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Review ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Mar. Sci. | doi: 10.3389/fmars.2019.00432

Measuring Global Ocean Heat Content to estimate the Earth Energy Imbalance

  • 1UMR5566 Laboratoire d'études en géophysique et océanographie spatiales (LEGOS), France
  • 2National Centers for Environmental Information, National Oceanic and Atmospheric Administration, United States
  • 3Applied Physics Laboratory, University of Washington, United States
  • 4NASA Jet Propulsion Laboratory (JPL), United States
  • 5Department of Atmospheric Science, Walter Scott Jr College of Engineering, Colorado State University, United States
  • 6Center for Earth System Research and Sustainability, Department of Earth Sciences, University of Hamburg, Germany
  • 7Langley Research Center, United States
  • 8University of Wisconsin-Madison, United States
  • 9Collecte Localisation Satellites (CLS), France
  • 10University of St. Thomas, United States
  • 11Climate Change Research Centre, University of New South Wales, Australia
  • 12Climate Science Centre, Commonwealth Scientific and Industrial Research Organization, Australia
  • 13International Center for Climate and Environmental Sciences, Institute of Atmospheric Physics (CAS), China
  • 14Institute for Marine and Antarctic Studies, College of Sciences and Engineering, University of Tasmania, Australia
  • 15Antarctic Climate and Ecosystems Cooperative Research Centre, Australia
  • 16Australian Research Council Centre of Excellence for Climate System Science, Australia
  • 17Scripps Institution of Oceanography, University of California, San Diego, United States
  • 18Integrated Climate Data Center, University of Hamburg, Germany
  • 19Meteorological Research Institute (MRI), Japan
  • 20Pacific Marine Environmental Laboratory (NOAA), United States
  • 21Met Office Hadley Centre (MOHC), United Kingdom
  • 22Climate Program Office (NOAA), United States
  • 23Joint Institute for Marine and Atmospheric Research, School of Ocean and Earth Science and Technology, University of Hawaii at Mānoa, United States
  • 24Mercator Ocean (France), France
  • 25École Normale Supérieure, France
  • 26College of Meteorology and Oceanography, National University of Defense Technology, China
  • 27Woods Hole Oceanographic Institution, United States

The energy radiated by the Earth towards 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 gases 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 order of magnitude smaller than the radiation fluxes in and out of the Earth. 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 estimate 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.

Keywords: ocean heat content (OHC), Sea level, Ocean mass, Ocean surface fluxes, ARGO, altimetry, GRACE (Gravity recovery and climate experiment), CERES, internal tide tomography, Earth Energy Imbalance

Received: 08 Nov 2018; Accepted: 05 Jul 2019.

Edited by:

Maria Snoussi, Mohammed V University, Morocco

Reviewed by:

Ru Chen, University of California, Los Angeles, United States
Patrick Heimbach, University of Texas at Austin, United States  

Copyright: © 2019 Meyssignac, Boyer, Zhao, Hakuba, Landerer, Stammer, Köhl, Kato, L'Ecuyer, Ablain, Abraham, Blazquez, Cazenave, Church, Cowley, Cheng, Domingues, Giglio, Gouretski, Ishii, Johnson, Killick, Legler, Llovel, Lyman, Palmer, Piotrowicz, Purkey, Roemmich, Roca, Savita, von Schuckmann, Speich, Stephens, Wang, Wijffels and Zilberman. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Benoit Meyssignac, UMR5566 Laboratoire d'études en géophysique et océanographie spatiales (LEGOS), Toulouse, France, benoit.meyssignac@legos.obs-mip.fr