Epibenthic Foraminifera Porosity in the Florida Straits: Implications for Downcore Bottom Water Oxygen Records
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Stevens, William Mark
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Under the current emission scenario, oceans are expected to warm significantly by 2100. A likely result of such warming is decreased ocean circulation and subsequent deoxygenation, especially in the interior ocean. Ocean deoxygenation results in biodiversity loss and lower fishery yields, incentivizing the prevention of additional warming. Future climate predictions are necessary to develop warming-reducing policies; however, the extent to which changes in ocean circulation affect changes in oxygenation are not well understood. In this study, we investigate the ability of a recently developed paleoclimate proxy which uses the percent pore area, or porosity, on epibenthic foraminifera tests to reconstruct bottom water oxygen (BWO) in the Florida Straits, a region well known for capturing changes in global thermohaline strength. We analyzed the porosity of 49 Planulina spp. across the Late Holocene portion of 7 sediment cores in the Florida Straits and found a mean porosity of 4.7%. We argue that the porosity proxy is unreliable at reconstructing BWO changes in well oxygenated regions but that an updated semi-quantitative threshold may be useful in mid-oxygen regions. Considering previous hypotheses of oxygenation in the Florida Straits during the Last Glacial Maximum and Younger Dryas, we advise against the use of the porosity proxy for a Florida Straits downcore record and instead encourage further use of the proxy in low-mid oxygen regions in the ocean such as the Eastern Equatorial Pacific to better understand how circulation changes affect interior ocean oxygen.
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