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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.


Model (CNTL)-simulated monthly mean and MODIS-Terra observed monthly composite surface concentration of chl a for June to September 2012. The white line represents satellite observed ice edge defined as 0.15 ice concentration. There are no MODIS chl a data under ice (dotted areas). MODIS chl a data are available from http://oceancolor.gsfc.nasa.gov/. Satellite ice concentration data are from http://nsidc.org/data/nsidc-0081.html.
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fig04: Model (CNTL)-simulated monthly mean and MODIS-Terra observed monthly composite surface concentration of chl a for June to September 2012. The white line represents satellite observed ice edge defined as 0.15 ice concentration. There are no MODIS chl a data under ice (dotted areas). MODIS chl a data are available from http://oceancolor.gsfc.nasa.gov/. Satellite ice concentration data are from http://nsidc.org/data/nsidc-0081.html.

Mentions: [11] To estimate the impact of the cyclone on the marine planktonic ecosystem, BIOMAS must simulate the ecosystem in the PSA with some skill. Here we compare the CNTL-simulated monthly mean surface chlorophyll a (chl a) with the Moderate Resolution Imaging Spectroradiometer (MODIS)-Terra observed monthly composite surface chl a for ice-free areas during June 2012 to September 2012 (Figure 4). Note that the basic currency of the biological model component is nitrogen (mmol N m−3), which needs to be converted to carbon (C) and chl a for model-data comparisons. We follow Lavoie et al. [2009] to use a fixed C:N (mol:mol) ratio of 106:16 [Redfield et al., 1963] and a fixed N:chl a (wt:wt) ratio of 8.75:1 for the unit conversions. The comparison shows that the model captures the basic spatial pattern of MODIS observations in the months before and after the August cyclone in the open water areas of the PSA. Model results and observations show generally higher chl a concentration in the coastal areas and on the Chukchi, Beaufort, and East Siberian shelves (Figure 4). Although model results are generally within the range of the MODIS observations in the open water areas of the PSA, the model underestimates or overestimates surface chl a from time to time and from location to location. Specifically, the model overestimates surface chl a in the open water areas of the Chukchi, East Siberian, and Laptev seas in July and August, but underestimates surface chl a in the Laptev Sea in September. The discrepancies may be linked to model overestimation or underestimation of snow/ice and nutrient distributions and to uncertainties in model parameters such as phytoplankton photoinhibition and photochemical reaction coefficients and zooplankton grazing and mortality rates [Zhang et al., 2010].


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)

Model (CNTL)-simulated monthly mean and MODIS-Terra observed monthly composite surface concentration of chl a for June to September 2012. The white line represents satellite observed ice edge defined as 0.15 ice concentration. There are no MODIS chl a data under ice (dotted areas). MODIS chl a data are available from http://oceancolor.gsfc.nasa.gov/. Satellite ice concentration data are from http://nsidc.org/data/nsidc-0081.html.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig04: Model (CNTL)-simulated monthly mean and MODIS-Terra observed monthly composite surface concentration of chl a for June to September 2012. The white line represents satellite observed ice edge defined as 0.15 ice concentration. There are no MODIS chl a data under ice (dotted areas). MODIS chl a data are available from http://oceancolor.gsfc.nasa.gov/. Satellite ice concentration data are from http://nsidc.org/data/nsidc-0081.html.
Mentions: [11] To estimate the impact of the cyclone on the marine planktonic ecosystem, BIOMAS must simulate the ecosystem in the PSA with some skill. Here we compare the CNTL-simulated monthly mean surface chlorophyll a (chl a) with the Moderate Resolution Imaging Spectroradiometer (MODIS)-Terra observed monthly composite surface chl a for ice-free areas during June 2012 to September 2012 (Figure 4). Note that the basic currency of the biological model component is nitrogen (mmol N m−3), which needs to be converted to carbon (C) and chl a for model-data comparisons. We follow Lavoie et al. [2009] to use a fixed C:N (mol:mol) ratio of 106:16 [Redfield et al., 1963] and a fixed N:chl a (wt:wt) ratio of 8.75:1 for the unit conversions. The comparison shows that the model captures the basic spatial pattern of MODIS observations in the months before and after the August cyclone in the open water areas of the PSA. Model results and observations show generally higher chl a concentration in the coastal areas and on the Chukchi, Beaufort, and East Siberian shelves (Figure 4). Although model results are generally within the range of the MODIS observations in the open water areas of the PSA, the model underestimates or overestimates surface chl a from time to time and from location to location. Specifically, the model overestimates surface chl a in the open water areas of the Chukchi, East Siberian, and Laptev seas in July and August, but underestimates surface chl a in the Laptev Sea in September. The discrepancies may be linked to model overestimation or underestimation of snow/ice and nutrient distributions and to uncertainties in model parameters such as phytoplankton photoinhibition and photochemical reaction coefficients and zooplankton grazing and mortality rates [Zhang et al., 2010].

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.