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Abstract. The Southern Ocean is highly under-sampled for the purpose of assessing total carbon uptake and its variability. Since this region dominates the mean global ocean sink for anthropogenic carbon, understanding temporal change is critical. Underway measurements of pCO2 collected as part of the Drake Passage Time-series (DPT) program that began in 2002 inform our understanding of seasonally changing air–sea gradients in pCO2, and by inference the carbon flux in this region. Here, we utilize available pCO2 observations to evaluate how the seasonal cycle, interannual variability, and long-term trends in surface ocean pCO2 in the Drake Passage region compare to that of the broader subpolar Southern Ocean. Our results indicate that the Drake Passage is representative of the broader region in both seasonality and long-term pCO2 trends, as evident through the agreement of timing and amplitude of seasonal cycles as well as trend magnitudes both seasonally and annually. The high temporal density of sampling by the DPT is critical to constraining estimates of the seasonal cycle of surface pCO2 in this region, as winter data remain sparse in areas outside of the Drake Passage. An increase in winter data would aid in reduction of uncertainty levels. On average over the period 2002–2016, data show that carbon uptake has strengthened with annual surface ocean pCO2 trends in the Drake Passage and the broader subpolar Southern Ocean less than the global atmospheric trend. Analysis of spatial correlation shows Drake Passage pCO2 to be representative of pCO2 and its variability up to several hundred kilometers away from the region. We also compare DPT data from 2016 and 2017 to contemporaneous pCO2 estimates from autonomous biogeochemical floats deployed as part of the Southern Ocean Carbon and Climate Observations and Modeling project (SOCCOM) so as to highlight the opportunity for evaluating data collected on autonomous observational platforms. Though SOCCOM floats sparsely sample the Drake Passage region for 2016–2017 compared to the Drake Passage Time-series, their pCO2 estimates fall within the range of underway observations given the uncertainty on the estimates. Going forward, continuation of the Drake Passage Time-series will reduce uncertainties in Southern Ocean carbon uptake seasonality, variability, and trends, and provide an invaluable independent dataset for post-deployment assessment of sensors on autonomous floats. Together, these datasets will vastly increase our ability to monitor change in the ocean carbon sink.
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CESM1.2 Ocean Model Output for Eocene Including Neodymium and Oxygen Isotopes
Included are 100 years of monthly mean ocean model output from CESM1.2 integrations for the Eocene carried out by Adam Aleksinski and Matthew Huber, with critical assistance from Alexandra Jahn, and with assistance and support from Jiang Zhu (NCAR). These simulations were carried out at NCAR. These simulations incorporate results using the standard Eocene Deepmip 1 boundary conditions (Lunt et al, 2017), including the boundary condition datasets (Herold et al., 2014), and were branched off originally from simulations carried out at NCAR by Jiang Zhu (Zhu et al., 2020). The three simulations included here incorporate neodymium in them for the first time and span a range of CO2 and gateway configurations that make it appropriate for the Middle Eocene to late Eocene. The continuation (“SF_SU_55Ma_init-hycont”) experiment run continued from the end of Zhu et al. (2020)’s 3x preindustrial pCO2 (854.1 ppm) experiment, which used DeepMIP compliant geography and bathymetry for simulating the early Eocene. This simulation was run for a total of 4,800 years. Two runs each branched from this SF_SU_55Ma_init-hycont after 1,200 years of runtime, and each ran for 3,600 years after that point. In the Open Drake Passage experimental run (SF_SU_55Ma_open-hycont), the atmospheric pCO2 concentration from the continuation simulation was retained, and the bathymetry of the Drake Passage and Tasman Seaway were both lowered to a depth of 1973 mbsl. In the Halved pCO2 experiment SF_SU_55Ma_cool), the Herold et al original bathymetry was retained, but atmospheric pCO2 was reduced by a factor of half, to 427.05 ppm. The model output is global in extent and is netcdf format, which has been tarred and gzipped, and follows standard conventions for ocean GCMs. The data are on an irregular 'POP' grid. All the necessary information to read and process these data are included in the netcdf metadata.
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- Award ID(s):
- 1842059
- PAR ID:
- 10592354
- Publisher / Repository:
- U.S. Antarctic Program (USAP) Data Center
- Date Published:
- Subject(s) / Keyword(s):
- Neodymium Oxygen Isotope Ocean Circulation Model Eocene Paleoclimate Cryosphere Paleobathymetry Paleoecology Paleogeography Sharks Ocean Model Paleoproxies Paleotemperature
- Format(s):
- Medium: X
- Location:
- Antarctica
- Right(s):
- Creative Commons Attribution 4.0 International
- Sponsoring Org:
- National Science Foundation
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