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Interannual Changes in Arctic Ice-edge Blooms

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. Arctic Ocean: Region of change. C oncern about effect of reduced ice coverage

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Interannual Changes in Arctic Ice-edge Blooms

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  1. Interannual Changes in Arctic Ice-edge Blooms Graham Quartly1 & Mahé Perrette2 1 – National Oceanography Centre (NOC), UK 2 – Potsdam Institute for Climate Impact Research (PIK), Germany

  2. Arctic Ocean: Region of change Concern about effect of reduced ice coverage ?? Impact on vitality of ecosystem ?? Effect on fish stock ?? Importance for CO2 drawdown [from Wassmann et al. (2011)

  3. Arctic: A mix of different ecosystems Chukchi Sea Three distinct marine environments: Open water year round Permanent ice cover Seasonal ice cover Baffin Bay Barents Sea Seasonal ice cover in 2007

  4. Outline of talk Development of ice-edge blooms Productivity models Interannual variations

  5. Schematic of bloom development [From Sakshaug and Skjoldal (1989) ] Ice conc. too high Algae underneath the ice 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 Westward 3 km / day mg m-3 20 days 60 km 3 months Time (year day) 10% 50% Hovmöller diagram : transect perpendicular to the ice edge 300 km Longitude (65°W – 54°W)

  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 ) VGPM Marra et al. Carr [from Perrette et al. (2011)} ]

  10. Ice vs. Spring Intensity, longevity, total contribution

  11. Ratio VGPM Carr Marra et al

  12. Bloom occurrence & timing (2007) • 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 Observations > 20 Peak 0 - 20 < 0 > 30 Termination < 15 March Apr. May June July Aug.

  13. Interannual variability I First ice-free day Year day Aug. July June May April Mar. 2006 2007 2005 Bloom peak chlorophyll (mg.m-3) Baffin Bay: Late melt => Weak peak (also 2004, 2008)

  14. Interannual Variability II Year day First ice-free day Aug. Sep. July June May Early melt April Mar. 2001 2006 1998 Bloom peak chlorophyll (mg.m-3) mismatch ? Barents Sea: Early melt => Weak peak

  15. Changes in timing Histogram of first ice-free day Histogram of peak lag after ice-retreat Early ice retreat Late blooms MIZ period Open water Barents Sea Mar. Sep. May July

  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 CO2 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. Data consistency SSM/I Combining SeaWiFS, MERIS, MODIS, need to allow for: chlorophyll calibration data flagging swath width sampling time

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