Decomposing the effects of ocean warming on chlorophyll a concentrations into physically and biologically driven contributions
Recently compiled observational data suggest a substantial decline in the global median chlorophyll a concentration over the 20th century, a trend that appears to be linked to ocean warming. Several modelling studies have considered changes in the ocean’s physical structure as a possible cause, whil...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2013-01-01
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| Series: | Environmental Research Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/1748-9326/8/1/014043 |
| _version_ | 1797748439925129216 |
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| author | D Olonscheck M Hofmann B Worm H J Schellnhuber |
| author_facet | D Olonscheck M Hofmann B Worm H J Schellnhuber |
| author_sort | D Olonscheck |
| collection | DOAJ |
| description | Recently compiled observational data suggest a substantial decline in the global median chlorophyll a concentration over the 20th century, a trend that appears to be linked to ocean warming. Several modelling studies have considered changes in the ocean’s physical structure as a possible cause, while experimental work supports a biological mechanism, namely an observed increase in zooplankton grazing rate that outpaces phytoplankton production at higher temperatures. Here, we present transient simulations derived from a coupled ocean general circulation and carbon cycle model forced by atmospheric fields under unabated anthropogenic global warming (IPCC SRES A1FI scenario). The simulations account for both physical and biological mechanisms, and can reproduce about one quarter of the observed chlorophyll a decline during the 20th century, when using realistically parameterized temperature sensitivity of zooplankton metabolism ( Q _10 between 2 and 4) and phytoplankton growth ( Q _10 ∼ 1.9). Therefore, we have employed and re-calibrated the standard ecosystem model which assumes a lower temperature sensitivity of zooplankton grazing ( Q _10 = 1.1049) by re-scaling phytoplankton growth rates and zooplankton grazing rates. Our model projects a global chlorophyll a decline of >50% by the end of the 21st century. While phytoplankton abundance and chlorophyll a experience pronounced negative effects, primary production and zooplankton concentrations are less sensitive to ocean warming. Although changes in physical structure play an important role, much of the simulated change in chlorophyll a and productivity is related to the uneven temperature sensitivity of the marine ecosystem. |
| first_indexed | 2024-03-12T16:04:47Z |
| format | Article |
| id | doaj.art-a016dc1c782b44b28acd9799d213584a |
| institution | Directory Open Access Journal |
| issn | 1748-9326 |
| language | English |
| last_indexed | 2024-03-12T16:04:47Z |
| publishDate | 2013-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | Environmental Research Letters |
| spelling | doaj.art-a016dc1c782b44b28acd9799d213584a2023-08-09T14:25:51ZengIOP PublishingEnvironmental Research Letters1748-93262013-01-018101404310.1088/1748-9326/8/1/014043Decomposing the effects of ocean warming on chlorophyll a concentrations into physically and biologically driven contributionsD Olonscheck0M Hofmann1B Worm2H J Schellnhuber3Potsdam Institute for Climate Impact Research , PO Box 601203, D-14412 Potsdam, Germany; Institute for Atmospheric and Climate Science, ETH Zurich , 8092 Zurich, SwitzerlandPotsdam Institute for Climate Impact Research , PO Box 601203, D-14412 Potsdam, GermanyDalhousie University , Halifax, NS, B3H 4R2, CanadaPotsdam Institute for Climate Impact Research , PO Box 601203, D-14412 Potsdam, Germany; Santa Fe Institute , Santa Fe, NM 87501, USARecently compiled observational data suggest a substantial decline in the global median chlorophyll a concentration over the 20th century, a trend that appears to be linked to ocean warming. Several modelling studies have considered changes in the ocean’s physical structure as a possible cause, while experimental work supports a biological mechanism, namely an observed increase in zooplankton grazing rate that outpaces phytoplankton production at higher temperatures. Here, we present transient simulations derived from a coupled ocean general circulation and carbon cycle model forced by atmospheric fields under unabated anthropogenic global warming (IPCC SRES A1FI scenario). The simulations account for both physical and biological mechanisms, and can reproduce about one quarter of the observed chlorophyll a decline during the 20th century, when using realistically parameterized temperature sensitivity of zooplankton metabolism ( Q _10 between 2 and 4) and phytoplankton growth ( Q _10 ∼ 1.9). Therefore, we have employed and re-calibrated the standard ecosystem model which assumes a lower temperature sensitivity of zooplankton grazing ( Q _10 = 1.1049) by re-scaling phytoplankton growth rates and zooplankton grazing rates. Our model projects a global chlorophyll a decline of >50% by the end of the 21st century. While phytoplankton abundance and chlorophyll a experience pronounced negative effects, primary production and zooplankton concentrations are less sensitive to ocean warming. Although changes in physical structure play an important role, much of the simulated change in chlorophyll a and productivity is related to the uneven temperature sensitivity of the marine ecosystem.https://doi.org/10.1088/1748-9326/8/1/01404392.20.jf92.20.jh92.20.Sgocean biogeochemistryphytoplanktoncarbon cycle |
| spellingShingle | D Olonscheck M Hofmann B Worm H J Schellnhuber Decomposing the effects of ocean warming on chlorophyll a concentrations into physically and biologically driven contributions Environmental Research Letters 92.20.jf 92.20.jh 92.20.Sg ocean biogeochemistry phytoplankton carbon cycle |
| title | Decomposing the effects of ocean warming on chlorophyll a concentrations into physically and biologically driven contributions |
| title_full | Decomposing the effects of ocean warming on chlorophyll a concentrations into physically and biologically driven contributions |
| title_fullStr | Decomposing the effects of ocean warming on chlorophyll a concentrations into physically and biologically driven contributions |
| title_full_unstemmed | Decomposing the effects of ocean warming on chlorophyll a concentrations into physically and biologically driven contributions |
| title_short | Decomposing the effects of ocean warming on chlorophyll a concentrations into physically and biologically driven contributions |
| title_sort | decomposing the effects of ocean warming on chlorophyll a concentrations into physically and biologically driven contributions |
| topic | 92.20.jf 92.20.jh 92.20.Sg ocean biogeochemistry phytoplankton carbon cycle |
| url | https://doi.org/10.1088/1748-9326/8/1/014043 |
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