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Title: Improved estimates of ocean heat content from 1960 to 2015

Abstract

Earth’s energy imbalance (EEI) drives the ongoing global warming and can best be assessed across the historical record (that is, since 1960) from ocean heat content (OHC) changes. An accurate assessment of OHC is a challenge, mainly because of insufficient and irregular data coverage. We provide here updated OHC estimates with the goal of minimizing associated sampling error. We performed a subsample test, in which subsets of data during the datarich Argo era are colocated with locations of earlier ocean observations, to quantify this error. Our results provide a new OHC estimate with an unbiased mean sampling error and with variability on decadal and multidecadal time scales (signal) that can be reliably distinguished fromsampling error (noise) with signal-to-noise ratios higher than 3. The inferred integrated EEI is greater than that reported in previous assessments and is consistent with a reconstruction of the radiative imbalance at the top of atmosphere starting in 1985. We found that changes in OHC are relatively small before about 1980; since then, OHC has increased fairly steadily and, since 1990, has increasingly involved deeper layers of the ocean. In addition,OHC changes in sixmajor oceans are reliable on decadal timescales. All ocean basins examined have experienced significantmore » warming since 1998, with the greatest warming in the southern oceans, the tropical/subtropical Pacific Ocean, and the tropical/subtropical Atlantic Ocean. This new look at OHC and EEI changes over time provides greater confidence than previously possible, and the data sets produced are a valuable resource for further study.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [2];  [3];  [4];  [1]
  1. Chinese Academy of Sciences (CAS), Beijing (China). Inst. of Atmospheric Physics and International Center for Climate and Environment Sciences
  2. National Center for Atmospheric Research, Boulder, CO (United States)
  3. National Oceanic and Atmospheric Administration (NOAA)-National Centers for Environmental Information, Silver Spring, MD (United States)
  4. Univ. of St. Thomas, St. Paul, MN (United States)
Publication Date:
Research Org.:
National Center for Atmospheric Research, Boulder, CO (United States)
Sponsoring Org.:
USDOE; Chinese Academy of Sciences (CAS) (China); National Science Foundation of China; National Science Foundation (NSF); National Aeronautic and Space Administration (NASA); National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States)
OSTI Identifier:
1425658
Grant/Contract Number:
SC0012711; 41506029; 41476016; 2016YFC1401800; 1243125; NNH11ZDA001N
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
Journal Volume: 3; Journal Issue: 3; Journal ID: ISSN 2375-2548
Publisher:
AAAS
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Earth’s energy imbalance; ocean heat content; sampling; mapping; subsample test; global warming; decadal variability; hiatus

Citation Formats

Cheng, Lijing, Trenberth, Kevin E., Fasullo, John, Boyer, Tim, Abraham, John, and Zhu, Jiang. Improved estimates of ocean heat content from 1960 to 2015. United States: N. p., 2017. Web. doi:10.1126/sciadv.1601545.
Cheng, Lijing, Trenberth, Kevin E., Fasullo, John, Boyer, Tim, Abraham, John, & Zhu, Jiang. Improved estimates of ocean heat content from 1960 to 2015. United States. doi:10.1126/sciadv.1601545.
Cheng, Lijing, Trenberth, Kevin E., Fasullo, John, Boyer, Tim, Abraham, John, and Zhu, Jiang. Fri . "Improved estimates of ocean heat content from 1960 to 2015". United States. doi:10.1126/sciadv.1601545. https://www.osti.gov/servlets/purl/1425658.
@article{osti_1425658,
title = {Improved estimates of ocean heat content from 1960 to 2015},
author = {Cheng, Lijing and Trenberth, Kevin E. and Fasullo, John and Boyer, Tim and Abraham, John and Zhu, Jiang},
abstractNote = {Earth’s energy imbalance (EEI) drives the ongoing global warming and can best be assessed across the historical record (that is, since 1960) from ocean heat content (OHC) changes. An accurate assessment of OHC is a challenge, mainly because of insufficient and irregular data coverage. We provide here updated OHC estimates with the goal of minimizing associated sampling error. We performed a subsample test, in which subsets of data during the datarich Argo era are colocated with locations of earlier ocean observations, to quantify this error. Our results provide a new OHC estimate with an unbiased mean sampling error and with variability on decadal and multidecadal time scales (signal) that can be reliably distinguished fromsampling error (noise) with signal-to-noise ratios higher than 3. The inferred integrated EEI is greater than that reported in previous assessments and is consistent with a reconstruction of the radiative imbalance at the top of atmosphere starting in 1985. We found that changes in OHC are relatively small before about 1980; since then, OHC has increased fairly steadily and, since 1990, has increasingly involved deeper layers of the ocean. In addition,OHC changes in sixmajor oceans are reliable on decadal timescales. All ocean basins examined have experienced significant warming since 1998, with the greatest warming in the southern oceans, the tropical/subtropical Pacific Ocean, and the tropical/subtropical Atlantic Ocean. This new look at OHC and EEI changes over time provides greater confidence than previously possible, and the data sets produced are a valuable resource for further study.},
doi = {10.1126/sciadv.1601545},
journal = {Science Advances},
number = 3,
volume = 3,
place = {United States},
year = {Fri Mar 10 00:00:00 EST 2017},
month = {Fri Mar 10 00:00:00 EST 2017}
}

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  • Greenhouse-gas emissions have created a planetary energy imbalance that is primarily manifested by increasing ocean heat content (OHC). Updated observational estimates of full-depth OHC change since 1970 are presented that account for recent advancements in reducing observation errors and biases. The full-depth OHC has increased by 0.74 [0.68, 0.80]  ×  10 22 J yr −1 (0.46 Wm −2) and 1.22 [1.16–1.29]  ×  10 22 J yr −1 (0.75 Wm −2) for 1970–2005 and 1992–2005, respectively, with a 5 to 95 % confidence interval of the median. The CMIP5 models show large spread in OHC changes, suggesting that some models are not state-of-the-art and require further improvements. However, the ensemble median hasmore » excellent agreement with our observational estimate: 0.68 [0.54–0.82]  ×  10 22 J yr −1 (0.42 Wm −2) from 1970 to 2005 and 1.25 [1.10–1.41]  ×  10 22 J yr −1 (0.77 Wm −2) from 1992 to 2005. These results increase confidence in both the observational and model estimates to quantify and study changes in Earth's energy imbalance over the historical period. We suggest that OHC be a fundamental metric for climate model validation and evaluation, especially for forced changes (decadal timescales).« less
    Cited by 4
  • Here, greenhouse-gas emissions have created a planetary energy imbalance that is primarily manifested by increasing ocean heat content (OHC). Updated observational estimates of full-depth OHC change since 1970 are presented that account for recent advancements in reducing observation errors and biases. The full-depth OHC has increased by 0.74 [0.68, 0.80] × 10 22 J yr –1 (0.46 Wm –2) and 1.22 [1.16–1.29] × 10 22 J yr –1 (0.75 Wm –2) for 1970–2005 and 1992–2005, respectively, with a 5 to 95 % confidence interval of the median. The CMIP5 models show large spread in OHC changes, suggesting that some modelsmore » are not state-of-the-art and require further improvements. However, the ensemble median has excellent agreement with our observational estimate: 0.68 [0.54–0.82] × 10 22 J yr –1 (0.42 Wm –2) from 1970 to 2005 and 1.25 [1.10–1.41] × 10 22 J yr –1 (0.77 Wm –2) from 1992 to 2005. These results increase confidence in both the observational and model estimates to quantify and study changes in Earth's energy imbalance over the historical period. We suggest that OHC be a fundamental metric for climate model validation and evaluation, especially for forced changes (decadal timescales).« less
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