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