Arctic Freshwater update Cube 43 Alan Condron

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Arctic Freshwater updateCube 43Alan Condron
Peter Winsor 20th February
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Original Questions Asked

• How well does the ECCO2 model represent the
  Arctic? Is it realistic?
• A recent paper by Serreze et al. presented an
  observed freshwater budget for the Arctic. How
  well can the model reproduce this?
• Over time the model Arctic becomes increasingly
  salty (reduced volume of freshwater). Why is
  this?

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There is a rapid reduction in the amount of
freshwater as the arctic becomes saltier and
losses its vertical stratification
Cube 22
Cube 43
Vertically integrated freshwater
Start to lose Beaufort gyre circulation
After 30 years
1992
2002
Time
Total freshwater 67552 km3
Total freshwater 74714 km3
Total freshwater 32000 km3
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Changes in freshwater volume over time
Observed 74345 km3
Cube 22
Cube 43 (blue) and 47 (red)
A longer simulation might be useful in resolving
the initial decline in freshwater volume?
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Towards an improved arctic freshwater budget for
the cube runs

• Consider transports of water, ice and salt
  in/out of the model Arctic via Fram Strait,
  Bering Strait, Canadian Archipelago, Barents Sea
  etc, with the aim of identifying why the cube
  runs are becoming saltier.

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Arctic gates
Bering Strait
Amundsen Sea
MClure Strait
Canadian Archipelago
Queen Elizabeth Islands
Nares Strait
Barents Sea
Fram Strait
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Examples
Fram Strait
Fram Strait
Bering Strait
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Volume transports (monthly data)
Fahrbach et al., Woodgateet al, Schauer et
al., Rudels et al.,
Observational time series exist for this period
to allow model comparison.
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Liquid freshwater transport (Ft)(monthly output
cube 43)
Importing Freshwater
FT U (1-(sal/34.8) where U is volume
transport. Note that positive and negative FT are
considered
Exporting Freshwater
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Sea Ice freshwater transport (monthly cube 43)
Rothrock et al., Prinsenberg et al.
Main ice export via Fram Strait. Export through
Canadian Archipelago is primarily in liquid form.
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Total (ice water) Freshwater Transport (anomaly
from 1992-2001 av.)
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Arctic freshwater is leaving via the Canadian
Archipelago
Total (Ice water) freshwater transport
anomalies (from 1992-2001 av.)
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A closer look at the Canadian ArchipelagoIce
water freshwater transport
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NAO and Freshwater Transport
Correlation NAO-total freshwater r -0.25
NAO-Can. Arch. r -0.16
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Towards an Arctic basin freshwater budget
ATMOSPHERE
ATMOSPHERE
Precip 3253
Precip 3253
Evap1299
Evap1299
OCEAN OUT 8874 IN
8591 Imbalance -283
OCEAN OUT 10372 IN
9494 Imbalance -878
Bering 2263 (-150)
LAND Run-off
LAND Run-off
Bering 2489
R 3000
R 3000
Barents Sea 398 (58)
Barents Sea 340
Canadian Arch. (Water) 2174 (-976)
Canadian Arch. (Water) 3153
Canadian Arch. (Ice) 8
Canadian Arch. (Ice) 158
Barents (Ice) 104
Fram Strait (water) 2405
Fram Strait (water) 2555 (150)
Fram Strait (ice) 2265
Fram Strait (ice) 2336 (71)
Cube 43
From Serreze et al. (in press)
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Where to from here.

• Establish why freshwater is exported through the
  Canadian Archipelago. Is it a response to 1990s
  wind forcing (strong NAO) and loss of Beaufort
  gyre freshwater?
• Examine cube 47 - more realistic river run-off
  from P.Winsor
• Consider P-E from NCEP.
• Compare model overflows in 1990s to observational
  time series data (Fram and Bering data covering
  model run period).

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