Tracking the movement and strength of the Northern Hemisphere westerlies over the last glacial cycle.

The westerly wind belts are a key part of the climate system. Knowing the strength and position of the westerlies during different climate states and across abrupt shifts in climate would provide insight into the mechanisms of climate variability. Studying the westerlies during past warm intervals is particularly important because modern observations of weather patterns suggest that the westerly winds are moving poleward in response to global warming. The proposed study will document the strength and position of the Northern Hemisphere westerlies using sediment records of dust accumulation and upper ocean biological productivity. Sediment cores from sites in the North Pacific Ocean will cover the last 150,000 years. They will include the most recent global warm interval roughly 130,000 to 115,000 years ago. The Broader Impacts of the proposed study include support for a postdoctoral fellow. The study also will provide opportunities for including high school students in hands-on research through the Lamont High school Intern Program. That program builds on existing partnerships with New York City and Rockland County high schools to recruit students from groups underrepresented in the earth sciences.

This proposed study will produce five ~150 kyr dust, productivity, and grain size records from the North Pacific Ocean to characterize the westerly winds during various mean climate states (peak interglacials of MIS 5e and the Holocene as well as peak glacials of MIS 6 and the last glacial maximum), and how they respond to abrupt climate changes during Terminations I and II. These records will use samples from five marine sediment cores from a recent RV Sonne research cruise to the North Pacific (SO264) that encompass ~15° latitude. These data will fill a gap in the current picture of a key region in the Northern Hemisphere and will serve as benchmarks for modeling studies. These datasets will be useful to both the paleoclimate and modern/future climate modeling fields, as they will provide constraints on the natural variability of the westerlies to changes in potential driving mechanisms such as ice volume and atmospheric temperature gradients, thus aiding essential modeling of future changes in the westerly winds. Finally, the results of this work could serve as the impetus to perform similar studies in other regions of the world, such as the Southern Hemisphere, allowing questions related to hemispheric synchroneity of atmospheric circulation across various climate regimes to be addressed. The PI is the co-chair of the new Lamont LDEI Task Force and is deeply involved in implementing diversity programs on all levels, including active recruitment of underrepresented minorities in the Geosciences. Interpretations and conclusions drawn from this work will be brought to the public via non-technical settings such as the annual Lamont-Doherty Open House.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.