Ocean biogeochemistry in the Canadian Earth System Model 5 (CanESM5) Neil Swart ([email protected]), Jim Christian, Andrew Shao, et al. Canadian Centre for Climate Modelling and Analysis (CCCma), Environment and Climate Change Canada, Victoria, BC Canada. Introduction to CanESM5 CanESM5 is CCCma’s latest fully coupled Earth System Model. It updates CanESM2, with new ocean and sea-ice models (NEMO-LIM2), a new coupler, and updates in the atmosphere and land models. CanESM5 will contribute to the Coupled Model Intercomparison Project Phase 6 (CMIP6). CanESM5 nominal ocean resolution is 1 ◦ on the ORCA1 tripo- lar grid, with refinement at the equator. Atmospheric resolution is T63 ( 2.5 ◦ ). Ocean biogeochemistry models Canadian Model of Ocean Carbon (CMOC) • OMIP6 carbon chemistry • NPZD biology with fixed stoichoimetry • Parameterized iron lim- ition, calcium carbonate sinking and N 2 fixation. C N Chl N P Z D DIC TA Chl CO 2 uptake N 2 CaCO 3 Fe mask O 2 • CanESM5 with CMOC will contribute all CMIP6 experiments submitted by CCCma. Canadian Ocean Ecosystem (CanOE) C/O 2 N Fe Chl NO 3 NH 4 dFe P S P L Z S Z L D S D L CaCO 3 O 2 DIC TA • OMIP6 carbon chemistry • 2N2P2Z biology with vari- able phytoplankton stoichoimetry • Explicit iron and calcium carbonate cycles, and denitrification. • CanESM5-CanOE will contribute DECK-hist-SSP and OMIP experiments to CMIP6. Validation and model comparison Ocean only and coupled runs skilfully reproduce the 3D clima- tological distributions of DIC and NO 3 , and the surface CO 2 flux. CMOC and CanOE points are from ocean-only OMIP runs. CanESM2 and CanESM5 are coupled model runs, both with CMOC. • Skill improved in CanESM5 relative to CanESM2 due to bet- ter physical circulation. • CMOC and CanOE have similar global-scale skill. Regional biases differ in CMOC and CanOE under the same circulation. CMOC shows tropical nutrient trapping, while CanOE overestimates bottom water NO 3 , and underestimates NO 3 in NADW. Both models have DIC deficient bottom wa- ters. CMOC CanOE CMOC has excessive NO 3 accumulation in the eastern tropical Pacific, likely due to over-simplified denitrification. CanOE overestimates NO 3 in the Southern Ocean and Indo-Pacific (Circumpolar Deep Water, Antarctic Bottom Water), and underestimates NO 3 in North Atlantic Deep Water. Carbon spinup Ouput from CanESM2 is used to drive NEMO in an OMIP- style ocean only run. 10,000 years of spin-up was achieved, and the resulting restarts used to initialize the CanESM5 spinup run. CanESM5 simulations (CMOC) Zonal mean CO 2 fluxes CanESM2 had an unre- alistic Southern Ocean flux dipole, which is corrected in CanESM5. Historical CO 2 uptake • Ocean carbon uptake is within observation uncer- tainty in CanESM5. • Cumulative carbon uptake is higher in CanESM5 than in CanESM2. Ecosystem response to forcing • Primary production declines over the historical / SSP5-85 experi- ment. • In the 4xCO2 experi- ment declines begin re- covery after about 50 years.

Ocean biogeochemistry in the Canadian Earth System Model 5 … · 2019-04-18 · Ocean biogeochemistry in the Canadian Earth System Model 5 (CanESM5) Neil Swart ([email protected]),

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Page 1: Ocean biogeochemistry in the Canadian Earth System Model 5 … · 2019-04-18 · Ocean biogeochemistry in the Canadian Earth System Model 5 (CanESM5) Neil Swart (neil.swart@canada.ca),

Ocean biogeochemistry in the Canadian Earth System Model 5 (CanESM5)Neil Swart ([email protected]), Jim Christian, Andrew Shao, et al.

Canadian Centre for Climate Modelling and Analysis (CCCma), Environment and Climate Change Canada, Victoria, BC Canada.

Introduction to CanESM5CanESM5 is CCCma’s latest fully coupled Earth System Model.It updates CanESM2, with new ocean and sea-ice models(NEMO-LIM2), a new coupler, and updates in the atmosphereand land models. CanESM5 will contribute to the CoupledModel Intercomparison Project Phase 6 (CMIP6).

CanESM5 nominal ocean resolution is 1◦ on the ORCA1 tripo-lar grid, with refinement at the equator. Atmospheric resolu-tion is T63 ( 2.5◦).

Ocean biogeochemistry modelsCanadian Model of Ocean Carbon (CMOC)

• OMIP6 carbon chemistry

• NPZD biology with fixedstoichoimetry

• Parameterized iron lim-ition, calcium carbonatesinking and N2 fixation.

Chl

DIC TA

ChlCO

2 uptake

CaCO3

Fe mask

• CanESM5 with CMOC will contribute all CMIP6 experi-ments submitted by CCCma.

Canadian Ocean Ecosystem (CanOE)

C/O2

Chl

NO3

NH4

dFe

DS DL

CaCO3O2

DIC TA

• OMIP6 carbon chemistry

• 2N2P2Z biology with vari-able phytoplankton stoi-choimetry

• Explicit iron and calciumcarbonate cycles, and den-itrification.

• CanESM5-CanOE will contribute DECK-hist-SSP and OMIPexperiments to CMIP6.

Validation and model comparisonOcean only and coupled runs skilfully reproduce the 3D clima-tological distributions of DIC and NO3, and the surface CO2

flux.

CMOC and CanOE points are from ocean-only OMIP runs. CanESM2 and CanESM5 are coupled model runs, both withCMOC.

• Skill improved in CanESM5 relative to CanESM2 due to bet-ter physical circulation.

• CMOC and CanOE have similar global-scale skill.

Regional biases differ in CMOC and CanOE under the samecirculation. CMOC shows tropical nutrient trapping, whileCanOE overestimates bottom water NO3, and underestimatesNO3 in NADW. Both models have DIC deficient bottom wa-ters.

CMOC CanOE

CMOC has excessive NO3 accumulation in the eastern tropi-cal Pacific, likely due to over-simplified denitrification. CanOEoverestimates NO3 in the Southern Ocean and Indo-Pacific(Circumpolar Deep Water, Antarctic Bottom Water), and un-derestimates NO3 in North Atlantic Deep Water.

Carbon spinup

Ouput from CanESM2 is used to drive NEMO in an OMIP-style ocean only run. 10,000 years of spin-up was achieved, andthe resulting restarts used to initialize the CanESM5 spinuprun.

CanESM5 simulations (CMOC)Zonal mean CO2 fluxes

CanESM2 had an unre-alistic Southern Oceanflux dipole, which iscorrected in CanESM5.

Historical CO2 uptake

• Ocean carbon uptake iswithin observation uncer-tainty in CanESM5.

• Cumulative carbon uptakeis higher in CanESM5 thanin CanESM2.

Ecosystem response to forcing

• Primary production de-clines over the histor-ical / SSP5-85 experi-ment.

• In the 4xCO2 experi-ment declines begin re-covery after about 50years.