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The great 2012 Arctic Ocean summer cyclone enhanced biological productivity on the shelves.

Zhang J, Ashjian C, Campbell R, Hill V, Spitz YH, Steele M - J Geophys Res Oceans (2014)

Bottom Line: In the central PSA, however, model simulations indicate a decrease in PP and plankton biomass.The simulated biological gain on the shelves is greater than the loss in the central PSA, and therefore, the production on average over the entire PSA is increased by the cyclone.The generally positive impact of cyclones on the marine ecosystem in the Arctic, particularly on the shelves, is likely to grow with increasing summer cyclone activity if the Arctic continues to warm and the ice cover continues to shrink.

View Article: PubMed Central - PubMed

Affiliation: Applied Physics Laboratory, University of Washington Seattle, Washington, USA.

ABSTRACT

[1] A coupled biophysical model is used to examine the impact of the great Arctic cyclone of early August 2012 on the marine planktonic ecosystem in the Pacific sector of the Arctic Ocean (PSA). Model results indicate that the cyclone influences the marine planktonic ecosystem by enhancing productivity on the shelves of the Chukchi, East Siberian, and Laptev seas during the storm. Although the cyclone's passage in the PSA lasted only a few days, the simulated biological effects on the shelves last 1 month or longer. At some locations on the shelves, primary productivity (PP) increases by up to 90% and phytoplankton biomass by up to 40% in the wake of the cyclone. The increase in zooplankton biomass is up to 18% on 31 August and remains 10% on 15 September, more than 1 month after the storm. In the central PSA, however, model simulations indicate a decrease in PP and plankton biomass. The biological gain on the shelves and loss in the central PSA are linked to two factors. (1) The cyclone enhances mixing in the upper ocean, which increases nutrient availability in the surface waters of the shelves; enhanced mixing in the central PSA does not increase productivity because nutrients there are mostly depleted through summer draw down by the time of the cyclone's passage. (2) The cyclone also induces divergence, resulting from the cyclone's low-pressure system that drives cyclonic sea ice and upper ocean circulation, which transports more plankton biomass onto the shelves from the central PSA. The simulated biological gain on the shelves is greater than the loss in the central PSA, and therefore, the production on average over the entire PSA is increased by the cyclone. Because the gain on the shelves is offset by the loss in the central PSA, the average increase over the entire PSA is moderate and lasts only about 10 days. The generally positive impact of cyclones on the marine ecosystem in the Arctic, particularly on the shelves, is likely to grow with increasing summer cyclone activity if the Arctic continues to warm and the ice cover continues to shrink.

No MeSH data available.


Simulated difference in the convergence of (a–d) ocean velocity Uo, (e–h) phytoplankton, and (i–l) zooplankton in the upper 100 m of the Arctic Ocean between the CNTL and SENS runs over the period 5–11 August 2012, where u is ocean velocity vector, P and Z are phytoplankton and zooplankton concentrations, and z is depth. The CTNL-simulated convergence fields of these variables are generally close to the difference fields in magnitude and spatial pattern and are therefore not shown.
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fig09: Simulated difference in the convergence of (a–d) ocean velocity Uo, (e–h) phytoplankton, and (i–l) zooplankton in the upper 100 m of the Arctic Ocean between the CNTL and SENS runs over the period 5–11 August 2012, where u is ocean velocity vector, P and Z are phytoplankton and zooplankton concentrations, and z is depth. The CTNL-simulated convergence fields of these variables are generally close to the difference fields in magnitude and spatial pattern and are therefore not shown.

Mentions: [19] The simulated spatial patterns of the storm-induced change in nitrate concentration in the upper 100 m show a decrease over most of the shelves because of increases in PP there (Figures 6a–6d), which draws down nutrients, including those that are mixed upward from the lower portion of the water column. (The water column is often less than 100 m over the shelves.) As mentioned earlier, it is the higher nitrate concentrations in the surface waters (Figures 7a–7d) that fuel this increase in PP, while at the same time the total nitrate in the upper 100 m is drawn down and incorporated into increased phytoplankton biomass (Figures 6f–6i). The spatial patterns also show an increase in simulated nitrate concentration in the upper 100 m in the central PSA where the storm was centered (Figures 7f–7h). This is because the cyclone results in a strong cyclonic surface ocean circulation (Figures 8a–8c), which leads to strong divergence in the central PSA and corresponding convergence in the adjacent areas, including some of the shelf regions (Figures 9a–9c). The elevated divergence in the central PSA, often dominated by Ekman convergence and downwelling when there are no cyclones, likely causes upwelling in that region, leading to an increase in nitrate concentration over the upper 100 m (Figures 7f–7h), but not as shallow as the upper 10 m (Figures 7a–7d). This explains the low phytoplankton growth/PP during the storm in the central PSA (Figures 6a–6d).


The great 2012 Arctic Ocean summer cyclone enhanced biological productivity on the shelves.

Zhang J, Ashjian C, Campbell R, Hill V, Spitz YH, Steele M - J Geophys Res Oceans (2014)

Simulated difference in the convergence of (a–d) ocean velocity Uo, (e–h) phytoplankton, and (i–l) zooplankton in the upper 100 m of the Arctic Ocean between the CNTL and SENS runs over the period 5–11 August 2012, where u is ocean velocity vector, P and Z are phytoplankton and zooplankton concentrations, and z is depth. The CTNL-simulated convergence fields of these variables are generally close to the difference fields in magnitude and spatial pattern and are therefore not shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508965&req=5

fig09: Simulated difference in the convergence of (a–d) ocean velocity Uo, (e–h) phytoplankton, and (i–l) zooplankton in the upper 100 m of the Arctic Ocean between the CNTL and SENS runs over the period 5–11 August 2012, where u is ocean velocity vector, P and Z are phytoplankton and zooplankton concentrations, and z is depth. The CTNL-simulated convergence fields of these variables are generally close to the difference fields in magnitude and spatial pattern and are therefore not shown.
Mentions: [19] The simulated spatial patterns of the storm-induced change in nitrate concentration in the upper 100 m show a decrease over most of the shelves because of increases in PP there (Figures 6a–6d), which draws down nutrients, including those that are mixed upward from the lower portion of the water column. (The water column is often less than 100 m over the shelves.) As mentioned earlier, it is the higher nitrate concentrations in the surface waters (Figures 7a–7d) that fuel this increase in PP, while at the same time the total nitrate in the upper 100 m is drawn down and incorporated into increased phytoplankton biomass (Figures 6f–6i). The spatial patterns also show an increase in simulated nitrate concentration in the upper 100 m in the central PSA where the storm was centered (Figures 7f–7h). This is because the cyclone results in a strong cyclonic surface ocean circulation (Figures 8a–8c), which leads to strong divergence in the central PSA and corresponding convergence in the adjacent areas, including some of the shelf regions (Figures 9a–9c). The elevated divergence in the central PSA, often dominated by Ekman convergence and downwelling when there are no cyclones, likely causes upwelling in that region, leading to an increase in nitrate concentration over the upper 100 m (Figures 7f–7h), but not as shallow as the upper 10 m (Figures 7a–7d). This explains the low phytoplankton growth/PP during the storm in the central PSA (Figures 6a–6d).

Bottom Line: In the central PSA, however, model simulations indicate a decrease in PP and plankton biomass.The simulated biological gain on the shelves is greater than the loss in the central PSA, and therefore, the production on average over the entire PSA is increased by the cyclone.The generally positive impact of cyclones on the marine ecosystem in the Arctic, particularly on the shelves, is likely to grow with increasing summer cyclone activity if the Arctic continues to warm and the ice cover continues to shrink.

View Article: PubMed Central - PubMed

Affiliation: Applied Physics Laboratory, University of Washington Seattle, Washington, USA.

ABSTRACT

[1] A coupled biophysical model is used to examine the impact of the great Arctic cyclone of early August 2012 on the marine planktonic ecosystem in the Pacific sector of the Arctic Ocean (PSA). Model results indicate that the cyclone influences the marine planktonic ecosystem by enhancing productivity on the shelves of the Chukchi, East Siberian, and Laptev seas during the storm. Although the cyclone's passage in the PSA lasted only a few days, the simulated biological effects on the shelves last 1 month or longer. At some locations on the shelves, primary productivity (PP) increases by up to 90% and phytoplankton biomass by up to 40% in the wake of the cyclone. The increase in zooplankton biomass is up to 18% on 31 August and remains 10% on 15 September, more than 1 month after the storm. In the central PSA, however, model simulations indicate a decrease in PP and plankton biomass. The biological gain on the shelves and loss in the central PSA are linked to two factors. (1) The cyclone enhances mixing in the upper ocean, which increases nutrient availability in the surface waters of the shelves; enhanced mixing in the central PSA does not increase productivity because nutrients there are mostly depleted through summer draw down by the time of the cyclone's passage. (2) The cyclone also induces divergence, resulting from the cyclone's low-pressure system that drives cyclonic sea ice and upper ocean circulation, which transports more plankton biomass onto the shelves from the central PSA. The simulated biological gain on the shelves is greater than the loss in the central PSA, and therefore, the production on average over the entire PSA is increased by the cyclone. Because the gain on the shelves is offset by the loss in the central PSA, the average increase over the entire PSA is moderate and lasts only about 10 days. The generally positive impact of cyclones on the marine ecosystem in the Arctic, particularly on the shelves, is likely to grow with increasing summer cyclone activity if the Arctic continues to warm and the ice cover continues to shrink.

No MeSH data available.