Award: OCE-1129644

Oceans play a critical role in modulating anthropogenically-driven climate change. About 25% of carbon emissions are absorbed by oceans, in a process termed the solubility pump. Global earth system models are used to predict how this carbon sink might change over the coming century (and how it might have varied in the past). Dissolved noble gas abundances in the ocean are a useful tool for evaluating the ocean solubility pump, because their dynamics are controlled only by abiotic air-sea gas exchange processes without the complicating influence of biological production, consumption and chemical equilibration that occurs with carbon dioxide. The vast deep abyssal ocean communicates with the atmosphere only through a few unique regions of deep water formation in high northern and southern latitude regions. Using novel inverse modeling methods, we were able to tie deep ocean noble gas observations to high-latitude formation regions. We identified a significant discrepancy in the Weddell Sea in the Southern Ocean. the model was less efficient in taking up gases from the atmosphere than observations suggest. The implication of this finding is that the global model had insufficient communication between the atmosphere and ocean during deep water formation and air-sea gas exchange during formation is insufficient in the model. This information can be used to improve future ocean models and improve our understanding of future and past roles of the oceans in carbon cycling and climate. As a second principle objective was to use noble gases to constrain how bubbles from breaking waves contribute to gas exchange at the ocean surface. Certain noble gases are very sensitive to bubble processes and supersaturation of these gases provides a fingerprint of bubble-mediated exchange. This line of research supported, in part, a graduate student in the WHOI/MIT Joint Program who analyzed noble gas observations in Monterey Bay, CA to identify the best air-sea gas exchange parameterizations. Directly representing bubble-mediated exchange was determined to be essential, although some previous models were shown to overestimate the bubble influence on gas exchange. One important application of such bubble parameterizations is to enable accurate estimates of ocean net community production from ocean observing systems equipped with dissolved oxygen sensors. In addition to contributing to graduate education, project activities included active dissemination of results and underlying data and code, including archiving of results in the BCO-DMO repository, sharing of open source code on GitHub. A compilation of noble gas observations from a large number of studies will be a valuable resource for future modeling efforts. Last Modified: 12/08/2016 Submitted by: David Nicholson