michael steele polar science center / apl state of the ... · polar science center / apl university...

Michael Steele Polar Science Center / APL University of Washington

March 17, 2010!State of the Arctic



“Increasing River Discharge to the Arctic Ocean” Peterson et al., Science, Dec 2002

…mostly, Russian

“20th Century Trends of Arctic Precipitation from Observational Data & a Climate Model Simulation” Kattsov & Walsh, J. Climate, 2000

….increasing

N. Hemisphere!sea ice extent!

(106 km2)

!The Intensifying Hydrologic Cycle"!(Rawlins et al. 2010)!

What about the ocean?


March 17, 2010!State of the Arctic Freshwater Content

(FWC)

Units: meters (compare w/

precip, ice melt, etc.)

Sref =!34.8!

surface

bottom

S(z)!

layer #1

layer #2

FWC ! " (Sref – S)/Sref dz!S = 34.8

0

FWF ! " " v (Sref – S)/Sref dzdx!

Units: km3/yr (compare w/

volume transport)

v x

Freshwater Flux (FWF)

!""#

!"#$%

&'(&

'#)$*

+

,(-./012 /032 /042 /052 /002

67#)$

*+

89

8/

2

/

9

2

12#

812#

:;<$=-.>( $=-.>( :;<$=-.>( $=-.>(

… getting saltier!

annual 5-yr R.M.

Steele & Ermold, 2007

“fw capacitor” Proshutinsky et al., (2002)

Polyakov et al. (2008): Downward trend # 1990s



Steele et al., 2004

It was the !atmospheric forcing!!

(i.e., winds #!ice, ocean FW release)!

Intensifying hydro cycle!was a much smaller effect!

Arctic FW & the North Atlantic Oscillation

Why did the Arctic Ocean get saltier? ! !FW release ! !FW storage

? ?

NAO -! NAO +!

Strong AC Weak

AC

Canada! Canada!

Russia! Russia!


March 17, 2010!State of the Arctic What’s new in the 2000s?

NPI moorings

helo line

EGC

Svalbard

Greenland

de Steur et al. (2010)

no FWF trend FWF

(km

3 /yr)

vol. flux below 700 m above 700 m

total: increasing, but mostly

below the FW Vo

lum

e flu

x (1

04 km

3 /yr)

-6

-12

-19

-25

-32



de Steur et al. in prep.

Fram Strait Davis

Strait

Switch Yard Lincoln

Sea

Nansen&Amundsen Basins Observational

System (NABOS) Laptev Sea

Beaufort Gyre Exploration Project

(BGEP)

Mooring array 2004-2009 Mooring array

1997-2009

Hydro survey 2000-2008 April-May

Hydro survey 2002-2008 Aug - Oct

Hydro survey 2003-2009 April-May

Hydro survey 2003-2008 Aug - Sept

Hydro survey 2000 July

Scientific Ice!Expeditions!(SCICEX) North Pole

Environmental Observatory

(NPEO)

2000s observations

Some summer, Some spring



FWC (meters)

in the 2000s

Triangles: winter/spring data

Circles: summer/fall data

Black squares: annually sampled cells

•  interior: 150 km x 150 km

•  straits: 50 km x 50 km

2000-2002 2003-2004

2005-2006 2007-2008

meters




Proshutinsky et al. (2009)


Curry et al. in prep.

Increasing!FWC some places, !but not everywhere!


FWC time series



FWC: The Pan-Arctic view from a model

Lique et al. (in prep., 2010): sea ice – ocean numerical model

2008 anomaly

meters saltier fresher

Areas of freshening, areas of salinization

! Arctic Ocean (incl. Barents Sea): anomaly ~ 0



Proshutinsky et al. (2009)


Curry et al. in prep.

Recent increase!in the Lincoln Sea!de Steur et al. in prep.

FWC time series

Lincoln Sea



FW leaking? po

tent

ial t

empe

ratu

re (°

C)

Salinity Salinity po

tent

ial t

empe

ratu

re (°

C)

Lincoln Sea (2008) Lincoln Sea (2009)

Freshening

Greenland Ellesmere Isl. Canada

Pacific Eurasian

Pacific

…consistent McPhee et al. (2009) analysis of 2008 data

Some FW from the Beaufort Gyre starting to leak out toward the North Atlantic Ocean?



Connecting outflows with FW storage?

3 to 6m increase: similar to observed!

Historical FWF Davis FWF Davis Strait FWF Fram Strait

FWC from FWF DS FWC from FWF FS Total equivalent FWC

Fram St. FWF

Davis St. FWF uncert.

uncert.

outflows

equivalent Beaufort Gyre storage change

Fram St. Davis St.

Total



Rawlins et al. 2010

Arctic Ocean (liquid) FWC !

The Longer-Term Future?

The arctic will freshen …!… but when?!!

coupled model runs



Thank! You!

michael steele polar science center / apl state of the ... · polar science center / apl university...

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