科研之友
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摘要
Marine biology plays an important role in the ocean carbon cycle. However, the effect of warming-induced changes in biological rates on oceanic CO2 uptake has been largely overlooked. We use an Earth system model of intermediate complexity to investigate the effect of temperature-induced changes in biological rates on oceanic uptake of atmospheric CO2 and compare it with the effects from warming-induced changes in CO2 solubility and ocean mixing and circulation. Under the representative CO2 concentration pathway RCP 8.5 and its extension, by year 2500, relative to the simulation without warming effect on the ocean carbon cycle, CO2-induced warming reduces cumulative oceanic CO2 uptake by 469PgC, of which about 20% is associated with the warming-induced change in marine biological rates. In our simulations, the bulk effect of biological-mediated changes on CO2 uptake is smaller than that mediated by changes in CO2 solubility and ocean mixing and circulation. However, warming-induced changes in individual biological rates, including phytoplankton growth, phytoplankton mortality, and detritus remineralization, are found to affect oceanic CO2 uptake by an amount greater than or comparable to that caused by changes in CO2 solubility and ocean physics. Our simulations, which include only a few temperature-dependent biological processes, demonstrate the important role of biological rates in the oceanic CO2 uptake. In reality, many more complicated biological processes are sensitive to temperature change, and their responses to warming could substantially affect oceanic uptake of atmospheric CO2. @@@ Plain Language Summary Currently, the ocean absorbs about one quarter of CO2 emitted from human activities, including fossil fuel burning and land use change. The ocean's absorption of atmospheric CO2 involves chemical, physical, and biological processes, all of which are sensitive to temperature. Here we use a coupled climate-carbon cycle model to quantify how temperature change would affect the ocean's ability to absorb atmospheric CO2. Our simulations show that warming-induced decrease in CO2 solubility and reduction in ocean ventilation cause the ocean to absorb less CO2 from the atmosphere. Furthermore, temperature change directly affects metabolic rates of marine biota, which also exerts a strong control on the ocean carbon cycle. For example, how fast phytoplankton (microscopic organisms that form the base of marine ecosystems) grow and die is sensitive to temperature; how fast detritus (dead particulate organic materials) are decomposed is also sensitive to temperature. We show that increased metabolic rates in a warmer ocean affect the ocean carbon cycle in different manners, which impacts the ocean's absorption of atmospheric CO2 to a similar extent as that caused by changes in CO2 solubility and ocean ventilation. Our study highlights the important role of temperature-dependent metabolic rates in regulating the ocean's absorption of atmospheric CO2.
- 出版日期2017-5
- 单位浙江大学
