Positive future climate feedback due to changes

in oceanic DMS emissions

OCFUCC INT SCIENT. CONF., PARIS, FRANCE, 7-10 JULY 2015

Jerry Tjiputra1,5, Katharina Six2, Øyvind Seland3, and Christoph Heinze1,4,5

1Uni Research Climate, Bergen, Norway 2Max-Planck-Institute of Meteorology, Hamburg, Germany 3Norwegian meteorological Institute, Oslo, Norway 4University of Bergen, Bergen, Norway 5Bjerknes Centre for Climate Research, Bergen, Norway

DMS

2

Motivations

Modified from Friedlingstein et al. (2006)

COUPLED

UNCOUPLED

Atmospheric CO2 concentration

IPCC-AR4 WG1-Ch.7, Fig 10.20 (2007)

[2.6

– 4

.1°C

] [2

.4 –

5.6

°C]

Additional warming of

0.1 to 1.5 °C

With biogeochemistry

Without biogeochemistry

• Biogeochemical process introduce feedback to future climate change.

3

Motivations

• DMS-climate feedback is currently not included in CMIP5 (IPCC-AR5)

models

• Cloud component in the climate system contributes with the largest source

of uncertainties in future projection (IPCC, 2013).

• Marine dimethylsulphide (DMS) emissions encompass the largest natural

source of atmospheric gaseous sulphur.

• Once released, DMS particles act as CCN, altering cloud composition in

the atmosphere and radiative balance.

• Ocean acidification has been identified to alter DMS production, a potential

additional source of biologically induced feedback on climate.

4

Methods: Norwegian Earth System Model (NorESM1-ME)

CLM-CN

CAM (Atmosphere, ~2°)

CICE

HAMOCC MICOM (Ocean)

~1°, 53L

Atmospheric chemistry

River routing

Sulfur chemistry and

aerosol microphysics

NorESM1-ME model diagram (Bentsen et al., 2013; Tjiputra et al., 2013)

- Fully interactive with prescribed CO2 emissions

- Historical + RCP8.5 scenario (1850-2100)

Marine DMS emissions

5

PO4, NO3, Fe

RC:P N

Phyt oplankt onDiat omsCalcifiers

NPP

Det rit usZooplankton DOC

POC

Chlorophyll

grazing

phot oadapt ion

fecal pellet sexcret ion

bact erial removal

export

& mort alit y

Ocean surface (euphotic layer)

Atmosphere

DMS

Emissions to atmosphere

Six and Maier-Reimer, 2006

Prescribed from

observation

Marine DMS emissions

6

PO4, NO3, Fe

RC:P N

Phyt oplankt onDiat omsCalcifiers

NPP

Det rit usZooplankton DOC

POC

Chlorophyll

grazing

phot oadapt ion

fecal pellet sexcret ion

bact erial removal

export

& mort alit y

Ocean surface (euphotic layer)

Atmosphere

DMS Bacterial

activity

Photolysis

loss

Emissions to atmosphere

Six and Maier-Reimer, 2006

Climate feedback

Ocean acidification

feedback

Processes influence the DMS emissions and feedback

7

• Ocean circulation/upwelling: nutrient availability

• Sea-ice variations: irradiation

• Warming: phytoplankton growth period

• Ocean acidification: DMS production rate

Bopp et al. (2013)

Six et al. (2013)

Validation of annual DMS concentrations and emissions

8

Concentr

ation

E

mis

sio

ns

Observation (Lana et al., 2010) Model

Global annual emissions:

- Prescribed: 18. Tg S

- Interactive: 25. Tg S

- Obs: 17-34 Tg S

Experiment configurations

9

Historical + future scenario RCP8.5 simulations:

• Reference -> no interactive DMS (prescribes DMS concentration)

• Clim -> consider only climate change impact on DMS production

• Clim+pH -> climate change impact and acidification

Clim_pH

NPP pH REF

Clim

Temperature, wind-speed,

sea-ice, circulations, etc.

Projected global DMS emissions (1850-2100)

10

REF

Clim

Clim+pH

-8%

-37%

Projected regional change in DMS emissions

11

Regional changes relative to the preindustrial fluxes (1850s)

Reduce Increase

30-40%

decrease

Projected regional change in DMS emissions

12

+200%

+90%

-40%

-30%

-12%

+4%

Climate change induces heterogeneous regional effect on net primary production

Ocean acidification leads to reduction in DMS emissions (largest at high latitudes)

Projected global mean surface air temperature (1850-2200)

13

±1σ

~+0.4

~+0.5

Projected regional change in mean surface air temperature

14

Projected ∆T (by end of 21st century) is

similar between all experiments (REF,

Clim, and Clim+pH)

When acidification effect is considered,

additional warming as much as 4K are

simulated in the Arctic and Antarctic

Additional temperature change due to DMS-climate feedback

15

pH-effect on DMS production induces additional warming in majority of Earth’s surface,

particularly in the high latitude, potentially due to polar amplification

Impact beyond surface temperature

16

Summary

17

• Oceanic DMS emission is projected to decrease in low- and mid-latitudes, attributed to

climate change (reduction in net primary production).

• In high latitude, warming (higher phytoplankton growth rate) and retreat of sea-ice lead

to increase in DMS outgassing.

• Future ocean acidification broadly decreases the DMS emissions.

• Globally, DMS is projected to introduce additional positive climate feedback.

• The mean global surface temperature at the end of 21st century is projected to be

warmer by approximately 0.4K compare to the simulation without DMS.

• Regionally, as much as 4K additional warming is projected, e.g., in the Arctic.

Funding acknowledged: NFR-EVA (no229771)