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Oxygen and indicators of stress for marine life in multi-model global warming projections

Biogeosciences (2013) 10(3) 1849-1868
DOI: 10.5194/bg-10-1849-2013
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Abstract

Decadal-to-century scale trends for a range of marine environmental variables in the upper mesopelagic layer (UML, 100-600 m) are investigated using results from seven Earth System Models forced by a high greenhouse gas emission scenario. The models as a class represent the observation-based distribution of oxygen (O2) and carbon dioxide (CO2), albeit major mismatches between observation-based and simulated values remain for individual models. By year 2100 all models project an increase in SST between 2°C and 3°C, and a decrease in the pH and in the saturation state of water with respect to calcium carbonate minerals in the UML. A decrease in the total ocean inventory of dissolved oxygen by 2 % to 4 % is projected by the range of models. Projected O2 changes in the UML show a complex pattern with both increasing and decreasing trends reflecting the subtle balance of different competing factors such as circulation, production, remineralization, and temperature changes. Projected changes in the total volume of hypoxic and suboxic waters remain relatively small in all models. A widespread increase of CO2 in the UML is projected. The median of the CO2 distribution between 100 and 600m shifts from 0.1-0.2 molm-3 in year 1990 to 0.2-0.4 molm-3 in year 2100, primarily as a result of the invasion of anthropogenic ce a arbon from the atmosphere. The co-occurrence of changes in a range of environmental variables indicates the need to further investigate their synergistic impacts on marine ecosystems and Earth System feedbacks. © Author(s) 2013.

Figures

  • Fig. 2. O2 frequency distribution in the UML (from 100 to 600 m depth), obtained by sampling the volume fraction that falls within 20 mmolm−3 intervals. Black line: observation-based distribution (from GLODAP and WOA 09 gridded data). Red: 1990s modeled distribution (decadal mean). Blue: 2090s modeled distribution (decadal mean).
  • Fig. 1. Taylor diagrams: correspondence between model results (1990–1999 average) and observation-based (from GLODAP and WOA 09, annual mean) fO2 and O2 (a), fCO2, RI, and DIC (b). The polar coordinates represent the correlation coefficient R (polar angle) and the normalized standard deviation σmodel/σobs (radius). The results are relative to data between 100 and 600 m depth and are weighted by the volume of each grid cell. Observed and modeled O2 mean values and standard deviations (σ ) relative to the results of (a) are summarized in the table included in (a).
  • Table 1. Observed and modeled present-day and 2090s (decadal average) volume of three water classes identified by different O2 regimes, expressed in m3 and in percent of the total oceanic volume. In the first line, the revised WOA 05 values from Bianchi et al. (2012) are listed.
  • Fig. 3. CO2 frequency distribution in the UML (from 100 to 600 m depth), obtained by sampling the volume fraction that falls within 0.02 molm−3 intervals. Black line: observation-based distribution (from GLODAP and WOA 09 gridded data). Red: 1990s modeled distribution (decadal mean). Blue: 2090s modeled distribution (decadal mean).
  • Fig. 4. Current and projected temperature, O2, CO2, RI, pH, and A (100–600 m depth average). Observation-based fields from GLODAP and WOA 09 are shown on the left. The second column shows the projected 2090s distributions under the SRES A2 scenario, calculated as the sum of the observation-based fields and the 1990–2100 multi-model mean changes. The panels on the right represent the differences between the second and the first column. Hatched areas indicate where less than five out of seven models agree in the sign of the projected change. The contours represent the thresholds RI= 1 and A = 1.
  • Fig. 5. Changes in sea surface temperature (a), air–sea CO2 flux (b) and air–sea O2 flux (c) for the global ocean over the period 1860–2100.
  • Fig. 6. Projected changes in fO2 in the UML (100 to 600 m depth) for the SRES A2 scenario. Changes are for 2100 relative to 1870. The multi-model mean is given in the upper left panel; hatched areas indicate where less than five out of seven models agree in the sign of the projected change.
  • Fig. 8. Attribution to different drivers for changes (a) in fO2 for the global ocean and (b) in dissolved O2 for the entire Atlantic (dashed lines) and for Atlantic hypoxic waters (O2 < 50mmolm−3, solid lines). Results are from CSM1.4 and represent differences between 1870s and 2090s. Colors in panel (a) indicate total changes in fO2 (black), fO2 changes due to changes in dissolved O2 (green), in temperature (red), and in salinity (blue). Colors in panel (b) indicate total O2 changes (∆O2, black line), changes due to the air-sea O2 disequilibrium (∆O2gas, red), and to alterations in the cycling of organic matter (∆O2bio, green).

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CITATION STYLE

APA

Cocco, V., Joos, F., Steinacher, M., Frölicher, T. L., Bopp, L., Dunne, J., … Tjiputra, J. (2013). Oxygen and indicators of stress for marine life in multi-model global warming projections. Biogeosciences, 10(3), 1849–1868. https://doi.org/10.5194/bg-10-1849-2013

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