ig2011_quartly_final.ppt
TRANSCRIPT
Interannual Changes in Arctic Ice-edge Blooms
Graham Quartly1 & Mahé Perrette2
1 – National Oceanography Centre (NOC), UK2 – Potsdam Institute for Climate Impact Research (PIK), Germany
Arctic Ocean: Region of change
[from Wassmannet al. (2011)
Concern about effect of reduced ice coverage
?? Impact on vitality of ecosystem
?? Effect on fish stock
?? Importance for CO2 drawdown
Arctic: A mix of different ecosystems
Seasonal ice cover in 2007
Chukchi Sea
Baffin BayBarents Sea
Three distinct marine environments:
Open water year round
Permanent ice cover
Seasonal ice cover
Outline of talk
Development of ice-edge blooms
Productivity models
Interannual variations
Schematic of bloom development
Algae underneath
the ice
Ice conc. too high
Ice-edge
bloom
Bloom fini-shed
Stratification may develop, and then open-water bloom
[From Sakshaug and Skjoldal (1989) ]
Example from Baffin Bay
Ice data from NSIDC or OSISAF (uses SSM/I)Chl data from NASA Goddard (SeaWiFS)
Bloom characteristics
50%Tim
e (y
ear
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
Marginal Ice Zone
MIZ period = any time up to 20 days after ice < 10%
Primary ProductivityPP = f ( Chl, SST, day length, PAR )
[from Perrette et al. (2011)} ]
VGPMCarrMarra et al.
Ice vs. Spring
Intensity, longevity, total contribution
VGPMCarrMarra et al
Ratio
Bloom occurrence & timing (2007)
March May July
> 20
< 0
0 - 20
< 15
> 30
Peak
Term
inati
onO
bser
vatio
ns • 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.
Interannual variability I
2005 2006 2007
Mar.AprilMayJuneJulyAug.
Year day
chlo
roph
yll (
mg.
m-3
)
First ice-free day
Bloom peak
Baffin Bay: Late melt => Weak peak (also 2004, 2008)
Interannual Variability II
1998 2001 2006
Early melt
mismatch ?
Mar.AprilMayJuneJulyAug.
Year day
chlo
roph
yll (
mg.
m-3
)
Sep.
First ice-free day
Bloom peak
Barents Sea: Early melt => Weak peak
Changes in timing
Histogram of first ice-free day
Histogram of peak lag after ice-retreat
Late blooms
Early ice retreat
MIZ periodMar. May July Sep. Open water
Barents Sea
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
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.
Changes in ice melt
Data consistency
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
SSM/I
Combining SeaWiFS, MERIS, MODIS, need to allow for:chlorophyll calibrationdata flaggingswath widthsampling time