The National Science Foundation awarded $601,729 to Aaron Putnam, associate professor at the School of Earth and Climate Sciences; Brenda Hall, professor at the School of Earth and Climate Sciences and Climate Change Institute; and Katherine Allen, assistant professor at the School of Earth and Climate Sciences, for research looking at how glaciers’ seasonal fluctuations may have caused drastic climate changes.
The period of rapid transition from full-glacial conditions to warmer interglacial conditions at the end of the last ice age featured drastic climate changes in the North Atlantic region, the origins of which are still a matter of debate. It is generally thought that these climate changes involved large fluxes of glacial icebergs and meltwater interfering with the circulation of the North Atlantic Ocean. However, the North Atlantic region paradoxically appears to have been at its coldest during periods of increased glacial melt.
One hypothesis, developed by UMaine professor George Denton, suggests that these rapid transitions were highly seasonal in nature, with summertime warming driving glacial melt that formed a freshwater lid over the North Atlantic that could freeze over every winter and lead to dramatic coolings during the winter season. Understanding how winters and summers evolved is therefore important for diagnosing the causes of abrupt climate change — and understanding how the North Atlantic seasonal cycle responds to enhanced summer warming and glacial melt today.
“Glaciers are incredibly sensitive, purely physical monitors of the temperature of the atmosphere. By studying their history imprinted on the landscape and captured in offshore sediments in the Gulf of Maine, we can gain unique insights into the abrupt climate events that punctuated the last great global warming that ended the ice age” Putnam says.
The team’s project, entitled “P2C2: Collaborative Research: The Role of Seasonality in Abrupt Climate Change — a Test by Reconstructing Fluctuations of a Late-Glacial Ice Mass in Eastern North America,” will look at whether the summertime warming that caused glaciers to recede and melt into the Atlantic Ocean set in motion a chain of events that led to bitterly cold winters soon after.
To do so, Putnam and his team of researchers will track the retreat of a glacial ice mass that was once in northwestern Maine through geological dating of glacial landforms, called moraines, that formed alongside the receding ice front. Together with collaborator Thomas Lowell from the University of Cincinnati they will employ isotopic methods, known as beryllum-10 surface-exposure dating and radiocarbon dating, to develop a chronology of ice retreat in north-central Maine. They will also use marine geochemistry to understand when and how glacial melt impacted the Gulf of Maine. With this two-pronged approach, the scientists hope to determine whether the ice cap melted and introduced freshwater into the Gulf of Maine during the iconic winter-centric cold snaps of the last termination. If the team’s observations align with predictions, it would dovetail with the pattern of surface-freshening previously found in North Atlantic ocean sediments — and support the seasonality hypothesis of abrupt climate change.
“Microfossils preserved on the seafloor are the key to unlocking ocean history during this pivotal event. Our team will explore land-sea connections by comparing clues from the Gulf of Maine and clues from the land, providing a new view that synthesizes both terrestrial and marine perspectives,” Allen says.
Ultimately, in collaboration with climate scientist Joellen Russell at the University of Arizona, the study aims to provide a data-model test of the seasonality hypothesis for abrupt climate change, and to further the understanding of the history of global glacial patterns. The project will provide field-based training and education for emerging scientists. The researchers will also work closely with the Baxter Park Authority on informing the public about the glacial and climatic history of the region and its greater global context by developing a 3D-printed educational landscape model and an informative smartphone app that can be used throughout the park.
“The landscape of Maine tells a fascinating tale of how glacial ice behaved as the last ice age was coming to an end. We hope to work with our colleagues at Baxter State Park to make this remarkable glacial history accessible to the general public,” Putnam says.
The award starts Sept. 1. The full award for the project, including funds awarded to collaborators — Lowell at the University of Cincinnati and Russell at the University of Arizona, totals nearly $1 million.
