Vulnerability of the ocean biological pump Corinne Le Quéré University of East Anglia and British Antarctic Survey See notes in individual slides

oceanic carbon cycle numbers in PgC/yr atmosphere 90 CO2 chemical reactions biological activity 11 45 CO2 + H2O + CO2-3 2HCO-3 34 physical transport 11 33 Illustration with numbers ocean

biological activity atmosphere surface 100 m mixed layer depth

biological activity atmosphere 100 m real surface

Ecosystem composition Respiration 34 PgC/y pico-heterotrophs bacteria phyto-plankton pico-autotrophs N2-fixers calcifiers DMS-producers mixed silicifiers Primary Production 45 PgC/y Export 11 PgC/y These are the roles that each PFT plays for the cycle of carbon and nutrients. zoo-plankton proto meso macro

what controls export?

what they do pico-autotrophs Primary Production N2-fixers 45 PgC/y phyto-plankton calcifiers DMS-producers mixed silicifiers These are the roles that each PFT plays for the cycle of carbon and nutrients.

what they do these bloom pico-autotrophs N2-fixers phyto-plankton calcifiers DMS-producers mixed silicifiers These are the roles that each PFT plays for the cycle of carbon and nutrients.

what they do these form shells pico-autotrophs N2-fixers phyto-plankton calcifiers DMS-producers mixed silicifiers These are the roles that each PFT plays for the cycle of carbon and nutrients.

what they do these respond to pH pico-autotrophs N2-fixers phyto-plankton calcifiers DMS-producers mixed silicifiers These are the roles that each PFT plays for the cycle of carbon and nutrients.

what they do these float pico-autotrophs N2-fixers phyto-plankton calcifiers DMS-producers mixed silicifiers These are the roles that each PFT plays for the cycle of carbon and nutrients.

what they need Si pico-autotrophs N2-fixers phyto-plankton calcifiers Fe P N Si N2-fixers phyto-plankton calcifiers DMS-producers mixed silicifiers These are the roles that each PFT plays for the cycle of carbon and nutrients.

what they do Respiration 34 PgC/y pico-heterotrophs bacteria These are the roles that each PFT plays for the cycle of carbon and nutrients. zoo-plankton proto meso macro

what they do these control blooms bacteria pico-heterotrophs proto These are the roles that each PFT plays for the cycle of carbon and nutrients. proto zoo-plankton meso macro

these produce big feacal pellets what they do bacteria pico-heterotrophs these produce big feacal pellets These are the roles that each PFT plays for the cycle of carbon and nutrients. proto zoo-plankton meso macro

what they need F O D D bacteria pico-heterotrophs proto zoo-plankton These are the roles that each PFT plays for the cycle of carbon and nutrients. proto F O D zoo-plankton meso macro F O D

time scale phytoplankton turnover time: 1 week bacterial respiration: 1 day zooplankton turnover time: 1-many weeks sinking rate: 50 m/day

time scale a few days a few +1 days

Q10=3.0 Q10=1.9 Q10=2.2 HOT SPOTS: TEMPERATURE RESPONSE Respiration 34 PgC/y bacteria pico-heterotrophs pico-autotrophs Primary Production 45 PgC/y N2-fixers Export 11 PgC/y phyto-plankton calcifiers DMS-producers mixed silicifiers These are the roles that each PFT plays for the cycle of carbon and nutrients. proto zoo-plankton meso macro

Respiration 34 PgC/y Primary Production 45 PgC/y Export 11 PgC/y HOT SPOTS: pH RESPONSE Respiration 34 PgC/y bacteria pico-heterotrophs pico-autotrophs Primary Production 45 PgC/y N2-fixers Export 11 PgC/y phyto-plankton reduced ballast DMS-producers mixed silicifiers These are the roles that each PFT plays for the cycle of carbon and nutrients. proto zoo-plankton meso macro

? HOT SPOTS: RESPONSE TO STRATIFICATION Respiration 34 PgC/y bacteria pico-heterotrophs pico-autotrophs Primary Production 45 PgC/y N2-fixers Export 11 PgC/y phyto-plankton calcifiers DMS-producers mixed silicifiers These are the roles that each PFT plays for the cycle of carbon and nutrients. ? proto zoo-plankton meso macro

oceanic carbon cycle numbers in PgC/yr atmosphere 90 CO2 chemical reactions biological activity 11 45 CO2 + H2O + CO2-3 2HCO-3 34 physical transport 11 33 Illustration with numbers ocean

CO2 sink (PgC/y) Export (PgC/y) 4 10 14 in one decade 4 10 Export (PgC/y) Results from sensitivity study. We have artificially enhanced biological export in the model. 80% of the change in export is directly taken from the atmosphere. This suggests that if there are any changes in the 11 PgC/y exported from biological processes, the oceanic CO2 sink will change by nearly the same amount. 14 in one decade

the ecosystem composition and the physical transport what controls export? the ecosystem composition and the physical transport

what controls export in models? the ecosystem composition = the physical transport

models air-sea fluxes export PO4 Phyto DOC Zoo POC Most widely used models are much too simple to reproduce the more complex behavior of the ecosystems in the ocean. export

C L I M A T E R E S P O NS E O F OCE N U PT KE a r mi e nto et l. (1 9 8 ) ate r a n d H i s t (1 J o os e t l. ( 19 me p - 20 6 5 18 210 17 W rm g f ct -11 % -1 2 3 Anthropogenic Effect 2% B iolo gi cal Pump + 4 TA Models that estimate the impact of climate change on CO2 fluxes have similar net results (i.e. a decrease of about 5% of the CO2 sink), BUT they are quite different in their estimate of the effect of circulation on the natural carbon. The reason why their net effect is the same is because their circulation and biological effects compensate one another. I think this is because they all use very rigid biology models that directly respond to changes in ocean physics in similar way. I think the biological part should be less tightly linked to the ocean physics. When this is the case, the response of the ocean CO2 sink to climate change should become less similar in the models. (slide adapted from J. Sarmiento)

observations?

Global changes in Atmospheric Potential Oxygen models only 3 models show similar variability

Global changes in Atmospheric Potential Oxygen Slide not available because the data is not published. APO data shows at least 2x more variability than the models. 3 models show similar variability

Interannual chla variability (mgChl/m3) Observations (SeaWiFS) NPZD PO4 DOC Zoo POC export PISCES-T DGOM Calcifiers PO4 Fe

Interannual chla variability (percent) Observations (SeaWiFS) NPZD PISCES-T DGOM None of the models can reproduce the interannual variability in surface chla. We think it may be because of the absence of bacteria and their associated temperature-dependent processes.

model projection of climate change in 2060 temperature mixed layer depth ice cover Results from forced climate change experiments. The impact of climate change is very different depending on which model is used. The ocean CO2 sink in the North Atlantic is collapsing when we use the DGOM compared to the PISCES-T. We have additional temperature dependence of remineralisation in the DGOM which seem to be responsible for the difference in the North Atlantic. This version of the DGOM does not yet include any ballasting.

Impact of climate change on the CO2 sink in 2060 (mol/m2/y) Calcifiers PO4 Fe Results from forced climate change experiments. The impact of climate change is very different depending on which model is used. The ocean CO2 sink in the North Atlantic is collapsing when we use the DGOM compared to the PISCES-T. We have additional temperature dependence of remineralisation in the DGOM which seem to be responsible for the difference in the North Atlantic. This version of the DGOM does not yet include any ballasting. (Preliminary result from E. T. Buitenhuis)

what comes now?

truth time evolution of model results (what is the vulnerability of the marine biological pump?) illusion time

truth time evolution of model results (what is the vulnerability of the marine biological pump?) illusion chaos time

truth time evolution of model results ocean biogeochemistry models (what is the vulnerability of the marine biological pump?) relief illusion chaos time

thanks to Erik T. Buitenhuis and Olivier Aumont for providing model codes and results