CEOSCEOSCEOS

Sea ice, hydrological, and biological processes in the Churchill River estuary region,

Hudson Bay

Freshwater Institute, Fisheries & Oceans Canada, Winnipeg, MBCentre for Earth Observation Science, University of Manitoba

Institute of Ocean Sciences, Fisheries & Oceans Canada, Sidney, BCUniversity of Calgary Centre for Alpine and Arctic

Climate Research

Z.A. Kuzyk, R.W. Macdonald, M.A. Granskog, R.K. Scharien, R.J. Galley, C. Michel, D. Barber, and G. Stern

Introduction

Chesterfield Inlet

Nelson R.

Haye

s R.

Sever

n R.

Wini

skR.

Thelon R.

Kazan R.

Tha-anne R.Thlewiaza R.

Churchill R.

Seal R.

Grande Riviere de la Baleine

Nastapoca R.

Innuksuac R.

Povingnituk R.

Hudson Bay

La Grande R.

• Estuaries– Near-shore regions

where river water and sea water meet

– Prominent features of Hudson Bay

• Interface for transfer– River water– Heat– Dissolved and

particulate materials• Affect how and when

materials delivered and may alter properties.

• Potential sites of biological production.

Lepage and Ingram 1988

Great Whale River

Ingram and Prinsenberg, 1998

La Grande and Eastmain

• Ice cover alters the character of estuaries.– Prevents direct wind and

wave mixing– Sometimes allows larger

plumes• Sea ice complicates

the freshwater budget.– Melt –freshwater source– Grows - salt (brine)

• Western Hudson Bay• Winter-spring transition

– March to May 2005

• Data sources• Hydrological and meteorological

data– Environment Canada, Manitoba

Hydro• Physical observations of ice cover• Measurements of salinity, oxygen

isotopes (δ18O), nutrients and suspended particulate material

• Simple models of ice growth• Budgets for heat and freshwater

Churchill River Estuary Region

EstuaryButton Bay (marine site)

(b) MODIS image, Jan 1, 2005

Landfast ice

Mobile ice offshore

Flaw leadRubble ice

Landfast ice, lead in the distance

Rubble ice at outer edge of landfast ice

WINTER PRE-MELT

EARLYMELT FRESHET

BREAK UP

Winter

Pre-melt

Early melt

Freshet

Break up

PERIOD

0

1

2

3

Chl

orop

hyll

a(m

g m

-3)

EstuaryButton Bay

River

Changes in Surface Water Chlorophyll a Concentrations

0 10 20 30 40SALINITY

0

1

2

3

4

5

6

Nitr

ate

(uM

)

Salinity0 10 20 30 40

0

10

20

30

40

50

Salinity

Early melt & freshetWinter & pre-melt

Changes in Nutrient Distributions

Sili

cic

acid

(uM

)Seawater

River water

Conceptual Model: Physical Evolution of Estuary

Churchill River Discharge

Over-flooding of river water along edge of rubble zone

Button Bay

Breach in rubble and gap in landfast ice

Quickbird RGB Composite, May 27, 2005

Great Whale River• Stable, wide landfast ice cover and

large plume• Smooth gradients in salinity and

nutrients• Phytoplankton distributed along

gradients

Nelson River• Narrow, unstable landfast ice

cover if any at all• Well mixed, probably nutrient

rich• Plume flowing directly into

lead

Contrast with other Estuaries in Hudson Bay

CEOSCEOSCEOS

Conclusions and Implications• Wide spectrum of conditions for frozen

estuaries– Highly variable seasonally– Dependent on sea ice and river discharge– Inter-annual variability?– Variability and potentially instability may

pose challenge for predicting sensitivity and responses of estuaries to change.

CEOSCEOSCEOS

Conclusions and Implications• Freshwater budget allows estimate of region’s

sea ice growth.– Water column in Button Bay reflects more

ice growth than can be accounted for in the landfast ice

• Influence of ice growth in flaw lead, maybe polynya in NW• Comparison with satellite observations• Modelling context

– Ice growth as source of cold, saline bottom water for all of Hudson Bay

– In Arctic Ocean, estuary structure and distribution of river water are important controls on this process.

CEOSCEOSCEOS

Acknowledgements• ArcticNet• Fisheries and Oceans (FWI and IOS)• Churchill Northern Studies Centre, Port of

Churchill, community of Churchill• North/South Consultants Inc., Manitoba Hydro,

Environment Canada• Natural Sciences and Engineering Research

Council of Canada (NSERC)• Northern Scientific Training Program (Indian

and Northern Affairs)• Academy of Finland• Field team including M. Pazerniuk, A. Hare,

E. Braekevelt, J. Ehn, R. Hodgson, B. LeBlanc, P. Fitzpatrick, R. Bougie, J. Batstone