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Hurricane Igor Impacts on the Stratification and Phytoplankton Bloom over the Grand Banks Guoqi Han 1, Zhimin Ma 2, Nancy Chen 1 1 Northwest Atlantic Fisheries.

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Presentation on theme: "Hurricane Igor Impacts on the Stratification and Phytoplankton Bloom over the Grand Banks Guoqi Han 1, Zhimin Ma 2, Nancy Chen 1 1 Northwest Atlantic Fisheries."— Presentation transcript:

1 Hurricane Igor Impacts on the Stratification and Phytoplankton Bloom over the Grand Banks Guoqi Han 1, Zhimin Ma 2, Nancy Chen 1 1 Northwest Atlantic Fisheries Centre Fisheries and Oceans Canada 2 Memorial University of Newfoundland (Han et al., 2012) Supported by Canadian Space Agency GRIP Program

2 Hurricane Igor Track Newfoundland Pasch and Kimberlain,2010

3 Hurricane Igor

4 Objectives To examine the changes of SST, stratification and phytoplankton concentration To examine the linkage between the physical changes and phytoplankton bloom

5 Satellite SST and Chlorophyll Data  AVHRR 8-d 4-km SST from NOAA.  Merged MERIS and MODIS 8-d 4-km Chlorophyll from the ACRI-ST GlobColour Service.

6 Other Data  Buoy SST at B1 (inshore) and B2 (continental slope) from EC  T/S profiles at Station 27 off St. John’s from DFO AZMP Program

7 SST Changes SST decreased by 6 o C (adjustment time 10 h), uniform in space

8 Chlorophyll Changes Chlorophyll increased by 0.8 mg/m 3

9 Stratification Changes at Station 27 MLD (the interface depth) deepened from 18 to 60 m Deepening rate: -8.5 x 10 -4 m/s (by assuming the SST and the MLD adjustment time the same)

10 Upwelling due to Wind Stress Curl Translation speed: 60 km/h Maximum sustained wind: 35 m/s Diameter of the maximum wind: 180 km Estimated upwelling speed: 3.4x10 -4 m/s Upwelling favorable alongshore wind: 10 m/s Estimated upwelling speed: 1.4x10 -5 m/s (by assuming a horizontal scale of 100 km) Coastal Upwelling

11 Entrainment due to Wind Stirring W w at Station 27 A.MLD deepening: -8.5 x 10 -4 m/s B. Ekman pumping (W E ): 3.4x10 -4 m/s C. Coastal upwelling (W C ): 1.4 x10 -5 m/s W w =A-B-C = -12 x 10 -4 m/s Wind stirring effect is predominant.

12 Conclusions  Hurricane Igor caused an SST decrease of 6 o C over the Grand Banks.  The storm triggered an increase of 0.8 mg/m 3 in the phytoplankton concentration.  In situ measurements show a deepening of the mixed–layer depth from 18 to 60 m.  The bloom was triggered mainly by the vertical mixing due to the wind stirring effect.


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