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IG2011_Quartly_final.ppt

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  • 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. 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. 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. Outline of talk Development of ice-edge blooms Productivity models Interannual variations
  • 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. Example from Baffin Bay Ice data from NSIDC or OSISAF (uses SSM/I) Chl data from NASA Goddard (SeaWiFS)
  • 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. Marginal Ice Zone MIZ period = any time up to 20 days after ice < 10%
  • 9. Primary Productivity PP = f ( Chl, SST, day length, PAR ) [from Perrette et al. (2011)} ] VGPM Carr Marra et al.
  • 10. Ice vs. Spring Intensity, longevity, total contribution
  • 11. Ratio VGPM Carr Marra et al
  • 12. Bloom occurrence & timing (2007) March May July > 20 < 0 0 - 20 < 15 > 30
    • Most observations in June – August
    • 90% of adequately observed pixels experience chl > 0.5 mg.m -3 , and 70% > 1 mg.m -3
    • Blooms take place later as the season advances (and as the MIZ moves futher North)
    • overall 50 % of blooms > 0.5 mg.m -3 are over within 30 days
    Apr. June Aug. Peak Termination Observations
  • 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. 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. 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. Implications
    • Large changes in melt date affects intensity of ice-edge bloom
    • Ecosystem may lose dual-bloom nature
    • Highly variable effects on other trophic levels
    • ?? Effects on total productivity and CO 2 drawdown
  • 17. Summary
    • Ice-edge bloom is an important ecological niche (bloom within 20 days of ice-melt occurs in ~90% of seasonal ice zone)
    • Growth and productivty dependent upon timing (likely different response for different regions)
    • Early ice-melt may affect other trophic levels
    Perrette, M. et al. (2011), Near-ubiquity of ice-edge blooms in the Arctic, Biogeosciences , 8, 515–524.
  • 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