Greenlandic Ice Archives of North Atlantic Common Era Climate
Matthew Osman, Ph.D., 2019
Sarah Das, Advisor
In this thesis I use modern, data-driven and physically-based modeling approaches to gain new insights into North Atlantic Common Era (A.D. 1– present) climate variability from the Greenlandic ice-core archive. First, I investigate the fidelity of ice-core glaciochemical climate proxies at the microphysical-scale, showing that several soluble species – key among them methanesulfonic acid (MSA) – undergo rapid vertical migration through a super-cooled liquid-advection process along ice grain-boundaries. I then investigate the cause of declining 19-21th-century MSA concentrations across the Greenland Ice Sheet, illuminating a 10 ± 7% climate-driven decline in marine productivity over the Industrial-era. Next, using a new climate record from a previously-unexplored ice cap in coastal west-central Greenland, I identify marked centennial-scale hydroclimate changes during the last millennium, including a ~40% increase in coastal-precipitation since the industrial-onset. Finally, leveraging a compilation of nearly 30 Greenland water-isotope records, I isolate coherent signatures of atmospheric circulation variability to reconstruct changes in the North Atlantic eddy-driven jet-stream over the last millennium, exposing progressively enhanced jet-variability during the past two-centuries consistent with amplified Arctic-driven thermal-wind forcing. This thesis thus illuminates new Common Era climatic changes, and expands the scope of the Greenlandic ice archive as proxies of the coupled North Atlantic climate system.