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Complex and dynamic ocean current systems are responsible for redistributing heat and salt throughout the world’s oceans. The Gulf Stream-North Atlantic Current system plays an especially important role in moderating climate in the northern hemisphere. Changing sea surface temperatures within these systems are closely linked to climactic shifts in Earth’s history, and can influence sea level, hurricane activity, ecosystems, and weather patterns on either side of the Atlantic basin. In order to study these long-term historical changes, the shells of long-lived (300-500 years) marine bivalves that record the chemistry and other conditions of their surrounding environment can be used to reconstruct Earth’s climate history. Although such shell-based proxy records have been constructed in several regions of the world, this work will fill an important geographical gap to better understand the North Atlantic system.

Dr. Mette is working with a team of research partners to collect Arctica islandica clam shells from the coast of Norway (Vesterålen) to reconstruct sea surface temperature in a region sensitive to changes in the North Atlantic Current system. The clams will be collected from water depths of 5-30 meters by freediving and dredging from a small boat. Annual growth bands within the shells will be measured and cross dated (like tree-rings) and analyzed for oxygen isotopic composition. These data provide a combined signature of environmental conditions that will be used to reconstruct sea surface temperature and ocean circulation changes in the past.

Learn more about ocean and climate research at USGS.