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Tue June 4, 2013
Dr. Dorothy Peteet, Columbia University – Hudson River and Climate Records
In today’s Academic Minute, Dr. Dorothy Peteet of Columbia University reveals what the Hudson River has to say about the climate of the past.
Dorothy Peteet is a research scientist at Columbia University’s Lamont-Doherty Earth Observatory and the NASA Goddard Institute for Space Studies. Her research interests include paleoclimate, paleoecology, climate modeling, wetland carbon storage, and palynology. Peteet uses sediment cores to analyze pollen, spores, and plant and animal macrofossils to assess abrupt climate change and patterns of droughts, floods, warm intervals, and recent coolings such as the Little Ice Age.
Dr. Dorothy Peteet – Hudson River and Climate Records
Major droughts are rare in recent New York memory. But sediments built up in marshes and lakebeds over centuries can tell us about climate in the more distant past.
My colleagues and I explore the Hudson River’s many marshes, from New York City to wilder sites farther north. We use canoes, rubber boots and big hollow augers, to pull up plugs of layered mud. Back in the lab, we sift through and extract pollen, spores and seeds. Counting the abundance of different types at different times with the microscope tells us what past forests were like—and, by extension, what the climate was like. For instance, oaks and hemlocks, common today, require a lot of moisture; other trees, such as pines and hickories, tend to live in drier times.
The cores indicate that several “megadroughts” have occurred in the last 6,000 years. The longest one lasted 500 years, from 850 to 1350 AD. As less rain fell, the flow of the Hudson River ebbed, and salt water from the sea moved further upriver. A salty signature stays in the sediment. Forest fires raged, as indicated by a thick layer of charcoal from this time. This happened during the so-called Medieval Warm period--a time when grape pollen shows up in arctic ice cores, and when now long-gone Viking settlements on Greenland basked in warmth. That gives us evidence that this drought was connected to widespread higher temperatures at that time.
The last major New York drought occurred from 1961 to 1963. Back then, the water supply of New York City went from full to one quarter of capacity, in just two years. If history repeats itself, New York’s now much larger population would be severely affected.
How can we better prepare ourselves? One way is to determine how often severe droughts have happened—and why. This will help us to predict them, and to prepare for the climate of the future.
Production support for the Academic Minute comes from Newman’s Own, giving all profits to charity and pursuing the common good for over 30 years, and from Mount Holyoke College.