IG2011_Quartly_final.ppt

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IG2011_Quartly_final.ppt

  1. 1. Interannual Changes in Arctic Ice-edge Blooms Graham Quartly 1 & Mahé Perrette 2 1 – National Oceanography Centre (NOC), UK 2 – Potsdam Institute for Climate Impact Research (PIK), Germany
  2. 2. Arctic Ocean: Region of change [from Wassmann et al. (2011) C oncern about effect of reduced ice coverage ?? Impact on vitality of ecosystem ?? Effect on fish stock ?? Importance for CO 2 drawdown
  3. 3. Arctic: A mix of different ecosystems Three distinct marine environments: Open water year round Permanent ice cover Seasonal ice cover Seasonal ice cover in 2007 Chukchi Sea Baffin Bay Barents Sea
  4. 4. Outline of talk Development of ice-edge blooms Productivity models Interannual variations
  5. 5. Schematic of bloom development [From Sakshaug and Skjoldal (1989) ] Algae underneath the ice Ice conc. too high Ice-edge bloom Bloom fini-shed Stratification may develop, and then open-water bloom
  6. 6. Example from Baffin Bay Ice data from NSIDC or OSISAF (uses SSM/I) Chl data from NASA Goddard (SeaWiFS)
  7. 7. Bloom characteristics 50% Time (year day) Longitude (65°W – 54°W) 10% 20 days Westward 3 km / day 60 km 300 km 3 months mg m -3 Hovmöller diagram : transect perpendicular to the ice edge
  8. 8. Marginal Ice Zone MIZ period = any time up to 20 days after ice < 10%
  9. 9. Primary Productivity PP = f ( Chl, SST, day length, PAR ) [from Perrette et al. (2011)} ] VGPM Carr Marra et al.
  10. 10. Ice vs. Spring Intensity, longevity, total contribution
  11. 11. Ratio VGPM Carr Marra et al
  12. 12. Bloom occurrence & timing (2007) March May July > 20 < 0 0 - 20 < 15 > 30 <ul><li>Most observations in June – August </li></ul><ul><li>90% of adequately observed pixels experience chl > 0.5 mg.m -3 , and 70% > 1 mg.m -3 </li></ul><ul><li>Blooms take place later as the season advances (and as the MIZ moves futher North) </li></ul><ul><li>overall 50 % of blooms > 0.5 mg.m -3 are over within 30 days </li></ul>Apr. June Aug. Peak Termination Observations
  13. 13. Interannual variability I Year day chlorophyll (mg.m -3 ) First ice-free day Bloom peak Baffin Bay: Late melt => Weak peak (also 2004, 2008) 2005 2006 2007 Mar. April May June July Aug.
  14. 14. Interannual Variability II Early melt mismatch ? Year day chlorophyll (mg.m -3 ) Sep. First ice-free day Bloom peak Barents Sea: Early melt => Weak peak 1998 2001 2006 Mar. April May June July Aug.
  15. 15. Changes in timing Histogram of first ice-free day Histogram of peak lag after ice-retreat Late blooms Early ice retreat MIZ period Open water Barents Sea Mar. May July Sep.
  16. 16. Implications <ul><li>Large changes in melt date affects intensity of ice-edge bloom </li></ul><ul><li>Ecosystem may lose dual-bloom nature </li></ul><ul><li>Highly variable effects on other trophic levels </li></ul><ul><li>?? Effects on total productivity and CO 2 drawdown </li></ul>
  17. 17. Summary <ul><li>Ice-edge bloom is an important ecological niche (bloom within 20 days of ice-melt occurs in ~90% of seasonal ice zone) </li></ul><ul><li>Growth and productivty dependent upon timing (likely different response for different regions) </li></ul><ul><li>Early ice-melt may affect other trophic levels </li></ul>Perrette, M. et al. (2011), Near-ubiquity of ice-edge blooms in the Arctic, Biogeosciences , 8, 515–524.
  18. 18. Changes in ice melt
  19. 20. Data consistency SSM/I Combining SeaWiFS, MERIS, MODIS, need to allow for: chlorophyll calibration data flagging swath width sampling time 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Pixel SEAWIFS 9 km MERGED 9 km MODIS 9 km NSIDC 25 km OSISAF 10 km

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