International Workshop Explores Seafloor Pockmarks and Their Role in Earth’s Carbon Cycle

MARUM-co-organized workshop focuses on Seafloor pockmarks and their role in modulating the release of geological carbon through glacial cycles

What role do so-called pockmarks on the ocean floor play? This was the topic of a workshop focusing on the pockmarks off the coast of New Zealand. The workshop was supported by the U.S. Science Support Program (USSSP) and the International Ocean Drilling Programme (IODP³) and jointly organized by researchers from New Zealand, the USA and Bremen.

Around 30 researchers took part in the workshop in Corpus Christi (USA) to draw up proposals for marine drilling and associated site investigations. With this workshop, the organizers aim to launch a comprehensive scientific programme designed to shed light on the extent to which geological mechanisms influence CO₂ concentrations in the atmosphere during glacial and interglacial periods.

These research aims directly contribute to the overarching goals and investigation strategies of the Cluster of Excellence ‘The Ocean Floor – Earth's Uncharted Interface’ hosted by MARUM – Center for Marine Environmental Sciences, University of Bremen

The term ‘pockmark’ refers to characteristic craters on the seabed that form when liquids or gases escape from the subsurface. They are found worldwide in many bodies of water, from lakes, rivers and estuaries to coastal waters and the deep sea. In clay-rich sediments and where there is little influence from currents and waves, they sometimes persist for many centuries and bear witness to past gas emissions.

A vast area of the seafloor on the Chatham Rise east of New Zealand is covered by crater-like pockmarks. Sub-bottom profiler data show clear evidence that these pockmarks formed repeatedly around glacial-stage maxima. Large radiocarbon excursions observed in sediment cores suggest that the pockmarks formed by release of geologic carbon-rich fluids at the end of the last glacial period.

These observations support a novel hypothesis that pockmark formation modulated the release of geologic carbon to the ocean and thereby contributed to increased atmospheric CO2 concentrations during deglaciations. Validation of this hypothesis would be a paradigm shift from the prevailing hypothesis that does not incorporate geologic processes to explain atmospheric CO2 variations.

The workshop as well as the drilling proposal is coordinated by Ingo Pecher (Texas A&M University Corpus Christi, USA), Lowell Stott (University of Southern California, USA), Lorna Strachan (University of Auckland, New Zealand) and Ewa Burwicz-Galerne (MARUM – Center for Marine Environmental Sciences, University of Bremen).