A journey through time
In order to turn these salt marsh cores into a figure that shows age and sea level, the sediment is first sliced up by centimeter. Then, it is analyzed for age using an isotope detector for the last 150 years, and radiocarbon dating for layers older than that.
Once the age of the sediment is known at each depth, the researchers need to determine where sea level was when it was at the top of the marsh. To do that, portions of the same sections are spread over microscope plates so the foraminifera—single-celled organisms often referred to as forams—can be counted.
In salt marshes, forams make a shell by gluing pieces of sediment to themselves. Different species favor different depths in a marsh, and can show whether a sample of sediment is from a high portion of a marsh or directly at sea level.
A boot in both worlds
While field science and modeling are often carried out by separate scientists, Kelly McKeon (above), a doctoral student in the MIT-WHOI Joint Program, aims to do both.
The science party on Prince Edward Island was composed of people who work across the whole range of disciplines in reconstructing past sea level.
“I gained a lot of new connections,” McKeon says, “I have field experience, but not in sea-level reconstructions. The reason I am working with Chris is to learn how to do sea-level modeling. Before this trip he was the only person I knew in that space.”
McKeon sees modeling as a key to gathering better salt marsh samples. “Numerical models can help predict what we should see in field data and validate the observations we make there.”