Review of WHOI Arctic Studies

1
Arctic Ocean Circulation and Climate Mary-Louise
Timmermans (WHOI)
2
September sea-ice extent from National Snow and
Ice Data Center
3
September sea-ice extent from National Snow and
Ice Data Center
4
March sea-ice extent from National Snow and Ice
Data Center
5
(No Transcript)
6
(No Transcript)
7
A complex balance of factors contributed to the
2007 ice minimum

• Unusual regional atmospheric circulation patterns
• Reduction in surface albedo allowing more solar
  heating
• of the upper ocean
• Clear skies
• Warmer Pacific- and Atlantic-origin waters

8
Autonomous Ice-Based Observatories
Sustained observations of the polar ice pack, the
overlying atmosphere, and the upper ocean water
properties.
9
Ice-Tethered Profiler (ITP)
www.whoi.edu/itp
John Toole, Rick Krishfield, Andrey Proshutinsky
(WHOI)
10
(No Transcript)
11
Ice-Tethered Profiler drift tracks
12
Current ITP locations (www.whoi.edu/itp)
Latest locations of active ITPs and annual
ice-drift vectors. NSF systems DAMOCLES AWI
AARI
13
ITPs in the Canada Basin (Beaufort Gyre)
14
Impact on ice melting
Recent large increases in bottom melting in the
Canada Basin Don Perovich (CRREL)
Ice Mass Balance buoys
15
Measurements from an Ice Mass Balance Buoy
16
Arctic Ocean Circulation
Jack Cook (WHOI)
17
The Arctic Ocean
Jayne Doucette (WHOI)
18
Warming of the Atlantic Water
Polyakov et al. 2005
19
Atlantic Water in the Canada Basin
20
Pacific Water in the central Canada Basin
21
Shallow eddies in the halocline
Aug. 2004 Nov. 2006 26 cold core
anticyclones centered between 40 and 60-m depth
22
West-East section through a typical eddy
23
West-East section through a typical eddy
24
Eddy formation region and mechanism
Temperature-Salinity of northern and southern
surface water masses
25
Surface front relatively warm fresh water to the
south and colder, saltier water to the north
North-South Section in the Canada Basin
26
A mechanism for eddy formation subduction of
water at upper ocean fronts Spall (1995)
The subducted parcel is squashed and spreads
laterally develops anticyclonic circulation for
27
Eddies

• More than 26 shallow eddies have been measured by
  ITPs.
• Eddy characteristics are consistent with their
  formation by instability of a surface front near
  800N.
• Eddies appear to have long lifetimes, with
  minimum ages between 6 and 18 months.
• The reduced stratification of the eddies may be a
  preconditioning for higher heat fluxes through
  the halocline.

How do the eddies modify the halocline energy
budget and halocline stratification so as to
impact vertical heat fluxes through the halocline?
28
A double-diffusive staircase in the Canada Basin
Map of ITP profile locations
29
Atlantic Water potential temperature maximum in
the Canada Basin
30
Typical profiles of potential temperature and
salinity in the Canada Basin
31
Potential temperature/salinity values through the
staircase across the basin
32
Map of vertical heat flux (W/m2) averaged over
the staircase
33
Map of vertical density ratio averaged over the
thermocline
34
Double-diffusive staircase

• ITP measurements reveal that Atlantic Water heat
  is transported vertically throughout the central
  Canada Basin by double-diffusion.
• Mixed layers in the staircase are shown to be
  laterally coherent for at least 800 km across the
  basin.
• Heat transport from the Atlantic Water in the
  central Canada Basin provides a small fraction of
  the total heat input to overlying waters.

35
What about the very deepest waters?
36
(No Transcript)