location and timing of the model ice sheet will bevalidated against observed glacial geology and geomorphology in the study region. Guided by the results from the contemporary and last interglacial model simulations, specific sensitivity tests will be conducted to isolate the critical climate forcing mechanisms for glacial initiation and inception to occur at 116 kyr B.P.
Intellectual Merit and Broader Impacts: This project brings together a team of highly qualified scientists with expertise in meteorology, climate, glaciology, and glacial geology, along with sophisticated numerical models to address for the first time the explicit atmospheric processes occurring on various temporal and spatial scales that lead to glacial initiation. Coupling an explicit representation of climate to a high-resolution ice sheet model will greatly advance our understanding of the importance of climate forcing variability on ice sheet inception at both the last interglacial and the current interglacial. Because the relative roles of natural variability and anthropogenic forcing are of very important to possible future climate changes, a better understanding of climate variability at the last interglacial-glacial transition will have important implications for potential societal impacts in a future climate scenario. There will be abundant material available for educational outreach at elementary/ secondary schools, university classes, and through an interactive Internet web site. Two Ph.D. students will receive training through this research project and summer internships will be offered to inner city high school youth to develop their science skills.

Please report errors in award information by writing to: awardsearch@nsf.gov.