Arctic surface waters release methane but also absorb 2,000 times the CO2 for a net cooling effect

Posted by mmaheigan 
· Thursday, September 28th, 2017 

A recent study by Pohlman et al. published in PNAS showed that ocean waters near the surface of the Arctic Ocean absorbed 2,000 times more carbon dioxide (CO2) from the atmosphere than the amount of methane released into the atmosphere from the same waters. The study was conducted near Norway’s Svalbard Islands, which overly numerous seafloor methane seeps.

Methane is a more potent greenhouse gas than CO2, but the removal of CO2 from the atmosphere where the study was conducted more than offset the potential warming effect of the observed methane emissions. During the study, scientists continuously measured the concentrations of methane and CO2 in near-surface waters and in the air just above the ocean surface. The measurements were taken over methane seeps fields at water depths ranging from 260 to 8530 feet (80 to 2600 meters).

Figure 1. Ocean waters overlying shallow-water methane seeps (white dots) offshore from the Svalbard Islands absorb substantially more atmospheric carbon dioxide than the methane that they emit to the atmosphere. Colors indicate the strength of the negative greenhouse warming potential associated with carbon dioxide influx to these surface waters relative to the positive greenhouse warming potential associated with the methane emissions. Gray shiptracks have background values for the relative greenhouse warming potential.

Analysis of the data confirmed that methane was entering the atmosphere above the shallowest (water depth of 260-295 feet or 80-90 meters) Svalbard margin seeps. The data also showed that significant amounts of CO2 were being absorbed by the waters near the ocean surface, and that the cooling effect resulting from CO2 uptake is up to 230 times greater than the warming effect expected from the methane emitted.

Most previous studies have focused only on the sea-air flux of methane overlying seafloor seep sites and have not accounted for the drawdown of CO2 that could offset some of the atmospheric warming potential of the methane. Phytoplankton appeared to be more active in the near-surface waters overlying the seafloor methane seeps, which would explain why so much carbon dioxide was being absorbed. Physical and biogeochemical measurements of near-surface waters overlying the seafloor methane seeps showed strong evidence of upwelling of cold, nutrient-rich waters from depth, stimulating phytoplankton activity and increasing CO2 drawdown. This study was the first to document this CO2 drawdown mechanism in a methane source region.

“If what we observed near Svalbard occurs more broadly at similar locations around the world, it could mean that methane seeps have a net cooling effect on climate, not a warming effect as we previously thought,” said USGS biogeochemist John Pohlman, the paper’s lead author. “We are looking forward to testing the hypothesis that shallow-water methane seeps are net greenhouse gas sinks in other locations.”

 

Authors:
John W. Pohlman (USGS Woods Hole Coastal & Marine Science Center)
Jens Greinert (GEOMAR, Univ. of Tromsø, Royal Netherlands Institute for Sea Research)
Carolyn Ruppel (USGS Woods Hole Coastal & Marine Science Center)
Anna Silyakova (Univ. of Tromsø)
Lisa Vielstädte (GEOMAR)
Michael Casso (USGS Woods Hole Coastal & Marine Science Center)
Jürgen Mienert (Univ. of Tromsø)
Stefan Bünz (Univ. of Tromsø)

Filter by Keyword

abundance acidification additionality advection africa air-sea air-sea interactions algae alkalinity allometry ammonium AMO AMOC anoxic Antarctic Antarctica anthro impacts anthropogenic carbon anthropogenic impacts aquaculture aquatic continuum aragonite saturation arctic Argo argon arsenic artificial seawater Atlantic atmospheric CO2 atmospheric nitrogen deposition authigenic carbonates autonomous platforms bacteria bathypelagic BATS BCG Argo benthic bgc argo bio-go-ship bio-optical bioavailability biogeochemical cycles biogeochemical models biogeochemistry Biological Essential Ocean Variables biological pump biophysics bloom blue carbon bottom water boundary layer buffer capacity C14 CaCO3 calcification calcite carbon carbon-climate feedback carbon-sulfur coupling carbonate carbonate system carbon budget carbon cycle carbon dioxide carbon export carbon sequestration carbon storage Caribbean CCA CCS changing marine chemistry changing marine ecosystems changing marine environments changing ocean chemistry chemical oceanographic data chemical speciation chemoautotroph chesapeake bay chl a chlorophyll circulation climate change climate variability CO2 coastal and estuarine coastal darkening coastal ocean cobalt Coccolithophores commercial community composition conservation cooling effect copepod copepods coral reefs CTD currents cyclone daily cycles data data access data assimilation database data management data product Data standards DCM dead zone decadal trends decomposers decomposition deep convection deep ocean deep sea coral deoxygenation depth diatoms DIC diel migration diffusion dimethylsulfide dinoflagellate dinoflagellates discrete measurements distribution DOC DOM domoic acid DOP dust DVM ecology economics ecosystem management ecosystems eddy Education EEZ Ekman transport emissions ENSO enzyme equatorial current equatorial regions ESM estuarine and coastal carbon fluxes estuary euphotic zone eutrophication evolution export export fluxes export production EXPORTS extreme events faecal pellets fecal pellets filter feeders filtration rates fire fish Fish carbon fisheries fishing floats fluid dynamics fluorescence food webs forage fish forams freshening freshwater frontal zone functional role future oceans geochemistry geoengineering geologic time GEOTRACES glaciers gliders global carbon budget global ocean global warming go-ship grazing greenhouse gas Greenland ground truthing groundwater Gulf of Maine Gulf of Mexico Gulf Stream gyre harmful algal bloom high latitude human food human impact human well-being hurricane hydrogen hydrothermal hypoxia ice age ice cores ice cover industrial onset inland waters in situ inverse circulation ions iron iron fertilization isotopes jellies katabatic winds kelvin waves krill kuroshio lab vs field land-ocean continuum larvaceans lateral transport LGM lidar ligands light light attenuation lipids machine learning mangroves marine carbon cycle marine heatwave marine particles marine snowfall marshes mCDR Mediterranean meltwater mesopelagic mesoscale mesoscale processes metagenome metals methane methods microbes microlayer microorganisms microplankton microscale microzooplankton midwater mitigation mixed layer mixed layers mixing mixotrophs mixotrophy model modeling model validation mode water molecular diffusion MPT MRV multi-decade n2o NAAMES NASA NCP nearshore net community production net primary productivity new ocean state new technology Niskin bottle nitrate nitrogen nitrogen cycle nitrogen fixation nitrous oxide north atlantic north pacific nuclear war nutricline nutrient budget nutrient cycles nutrient cycling nutrient limitation nutrients OA ocean-atmosphere ocean acidification ocean acidification data ocean alkalinity enhancement ocean carbon storage and uptake ocean carbon uptake and storage ocean color ocean modeling ocean observatories ocean warming ODZ oligotrophic omics OMZ open ocean optics organic particles oscillation outwelling overturning circulation oxygen pacific paleoceanography PAR parameter optimization parasite particle flux particles partnerships pCO2 PDO peat pelagic PETM pH phenology phosphate phosphorus photosynthesis physical processes physiology phytoplankton PIC piezophilic piezotolerant plankton POC polar polar regions policy pollutants precipitation predation predator-prey prediction pressure primary productivity Prochlorococcus prokaryotes proteins pteropods pycnocline radioisotopes remineralization remote sensing repeat hydrography residence time resource management respiration resuspension rivers rocky shore Rossby waves Ross Sea ROV salinity salt marsh satellite scale seafloor seagrass sea ice sea level rise seasonal seasonality seasonal patterns seasonal trends sea spray seawater collection seaweed secchi sediments sensors sequestration shelf ocean shelf system shells ship-based observations shorelines silica silicate silicon cycle sinking sinking particles size SOCCOM soil carbon southern ocean south pacific spatial covariations speciation SST state estimation stoichiometry subduction submesoscale subpolar subtropical sulfate surf surface surface ocean Synechococcus technology teleconnections temperate temperature temporal covariations thermocline thermodynamics thermohaline thorium tidal time-series time of emergence titration top predators total alkalinity trace elements trace metals trait-based transfer efficiency transient features Tris trophic transfer tropical turbulence twilight zone upper ocean upper water column upwelling US CLIVAR validation velocity gradient ventilation vertical flux vertical migration vertical transport volcano warming water clarity water mass water quality waves weathering western boundary currents wetlands winter mixing zooplankton

Copyright © 2024 - OCB Project Office, Woods Hole Oceanographic Institution, 266 Woods Hole Rd, MS #25, Woods Hole, MA 02543 USA Phone: 508-289-2838  •  Fax: 508-457-2193  •  Email: ocb_news@us-ocb.org

link to nsflink to noaalink to WHOI

Funding for the Ocean Carbon & Biogeochemistry Project Office is provided by the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA). The OCB Project Office is housed at the Woods Hole Oceanographic Institution.