ASTE (former NOSE):An Arctic subpolar gyre State Estimate(NSF-funded)

Patrick Heimbach, An T. Nguyen, Ayan Chaudhuri, Gael Forget, Rui M. Ponte, and Carl Wunsch

MIT & AER

Estimating the Circulation and Climate of the Oceanhttp://ecco-group.org

Hurricane Sandy on Oct 28, 2012 …

Rationale

• Produce a regional eddy-permitting state estimate focused on:– Arctic ocean– North Atlantic, especially subpolar gyre

• Special emphasis on:– Arctic sea ice-ocean interactions– a dynamically consistent Arctic hydrography– understanding of the planned subpolar gyre

mooring array (OSNAP)– Arctic-subarctic exchanges– Subpolar-subtropical exchanges

ECCO-Production v4 grid: LLC_90

ASTE grid: LLC_270

ASTE domain

ECCO v4residualmisfit toin-situobs.

Take openboundariesfromgloballyoptimizedsolution

Observations: collecting dedicated hydrography in the Nordic Seas

observation instrument product/source area period dT

Mean dynamic topography (MDT)

• GRACE SM004-GRACE3• GRACE GGM02• EGM2008/DNSC07

CLS/GFZ (A.M. Rio)CSR/U. Texas (B. Tapley)N. Pavlis

global time-mean mean

Sea level anomaly (SLA)

• TOPEX/POSEIDON•Jason-1/2• ERS-1/2, ENVISAT• GFO

NOAA/RADS & PO.DAACNOAA/RADS & PO.DAACNOAA/RADS & PO.DAACNOAA/RADS & PO.DAAC

65oN/S65oN/S82oN/S65oN/S

1993 – 20022002 – 20111992 – 20112001 - 2008

dailydailydailydaily

bottom pressure • EIGEN-GRACE05 GFZ Potsdam global 2002 – 2011 weekly

SST • blended, AVHRR (O/I)• TRMM/TMI• AMSR-E (MODIS/Aqua)

Reynolds & SmithGHRSSTGHRSST

Global40oN/SGlobal

1992 - 20111998 - 20042001 - 2011

monthlydailydaily

SSS Various in-situ WOA09 surface Global climatology monthly

In-situ T, S(floats, sections,…)

• Argo, P-Alace• XBT• CTD• SEaOS

IfremerD. Behringer (NCEP)variousSMRU & BAS (UK)

“global”“gobal”sectionsSO

1992 – 2011 1992 – 2011 1992 – 2011 2004 – 2010

dailydailydailydaily

Mooring arrays •TOGA/TAO, Pirata• Florida Straits

PMEL/NOAANOAA/AOML

TropicsN. Atl.

1992 – 20111992 – 2011

dailydaily

Climatological T,S • WOA09• OCCA

WOA09Forget, 2010

“global”“global”

1950 - 20081950 - 2002

meanmean

sea ice cover • satellite brightness temp. (passive microwave)

• NSIDC-0079 (Bootstrap)• NSIDC-0051 (NASA

Team)

Arctic, SO 1992 - 2011 daily

Wind stress QuickSCAT • NASA (Bourassa)• SCOW (Risien & Chelton)

global 1999 – 2009climatology

dailymonthly

Tide gauge SSH Tide gauges NBDC/NOAA sparse 1992 - 2006 monthly

Flux constraints from ERA-Interim, JRA-25, NCEP, CORE-2 variances

Various global 1992 - 2011 2-day to14-day

Balance constraints heat & freshwater (E-P-R) global 1992 - 2011 mean

bathymetry Smith & Sandwell, ETOPO5 global - -

Atmospheric forcing uncertainties

Chaudhuri et al., submitted 2012:A comparison of atmospheric re-analysis products for the Arctic Ocean and implications for uncertainties in air-sea fluxes

Sea ice model development

• Improved sea ice thermodynamics– now conserves properties– supposedly more stable adjoint– easier term-by-term budget

• new sea ice tracer capabilities– first use is simulation of sea ice age to enable split

into first-year (FY) vs. multi-year (MY) sea ice (Pierre Rampal, now at Nansen Center, Bergen)

• implementation of Ice Thickness Distribution (ITD) scheme (Torge Martin, now at APL, UW)

• sea ice dynamics: JFNK solver (Martin Losch) see tomorrow’s session

Initial sample results from improved sea ice model:Simulation and observation of multi-year sea ice fraction

Rampal et al., in preparation

Initial sample results from improved sea ice model:Simulation of the decline of multi-year sea ice fraction

Rampal et al., in preparation

Outlook – see also An Nguyen’s talk on Thursday

• Next steps:– initial optimization of global parameters, especially in

relation to forcing fields– switch from JRA25 to ERA-Interim?– test of adjoint system, especially sea ice

thermodynamics– assessment of an “iter. 0” estimate– perform initial optimization

• Long-term outlook:– Establish feedback loop between global LLC90 (ECCO

v4) and regional LLC270 (ASTE);– Put into global LLC270 context– Develop higher-resolution nestings from optimized

solution