Doctoral Dissertation Research: Cosmogenic Surface Exposure Dating of Late Holocene Spatial and Temporal Variability of the Southern Greenland Ice Sheet

Oregon State University, Corvallis OR

Investigators

Abstract

This doctoral dissertation research project will examine the behavior of the margins of the southern Greenland ice sheet during the late Holocene epoch, a time period covering the last several thousand years. The doctoral student will seek to determine whether ice margins behaved synchronously in the region and whether they reached their maximum extent before or during the time known as the Little Ice Age from about 1300 to 1900. A more precise determination of when the southern Greenland ice sheet reached its maximum extent will provide new information and insights regarding broader hemispheric climate dynamics. If the southern Greenland ice margins reached their maximum extent during the Little Ice Age at the same time as glacial margins in Europe and North America, then the southern Greenland ice sheet likely behaved in concert with a hemispheric wide climate signal. This finding would suggest that current southern Greenland ice sheet retreat might be in response to warming trends around the globe in recent centuries that are influencing ice retreat in Europe and North America. If the southern Greenland ice sheet reached its maximum before the Little Ice Age, however, a more complex set of explanations for why ice margins in different parts of the Northern Hemisphere reached their maxima during different time periods will be required. Identification of an earlier maximum also would require reconsideration of dynamics affecting the southern Greenland ice sheet itself, because its margins may stabilize in the future as climate models predict minimal warming over this part of Greenland in the coming century. Project findings will be shared more broadly with school groups and the public through education and museum programs. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career. The doctoral student will date the retreat of two southern Greenland ice sheet outlet glaciers using cosmogenic surface exposure ages on boulders from moraines that are dated as being more than 300 years in age. `These results will be compared with existing data from a pilot study and new data to the north of these locations. In the end, four different ice margins in southern Greenland will be dated, thereby allowing the testing of spatial and temporal variability in the southern Greenland ice sheet. The student will address two fundamental research questions. (1) When was the late-Holocene maximum of the southern Greenland ice sheet? Regarding this question, the student will test the hypothesis that the late-Holocene maximum underwent a late-Holocene advance more extensive than its Little Ice Age advance in response to significant early cooling. (2) Does regional climate govern southern Greenland ice sheet variability at centennial timescales? The student will address this question by testing the hypothesis that the southern Greenland ice sheet responds synchronously to centennial climate variations, such as those observed during the late Holocene. Testing these hypotheses will shed light on geologically recent ice sheet-climate interactions important for modeling the Greenland ice sheet response to spatially variable temperature changes. Project results will determine if southern GIS margins have responded to climatic changes of less than several degrees on a timescale relevant to humanity?s near-term future, a potentially transformative result, particularly for predicting sea-level rise over the coming century.