Model framework for consistent estimation of climate sensitivity and ocean heat content

Model setup:

• Slab ocean control run (70 years) -> calculated Q-flux
  • Slab ocean (docn)+CAM+CICE+river runoff?
  • run for 70 years
• Slab ocean run -> save coupled fluxes
  • the last 20 years is used
• Ocean-ice model simulation forced with coupler fluxes
  • one experiment with salinity restoration
    • run for 40 years (2 cycles)
  • without salinity restoration
    • run for 120 years (6 cycles)

Slab ocean setup descriptions

(updated, 23 Nov 2022)

The method: calculating the ocean heat transport (Q-fluxes) by relaxing slab ocean SST towards observed SST climatology.

Formulation:

• : estimate of the observed annual mean mixed layer ocean depth (not changed)
• has a typical time scale of ~15 days

Global Averages

3D temp	3D saln	SST	SSS

Overturning circulation, volume transport

AMOC 26.5N	Bering strait	Florida Current	Drake Passage

Temperature/Salnity anomalies

Temperature@0m	Salnity@0m	MLD

Freshwater budget (Salt flux)

net salt flux received by ocean	with minus w/o salinity relaxation
salt relaxation flux-->

Freshwater budget (eva, prec, runoff, etc)

net freshwater received by ocean with salinity relaxation	with minus w/o salinity relaxation
salt flux (with minus w/o salinity relaxation)-->

SOM control run:

Model output
/projects/NS2345K/noresm/thomas/CMIP6/SOM/QS/out/SOj09_hdxpt/cnt_cpldiags

Diagnostics:
http://ns2345k.web.sigma2.no/diagnostics/noresm/yanchun/SOj09_hdxpt/

Ocean-ice run with coupler flux:

• Coupler forcing:
  • store under (betzy is off now):
    • /projects/NS2345K/users/yanchun/FTI2022/SOj09_hdxpt_cplhist_monthly
  • in total 825G (transfer may still in progress)
• Model output: /projects/NS2345K/noresm/cases:
  • with salinity relaxation
    • Casename: NOICPLHISTOC_f09_tn14_cpldiags
    • http://ns2345k.web.sigma2.no/diagnostics/noresm/yanchun/NOICPLHISTOC_f09_tn14_cpldiags
  • w/o salinity relaxation
    • NOICPLHISTOC_f09_tn14_cplhist
    • http://ns2345k.web.sigma2.no/diagnostics/noresm/yanchun/NOICPLHISTOC_f09_tn14_cplhist

Plan for the next?

• Odd Helge:
  • check with coupler flux and the model output, why there is imbalanced fresh water budget (runoff, eva, precp, etc)?
• Yanchun:
  • extend the simulation with salinity relaxation (up to 120 years)
  • start new simulation with only salinity relaxation north of 45N.

Thanks, this is the last slide!

Slab ocean setup descriptions (old)

Two approaches

1. CAM-SOM ("old" way)

The method: calculating the ocean heat transport (Q-fluxes) from an existing CAM simulation with prescribed SST, sea ice extent, and thickness.
Key point: reproduce the observed climate.
Formulation:

• : estimate of the observed annual mean mixed layer ocean depth
• change in the sea surface temperature
• surface net energy balance obtained from a control CAM simulation ().

update: correct to have globa lbalanced flux
Drawbacks:

• Q-fluxes are dominated by the model climate biases?
• missing information of fluxes between the ice and ocean
  • an additional flux was added, given an estimate of ice-fraction from a thermodynamic-only sea ice model

Slab ocean setup descriptions (old)

Two approaches

2. CCSM-SOM ("new" way)

The method: calculating the ocean heat transport (Q-fluxes) from an existing CAM simulation with prescribed SST, sea ice extent, and thickness.
Key points:

• reproduce the coupled climate of the model (,as opposed to the observed climate)
• use full sea-ice model (CICE)
• fully-conservative information about ice-ocean fluxes
  Formulation:

Advantage: , , and from a fully-coupled simulation instead of being based on an estimated mixed-layer depth from observations