Rain increases the global carbon sink

Posted by mmaheigan 
· Tuesday, January 28th, 2025 

The global ocean dampens the anthropic CO2 increase in the atmosphere by absorbing around 25% of the carbon emitted each year. Of the processes involved in exchanges of energy and mass between ocean and atmosphere that may impact this carbon sink, rainfall has never been systematically and comprehensively quantified. A study recently published in Nature Geosciences suggests that about 6% of the global ocean CO2 sink is mediated by rainfall.

Figure 1. Histograms of 2008-2018 global ocean (60°S-60°N) CO2 sink increase due to rain-induced turbulence only, rain-induced dilution only, the resultant of turbulence and dilution (named the interfacial effect), the wet deposition of CO2 absorbed during the raindrops fall and the total (interfacial plus wet deposition) using 1-h rain rates from IMERG (blue) and ERA5 (red). The rain-induced dilution is diagnosed from a satellite-derived empirical relationship (full) or a 1D physical model (stripes). Figure based on Parc et al. (2024) Table 1.

The exchange of CO2 at the ocean interface is controlled by chemical, physical, and biological properties and processes. Rainfall, one of these processes, can alter the properties of the ocean surface and perturb the carbon exchange in three ways:

(i) Turbulence: Raindrops increase the momentum transfer to the ocean and generate turbulence enhancing the renewal of interfacial water (first column in Fig. 1). This tends to increase both in- and out-gassing. The impact of this effect alone is weak because wind dominates the generation of turbulence in the ocean;

(ii) Dilution + Interfacial: Rain dilutes and cools the near surface waters, which perturbs chemical equilibria and leads the ocean to absorb more CO2 (second column in Fig. 1). The result of dilution and turbulence effects of rain, which is named “Interfacial”, is a clear increase in global CO2 sink (third column in Fig. 1);

(iii) Wet deposition: Finally, raindrops directly inject CO2 molecules into the ocean that they absorbed during their fall through the atmosphere (fourth column in Fig. 1).

Using two rainfall datasets (the satellite-derived product IMERG and the ERA5 reanalysis) and two ways to quantify the rain-induced dilution, the authors show that rain increases the ocean carbon sink by 140 to 190 million tonnes of carbon per year, equivalent to 5% to 7% of the 2.66 billion tonnes of carbon absorbed annually by the oceans. Because rainfall amounts and patterns will change in the future, impacting the ocean carbon sink, these results call for explicitly including rain effects in the annual global carbon budget estimates.

Authors
Laëtitia Parc (Laboratoire de Météorologie Dynamique)
Hugo Bellenger (Laboratoire de Météorologie Dynamique)
Laurent Bopp (Laboratoire de Météorologie Dynamique) @bopplaurent.bsky.social
Xavier Perrot (Laboratoire de Météorologie Dynamique)
David T. Ho (University of Hawaii at Manoa; [C]Worthy) @davidho.bsky.social

 

Parc, L., Bellenger, H., Bopp, L., Perrot, X., and Ho, D. T. Global ocean carbon uptake enhanced by rainfall.Nat. Geosci. 17, 851–857 (2024). https://doi.org/10.1038/s41561-024-01517-y

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 appendicularia 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 fluxes 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 CO2 coastal and estuarine coastal darkening coastal ocean cobalt Coccolithophores commercial community composition competition 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 denitrification 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 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 gelatinous zooplankton geochemistry geoengineering geologic time GEOTRACES glaciers gliders global carbon budget global ocean global warming go-ship grazing greenhouse gas greenhouse gases 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 iron limitation isotopes jellies katabatic winds kelvin waves krill kuroshio lab vs field land-ocean continuum larvaceans lateral transport LGM lidar ligands light light attenuation lipids low nutrient machine learning mangroves marine carbon cycle marine heatwave marine particles marine snowfall marshes mCDR mechanisms 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 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 North Sea nuclear war nutricline nutrient budget nutrient cycles nutrient cycling nutrient limitation nutrients OA observations 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 productivity 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 siderophore 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 trawling 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 warming water clarity water mass water quality waves weathering western boundary currents wetlands winter mixing zooplankton

Copyright © 2025 - 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.