THE ARCTIC
BASINS
AN INTEGRATED PHYSICAL AND BIOLOGICAL
PERSPECTIVE
BA Bluhm1, KK Kosobokova2, EC Carmack3
1University
of Tromsø, 2Department of Fisheries and
Oceans Canada, 3P.P. Shirshov Institute of Oceanology
Moscow
Currents, Fronts and Life
Basis: Pan-Arctic
Workshop 2012
• “Overarching perspectives
Advection
Productivity
Arctic
Ocean
Microbial
loop
of contemporary and future
ecosystems in the Arctic
Ocean”
• Realization of strong
connectivity on pan-Arctic
scale
• PiO 2015
Change
The challenge
• Ice retreat: basins now
exposed to light and wind in
summer
• Change in what we thought
we knew about shelf-basin
exchange and air-sea
interaction
• Changes in physics and
advection will alter
production, diversity,
response, and resilience to
anthropogenic forcing
A Wake-Up Call to the Deep Arctic Basins
• Economic opportunities
related to sea ice decline
brought the Arctic Basins
onto the global map
• Territorial claims
• Oil and gas, shipping,
fisheries?
High connectivity to the global ocean
• Estuarine circulation forced by low salinity and density
waters entering from Pacific, encountering more saline
denser waters entering from Atlantic
Data from World Ocean Data Base
Surface circulation
• Wind-driven surface
circulation forces the
Trans-Polar Drift from
Siberia to Fram Strait,
and the Beaufort Gyre
in the Canada Basin
Data from World Ocean Data Base
Halocline sources, flows and front
• Waters of Pacific and
Atlantic origin that are
modified during passage
over shelves
• Particle and biota inputs
• Two mater mass
assemblies (± Pacific
Water) with distinct
chemical (nutrient)
properties
• Frontal boundary
between domains is
Atl/Pac halocline front
After McLaughlin et al. 1996
Arctic Circumpolar Boundary Current from
Atlantic water inflows
• topographic
ally-trapped
Arctic
Circumpolar
Boundary
Current
• carries AW
into all
basins
• leaving Atl.
footprint in
biota
CB
NB
After Aksenov et al. 2011, Rudels et al. 2013
Data from JOIS
Arctic Ocean Deep and Bottom water
• Sources in both the Nordic
Seas and Arctic Ocean
explain faunal
connections to today’s N
Atl. Fauna
• Slow exchange of Arctic
Ocean Deep Waters
(Isolation ages: EB 250 yrs,
AB 400 yrs) with complex
recirculation
After Aagarad et al. 1985
Deep exchanges
• Similar faunal communities below ridge sill depths
(but benthic fauna poorly known)
• Dispersion mechanisms unclear
Deep-water
benthos
Data from Bluhm et al. 2011, Kosobokova et al. 2011
Deep-water
zooplankton
Oligotrophic basins
Nitrate
• Surface nutrient
concentrations low
(esp. AB) despite
high concentration
at depth
• Winter reset
essentially absent
• marked basin
differences in
nutrients result in
PP differences (?)
• Stratification limits
primary production
Surface
200 m
Silicate
Surface
200 m
Data from World Ocean Data Base
Advection delivers carbon / biota
• Import of
carbon, food
and grazers
through
advected
expatriates
• Greater faunal
abundance
associated
with larger
inflows in EB
Zooplankton
expatriates
Data from Kosobokova 2012, Kosobokova et al. 2011
In situ and advected carbon supply
• A “Carbon Belt” around
basin perimeter, in inflow
areas, near surface
Vertical zooplankton biomass distribution
North
of 85°N
inflow
Data from Bluhm et al. 2011
Data from Kosobokova and Hirche (2009), Kosobokova and Hopcroft (2010),
Kosobokova (2012)
What’s changing: basin to shelf change - Sea ice
retreat implies enhanced shelf break upwelling
• Retreating ice beyond the shelf break will enhance shelf-break
upwelling and increase onshelf transport of basin water
• This can enhance productivity and draw corrosive waters on
the shelf
Canada Basin
Beaufort Sea
Amundsen Gulf
Corrosive
layer
Aragonite concentration
Tremblay et al. 2011
Yamamoto—Kawai et al. 2013
What’s changing: Shelf to basin exchange
associated with increased hydrological cycle
Benthic Consumer Tissue δ13C (‰)
• Terrestrial
0
carbon
(riverine,
permafrost)
affects food
web down
slope
• Consequen
ces of
increased
river runoff?
-28
-26
-24
-22
-20
-18
500
1000
500
1000
0
500
1000
0
Beaufort Sea
500
1000
L. Bell, K. Iken, B. Bluhm, MSc thesis
Bottom Depth (m)
0
Summary ...
Amerasian Basin
Eurasian Basin
• Surface
water
• Halocline
• Atlantic
layer
• Deep/
bottom
water
T/S of Polar mixed layer
Halocline stratification
T/S of Atlantic layer
T/S of deep water
Isolation age of bottom water
River discharge (8 largest rivers)
Subarctic inflow (Sv)
Amerasian Basin
fresher
Multiple, stronger
colder
colder
older
Smaller (21%)
Pacific water, ~1
Eurasian Basin
saltier
Simple, weaker
warmer
warmer
old
Larger (65%)
Atl water, ~5-8
Summary ...
Amerasian Basin
Nutrient concentrations surface
Nutrient concentrations deep
Primary production (g C m-2 yr-1)
Shelf-break upwelling
Zooplankton biomass (upper water
column)
Benthic biomass
Biogeographic connectivity
(exc. surface zoopl. expatriates)
Community structure similarity
Common feeding types (deep)
Eurasian Basin
Amerasian Basin
lower
Mod-high
lower
present
low
Eurasian Basin
low
lower
low
present
higher
Low
With Atlantic
low
With Atlantic
Weak horizontally - strong vertically
Detritus feeders, predators,
microbial loop
Detritus feeders, predators,
microbial loop (susp.
feeders)
Thanks
• Arctic Frontiers for invitation
• Those whose work this review is based on
• Pan-Arctic Croatia Workshop organizers, ARCTOS
• P Kimber, L Xie, F Huettmann, M Kaufman, F
Grabowska technical support