OPP-PRF: A Well-Constrained Hosing Experiment for Interrogating Arctic Precipitation Changes in the Younger Dryas

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In the next century, changes to precipitation will be among the most significant impacts of anthropogenic climate change. An important tool for predicting future climate change is understanding how climate has changed in the past. About 12,000 years ago, a significant volume of cold, fresh water was added to the North Atlantic. This fresh water is believed to have slowed the Atlantic Meridional Overturning Circulation, an ocean current that is important to the stability of the planet’s climate. Using the results of high-resolution computer simulations of iceberg paths through the ocean, this research will test the hypothesis that icebergs were the primary contributor of fresh water to the Atlantic during the Younger Dryas. This hypothesis will be tested against the idea that the fresh water was sourced from a catastrophic outburst flood on land, as well as against a more traditional, low-resolution model of fresh water forcing. These simulations will be compared to each other and to records of Arctic precipitation change during the Younger Dryas, advancing understanding of both past and present climate change in the Arctic. This research investigates the Younger Dryas, an interval of abrupt global climate change that occurred about 12,000 years ago. The Younger Dryas is believed to have been caused by the addition of cold, fresh water to the North Atlantic, which slowed Atlantic Meridional Overturning Circulation, though the exact nature of this forcing is not well understood. This work involves sensitivity experiments using an isotope-enabled global climate model, iCESM, with new constraints on the location of fresh water. The PI hypothesizes these more realistic constraints will produce a climate response more comparable to the geologic record than past works. These experiments will investigate the initiation and duration of these events in order to generate a more complete narrative of abrupt climate change in the Younger Dryas. The results of this modeling will then be compared to proxy records from Arctic lakes, interpreted through forward-modeling of the systems recording the proxies, or proxy system modeling. This approach, involving global climate modeling, proxy records, and proxy system modeling of the same event will produce a narrative of Younger Dryas climate dynamics and link those events to sediments from Arctic lakes.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.