Holocene records of submerged peats constrain sea level models for Eastern North America

Since the early 1900s, scallop fisherman trawling along the shores of Long Island have noted peat deposits under the Atlantic Ocean (1). These deposits are records of submerged land and contain tree trunks and mammoth teeth (2). Previous work (3) shows that the submerged peat can be up to 12,000 years old. Though these deposits provide a valuable record of past environmental changes and help create models of how and at what rates local sea level has changed, there has not been extensive research on these deposits since the 1970s. Understanding sea level change in the Northeast is especially important due to its high population affected by future sea level rise. New sediment cores collected by the Bureau of Ocean and Energy Management (BOEM) in this region reveal peat deposits buried under 2-3m of sand and clay 15km off shore Long Island in the Atlantic Ocean (3) and provide the opportunity to investigate a unique pattern of environmental change. We use a variety of techniques to characterize these changes and look for evidence of past storms and sea level change, including: AMS macrofossil radiocarbon dating, sedimentological analysis, palynology, macrofossil analysis and loss on ignition (LOI).

Preliminary results from macrofossils and a very high organic content indicate that the peat deposits formed in a terrestrial environment. The cores are currently at 24.2m water depth, therefore, sea level has risen at least that amount since they formed. This information is crucial for constraining and understanding all the variables that impact sea level change. Since the last glacial maximum (~20,000 ka), when the Laurentide Ice Sheet melted, the land in Canada has been uplifting while the coastal US is sinking. This process, glacial isostatic adjustment (GIA) has major implications for forecasting future sea level change in the Northeastern US (4). Our results from the BOEM cores provide important new constraints for North American and Atlantic GIA estimates and will improve sea level models for North America and Europe's sea level rise over the next several hundred years.

Emery + (1967)

Whitmore + (1967)

BOEM, OCS Study Report 2012-008

Rovere + (2016)