How does sea level change affect marine life? This is one intriguing question Expedition 381 is exploring. We know sea level rises and falls around 120 meters (~400 feet) every time the planet alternates between glacial and interglacial periods. Scientists use the term glacial to describe intervals when the Northern Hemisphere had large ice sheets extending well into Canada, United States, and much of Europe. As ice built up it took water from the ocean lowering the average sea level of the planet. The Gulf of Corinth is an ideal location to study the rise and fall of sea level because the entrance (Rion sill) is only 61 meters below sea level. Therefore, the Gulf of Corinth was sometimes connected to the Mediterranean and at other times it was an isolated lake!
Of course, seawater and lakes have very different animals and plants. Also, oceans have distinctive chemistry compared to freshwater. These differences will cause changes in the geology which we can observe in the drilled cores. Many of the records we are collecting show these variations clearly! As we drill in different locations and measure different aspects of the sediment and pore water, we learn the fine details of these processes.
As all fun science however, the more we learn the more questions we create!
Main image: Simone Sauer and Patrizia Geprägs collecting methane samples. Courtesy of DSmith@ECORD/IODP