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Author Topic: Global Warming Amplified by reduced Sulfur Fluxes, result of Ocean Acidification  (Read 3596 times)

TeaPotty

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Global Warming Amplified by reduced Sulfur Fluxes as a result of Ocean Acidification:
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1981.html

Quote
Abstract

Climate change and decreasing seawater pH (ocean acidification)1 have widely been considered as uncoupled consequences of the anthropogenic CO2 perturbation2, 3. Recently, experiments in seawater enclosures (mesocosms) showed that concentrations of dimethylsulphide (DMS), a biogenic sulphur compound, were markedly lower in a low-pH environment4. Marine DMS emissions are the largest natural source of atmospheric sulphur5 and changes in their strength have the potential to alter the Earth’s radiation budget6. Here we establish observational-based relationships between pH changes and DMS concentrations to estimate changes in future DMS emissions with Earth system model7 climate simulations. Global DMS emissions decrease by about 18(±3)% in 2100 compared with pre-industrial times as a result of the combined effects of ocean acidification and climate change. The reduced DMS emissions induce a significant additional radiative forcing, of which 83% is attributed to the impact of ocean acidification, tantamount to an equilibrium temperature response between 0.23 and 0.48 K. Our results indicate that ocean acidification has the potential to exacerbate anthropogenic warming through a mechanism that is not considered at present in projections of future climate change.

Relationship between DMS concentration and pH based on data from mesocosm experiments:


Changes in annual mean pH and annual mean model fluxes between the years 2090–2099 and 1865–1874:


Changes in annual zonal mean of top-of-the-atmosphere radiative forcing and of DMS emission between the years 2090–2099 and 1865–1874.


Also in Time magazine:
http://science.time.com/2013/08/26/ocean-acidification-will-make-climate-change-worse/
...and Yale 360:
http://e360.yale.edu/digest/ocean_acidification_could__amplify_global_warming_study_says/3932/

Bruce Steele

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Teapotty, I tried to find out how many mesocosm studies this research was based on but until I see the paper I won't know. The phytoplankton communities change in tropical or polar conditions and different members of the phytoplankton community respond differently to acidification. To get a good idea on how different areas of the oceans respond someone would need to run multiple mesocosms . The initial work done shows a 18% methyl sulfide production drop by 2100. Atmospheric Co2 should be over 900 ppm , temps. 4 to 6 C increase on land with an additional .23 to .48 C if this study is correct. Ocean pH will have decreased by ~. 4 and ocean temperature increased by 2 to 3 degrees C. If we actually pull the trigger and get to 900 ppm Co2 by 2100 we will continue to see ocean pH drop between 2100 and 2300. This would require the burning of most of the coal and oil reserves known. It seems like we are still headed to 900 . If we do continue this long enough we can change the average ocean pH by an additional .3 by 2300 with a resultant average surface ocean pH of 7.5
The researchers probably didn't run their mesocosm down to 7.5 pH or the 7.3 potential in arctic waters.   Kinda like the difference between running a crash test dummy into a wall at 120 mph or 200 mph.  The dummy doesn't make it.

Bruce Steele

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Arctic mesocosm study( Archer et al 2013 ) " Concentrations of DMS were reduced by 35% at intermediate and 60% at high pCo2 levels relative to ambient pCo2.". " in contrast , concentrations of DMSP the precursor of DMS were elevated by 30% and 50% at intermediate and high pCO2 respectively. Elevated DMSP production at high pCO2 correlates positively with higher dinoflagellate biomass."
 The mesocosm study showed a shift from diatoms to dinoflagellates at high pCO2 levels ( 675-1085 uatm). Nutrient additions had an effect on the outcome of this mesocosm study and efforts to more closely mirror natural timing of nutrient concentrations may show somewhat different responses.
http://www.biogeosciences.net/10/5619/2013/bg-10-5619-2013.pdf

Here is another paper by PMEL ( pacific Marine environmental lab ) on worldwide DMS concentrations based on shipbased cruises.
http://saga.pmel.noaa.gov/review/dms_climate.html

We need to better understand diatom and dinoflagellate responses to acidifications as well as bacterial and viral responses in tropical and temperate oceans before projections of future DMS production changes due to ocean acidification can be quantified.