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Abstract The southeastern Atlantic Ocean is a crucial yet understudied region for the ocean absorption of anthropogenic carbon (Canth). Data from the A12 (2020) and A13.5 (2010) cruises offer an opportunity to examine changes in dissolved inorganic carbon (DIC), its stable isotope (δ13C), and Canthover the past decade within a limited region (1∼3°E, 32∼42°S). For the decade of 2010–2020, Canthinvasion was observed from the sea surface down to 1,200 m based on both DIC and δ13C data. The mean Canthincrease rate (1.08 ± 0.26 mol m−2 yr−1) during this period accelerated from 0.87 ± 0.05 mol m−2 yr−1during the previous period (1983/84–2010). The δ13C‐based Canthincrease closely matches the DIC‐based estimation below 500 m but is 26% higher in the upper ocean. This discrepancy is likely due to δ13C's longer air‐sea exchange timescale, seasonal variability in the upper ocean, and the chosen ratio of anthropogenically induced changes in δ13C and DIC. Finally, column inventory changes based on the two methods also exhibit very similar mean Canthuptake rates. The paired DIC concentration and stable isotope dataset may enhance our ability to constrain Canthaccumulation and its controlling mechanisms in the ocean.
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The Combined Effects of Ocean Acidification and Respiration on Habitat Suitability for Marine Calcifiers Along the West Coast of North America
Abstract The California Current Ecosystem (CCE) is a natural laboratory for studying the chemical and ecological impacts of ocean acidification. Biogeochemical variability in the region is due primarily to wind‐driven near‐shore upwelling of cold waters that are rich in re‐mineralized carbon and poor in oxygen. The coastal regions are exposed to surface waters with increasing concentrations of anthropogenic CO2(Canth) from exchanges with the atmosphere and the shoreward transport and mixing of upwelled water. The upwelling drives intense cycling of organic matter that is created through photosynthesis in the surface ocean and degraded through biological respiration in subsurface habitats. We used an extended multiple linear‐regression approach to determine the spatial and temporal concentrations of Canthand respired carbon (Cbio) in the CCE based on cruise data from 2007, 2011, 2012, 2013, 2016, and 2021. Over the region, the Canthaccumulation rate increased from 0.8 ± 0.1 μmol kg−1 yr−1in the northern latitudes to 1.1 ± 0.1 μmol kg−1 yr−1further south. The rates decreased to values of about ∼0.3 μmol kg−1 yr−1at depths near 300 m. These accumulation rates at the surface correspond to total pH decreases that averaged about 0.002 yr‐1; whereas, decreases in aragonite saturation state ranged from 0.006 to 0.011 yr‐1. The impact of the Canthuptake was to decrease the amount of oxygen consumption required to cross critical biological thresholds (i.e., calcification, dissolution) for marine calcifiers and are significantly lower in the recent cruises than in the pre‐industrial period because of the addition of Canth.
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- Award ID(s):
- 2023545
- PAR ID:
- 10500225
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 129
- Issue:
- 4
- ISSN:
- 2169-9275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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