ARCTIC SYNTHESISARCTIC SYNTHESIS

Ecosystem Modeling StatusEcosystem Modeling Status

Yvette H. Spitz and LYvette H. Spitz and Léo Berlineéo Berline

OSU-COASOSU-COAS

Chlorophyll a SeaWifs climatology Model 1986

White line : ice edge

Annual primary production

Model 1986 VGPM 1998 (Behrenfeld and Falkowski. 1997)

Observations11-component model

•Coded new ecosystem model Coded new ecosystem model – 2 phytoplankton (pico and diatom) and 2 2 phytoplankton (pico and diatom) and 2

zooplanktonzooplankton– Full microbial loopFull microbial loop– Nitrate, Ammonium and SilicateNitrate, Ammonium and Silicate

• Diagnostic preliminary runs 3DDiagnostic preliminary runs 3D

Nitrate concentration

after one year of run

Problem vertical diffusion• High surface nitrate concentration in the north Chukchi Sea

Time (month)

Dep

th (

m)

− Deep mixing that leads to high nutrient in the surface and therefore artificially high bloom. Changed Eq of state in POP (Jacket and McDougall, 1995, instead of the traditional polynomial fit to the UNESCO eqn of state), which improved slightly the density field

− Light penetration and mixing seems to pose problems for us - Ice model might need tuning

− Open Boundary conditions at the Strait might help to retain some nutrient on the shelf

New Eq of State UNESCO Eq of State

Salinity

New Eq of State

UNESCO Eq of State

Temperature

Nitrate initial condition for winter

• Levitus in GIN• Colony in Can Basin• Value from literature on

shelves

Location 1D model Tests

ChukchiSHEBA

Greenland

• 3 different ice cover

Greenland 1D outputs

NO3

Chl

Blue : model, Red: obs (Cota)

Greenland 1D outputs

NO3

Chl

Blue : model, Red: obs (Cota) T-Dependence of growth

Chukchi 1D outputs

July, end of simulation

Blue : model, Red: obs (SBI)

QuestionsQuestions

• GreenlandGreenland– Is nitrate not depleted in summer?Is nitrate not depleted in summer?– Is it general for GIN?Is it general for GIN?

• ChukchiChukchi– Is benthic remineralization important?Is benthic remineralization important?– Need to go further north to avoid Need to go further north to avoid

contamination by Bering Straitcontamination by Bering Strait• Modeled phytoplanktonModeled phytoplankton

– Main taxa: Diatom, auto. Dinoflagellates ok?Main taxa: Diatom, auto. Dinoflagellates ok?– Importance phaeocystis?Importance phaeocystis?– Chl/C Value valid arctic-wide?Chl/C Value valid arctic-wide?