Abstract
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 mol m−3 in year 1990 to 0.2–0.4 mol m−3 in year 2100, primarily as a result of the invasion of anthropogenic carbon 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.
Highlights
Solid EarthThe ocean is undergoing physical and chemical changes in response to climate change caused by anthropogenic emissions of gases
The Earth System Models represent the interactions between the physical climate system, biogeochemical cycles, and marine ecosystems under global warming
The models are the IPSL-CM4-LOOP model from the Institut Pierre Simon Laplace (IPSL), the MPI-ESM Earth System Model from the Max Planck Institute for Meteorology (MPIM), two versions of the Community Climate System Model (CSM1.4-carbon and CCSM3-Biogeochemical Elemental Cycling (BEC)) from the National Center for Atmospheric Research, the Bergen Climate Model (BCM-C) from the University of Bergen and Bjerknes Centre for Climate Research, the Earth System Model from the Geophysical Fluid Dynamics Laboratory in Princeton, and the UVIC2-8 as used by the Helmholtz Centre for Ocean Research Kiel (GEOMAR)
Summary
The ocean is undergoing physical and chemical changes in response to climate change caused by anthropogenic emissions of gases. These ccharabnogneTsdhiinoecxliudCdeer(CywOoid2se)spparhnedaedoretohceerangrweeanrhmoiunsge, alterations in the stratification, density structure, circulation and physical transport rates, and an increase in total carbon content by air–sea CO2 uptake forcing the ocean towards more acidic conditions and altering acid–base relationships (Bindoff et al, 2007). Oxygen (O2) and CO2 are involved in aerobic respiration where organic compounds and O2 are converted to CO2 and water. V. Cocco et al.: Oxygen and indicators of stress in multi-model projections expanding hypoxia and higher CO2 levels represent physiological stresses for marine aerobic organisms that may act synergistically with ocean acidification (Portner and Farrell, 2008)
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