AOMIP workshop #12 Jan 14-16, 2009 WHOI Improved modeling of the Arctic halocline with a sub-grid-scale brine rejection parameterization Nguyen, An T., D. Menemenlis, R. Kwok, submitted to JGR Oceans

AOMIP workshop #12 Jan 14-16, 2009 WHOI AOMIP results [Holloway, 2007]

AOMIP workshop #12 Jan 14-16, 2009 WHOI Previous Works Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m Duffy et al. [1997, 1999] in the Southern Ocean: Antarctic Intermediate Water

AOMIP workshop #12 Jan 14-16, 2009 WHOI Previous Works z b [Smith and Morison, 1998][Helfrich, 1994]

AOMIP workshop #12 Jan 14-16, 2009 WHOI Brine Rejection Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m  Sea-ice retains 33% of salt  67% of salt rejected back to the ocean  Rejected salt s(z) is distributed down to bottom of mixed layer z=D according to: A: constant of normalization n, D: parameters to be determined

AOMIP workshop #12 Jan 14-16, 2009 WHOI Brine Rejection Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m Density structure :  d  /dz in mixed layer: to kg/m 3 /m  d  top of halocline ~ to kg/m 3 /m 04 Feb 1992

AOMIP workshop #12 Jan 14-16, 2009 WHOI MITgcm Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m ECCO2: High- Resolution Global- Ocean and Sea-Ice Model Ocean model: ~ 18km horizontal, 50 vertical levels volume-conserving, C-grid Surface BC’s: ECMWF / ERA-40 based Initial conditions: optimized bathymetry: GEBCO KPP mixing [Large et al., 1994] Sea ice model: C-grid, ~ 18km 2-catergory zero-layer thermodynamics [Hibler, 1980] Viscous plastic dynamics [Hibler, 1979] Initial conditions: Polar Science Center Snow simulation: [Zhang et al., 1998]

AOMIP workshop #12 Jan 14-16, 2009 WHOI ECCO2 Arctic Solution Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m

AOMIP workshop #12 Jan 14-16, 2009 WHOI ECCO2 Arctic Solution Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m

AOMIP workshop #12 Jan 14-16, 2009 WHOI Sensitivity Experiments Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m Table.1 1: Nansen Basin 2: Amundsen Basin 3: Makarov Basin 4: Canadian Basin 5: Chukchi Cap Data: SCICEX BGEP

AOMIP workshop #12 Jan 14-16, 2009 WHOI Results: mixed layer depth Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m A0’ 0m50m A0 Table.1 A0’ 2006 A A0 1992

AOMIP workshop #12 Jan 14-16, 2009 WHOI Results: Amundsen Basin Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m Table.1 SCICEX, 2000

AOMIP workshop #12 Jan 14-16, 2009 WHOI Results: Canadian Basin Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m Table.1 BGEP 2003

AOMIP workshop #12 Jan 14-16, 2009 WHOI Results: Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m Blue: off Red: on

AOMIP workshop #12 Jan 14-16, 2009 WHOI Concern: Heat content Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m [Holloway, 2007]

AOMIP workshop #12 Jan 14-16, 2009 WHOI Summary Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m brine rejection:  realistic MLD (compared to climatology)  best fit to CTD observations in all basins  reproduces halocline  improve vertical stratification in Eurasian Basin background diffusivity = m 2 /s  too much artificial vertical mixing reduce  eliminates vertical mixing  optimized = m 2 /s

AOMIP workshop #12 Jan 14-16, 2009 WHOI Coordinated experiment

AOMIP workshop #12 Jan 14-16, 2009 WHOI Model: Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m  KPP, back-ground diffusivity = m 2 /s  Forcings: ERA40/ECMWF  BCs: WOA05 or global solutions  IC: WOA05  Brine Rejection:  A package in the MITgcm  Mixed layer depth (MLD): determined based on d  /dr  When sea-ice forms  salt rejected  buoyancy terms in KPP  distribute buoyancy down to MLD A0’ 2006

AOMIP workshop #12 Jan 14-16, 2009 WHOI Data: Fig.4: Numerical result of salt rejected into a density-stratified fluid. The salt plume of horizontal extent b reaches the neutral buoyancy depth z before spreading out horizontally. Figure is taken from [Smith, 1998]. b~200m z~40m  SCICEX  BGEP  ASOF