The energy radiated by the Earth toward space does not compensate the incoming radiation from the Sun leading to a small positive energy imbalance at the top of the atmosphere (0.4-1 Wm(-2)). This imbalance is coined Earth's Energy Imbalance (EEI). It is mostly caused by anthropogenic greenhouse gas emissions and is driving the current warming of the planet. Precise monitoring of EEI is critical to assess the current status of climate change and the future evolution of climate. But the monitoring of EEI is challenging as EEI is two orders of magnitude smaller than the radiation fluxes in and out of the Earth system. Over 93% of the excess energy that is gained by the Earth in response to the positive EEI accumulates into the ocean in the form of heat. This accumulation of heat can be tracked with the ocean observing system such that today, the monitoring of Ocean Heat Content (OHC) and its long-term change provide the most efficient approach to estimate EEI. In this community paper we review the current four state-of-the-art methods to estimate global OHC changes and evaluate their relevance to derive EEI estimates on different time scales. These four methods make use of: (1) direct observations of in situ temperature; (2) satellite-based measurements of the ocean surface net heat fluxes; (3) satellite-based estimates of the thermal expansion of the ocean and (4) ocean reanalyses that assimilate observations from both satellite and in situ instruments. For each method we review the potential and the uncertainty of the method to estimate global OHC changes. We also analyze gaps in the current capability of each method and identify ways of progress for the future to fulfill the requirements of EEI monitoring. Achieving the observation of EEI with sufficient accuracy will depend on merging the remote sensing techniques with in situ measurements of key variables as an integral part of the Ocean Observing System.
1.Univ Toulouse, IRD, UPS, CNRS,CNES,LEGOS, Toulouse, France 2.NOAA, Natl Ctr Environm Informat, Silver Spring, MD USA 3.Univ Washington, Appl Phys Lab, Seattle, WA 98105 USA 4.CALTECH, Jet Prop Lab, Pasadena, CA USA 5.Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA 6.Univ Hamburg, Ctr Erdsyst Forsch & Nachhaltigkeit, Hamburg, Germany 7.NASA, Langley Res Ctr, Hampton, VA 23665 USA 8.Univ Wisconsin, Dept Atmospher & Ocean Sci, Madison, WI USA 9.Collecte Localisat Satellite, Ramonville St Agne, France 10.Univ St Thomas, St Paul, MN USA 11.Univ New South Wales, Climate Change Res Ctr, Sydney, NSW, Australia 12.Commonwealth Sci & Ind Res Org, Climate Sci Ctr, Hobart, Tas, Australia 13.Chinese Acad Sci, Int Ctr Climate & Environm Sci, Inst Atmospher Phys, Beijing, Peoples R China 14.Univ Tasmania, Inst Marine & Antarctic Studies, Hobart, Tas, Australia 15.Antarctic Climate & Ecosyst Cooperat Res Ctr, Hobart, Tas, Australia 16.Australian Res Council, Ctr Excellence Climate Syst Sci, Hobart, Tas, Australia 17.Univ Colorado, Dept Atmospher & Ocean Sci, Boulder, CO 80309 USA 18.Univ Hamburg, Ctr Earth Syst Res & Sustainabil, Integrated Climate Data Ctr, CliSAP, Hamburg, Germany 19.Japan Meteorol Agcy, Meteorol Res Inst, Tsukuba, Ibaraki, Japan 20.NOAA, Pacific Marine Environm Lab, 7600 Sand Point Way Ne, Seattle, WA 98115 USA 21.Hadley Ctr, Met Off, Exeter, Devon, England 22.NOAA, Climate Program Off, Silver Spring, MD USA 23.Univ Hawaii Manoa, Joint Inst Marine & Atmospher Res, Honolulu, HI 96822 USA 24.Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA 25.Mercator Ocean Int, Ramonville St Agne, France 26.Ecole Normale Super, Lab Meteorol Dynam, Paris, France 27.Natl Univ Def Technol, Coll Meteorol & Oceanog, Nanjing, Jiangsu, Peoples R China 28.Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA
Recommended Citation:
Meyssignac, Benoit,Boyer, Tim,Zhao, Zhongxiang,et al. Measuring Global Ocean Heat Content to Estimate the Earth Energy Imbalance[J]. FRONTIERS IN MARINE SCIENCE,2019-01-01,6