Estimating Global Ocean Heat Content Changes in the Upper 1800 m since 1950 and the Influence of Climatology Choice*

2014 ◽  
Vol 27 (5) ◽  
pp. 1945-1957 ◽  
Author(s):  
John M. Lyman ◽  
Gregory C. Johnson
Keyword(s):  
Heat Content ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Ocean Temperature ◽  
Vertical Separation ◽  
Ocean Heat Uptake ◽  
Expendable Bathythermograph ◽  
Heat Uptake ◽  
The Mean

Abstract Ocean heat content anomalies are analyzed from 1950 to 2011 in five distinct depth layers (0–100, 100–300, 300–700, 700–900, and 900–1800 m). These layers correspond to historic increases in common maximum sampling depths of ocean temperature measurements with time, as different instruments—mechanical bathythermograph (MBT), shallow expendable bathythermograph (XBT), deep XBT, early sometimes shallower Argo profiling floats, and recent Argo floats capable of worldwide sampling to 2000 m—have come into widespread use. This vertical separation of maps allows computation of annual ocean heat content anomalies and their sampling uncertainties back to 1950 while taking account of in situ sampling advances and changing sampling patterns. The 0–100-m layer is measured over 50% of the globe annually starting in 1956, the 100–300-m layer starting in 1967, the 300–700-m layer starting in 1983, and the deepest two layers considered here starting in 2003 and 2004, during the implementation of Argo. Furthermore, global ocean heat uptake estimates since 1950 depend strongly on assumptions made concerning changes in undersampled or unsampled ocean regions. If unsampled areas are assumed to have zero anomalies and are included in the global integrals, the choice of climatological reference from which anomalies are estimated can strongly influence the global integral values and their trend: the sparser the sampling and the bigger the mean difference between climatological and actual values, the larger the influence.

The Annual Cycle of the Energy Budget. Part I: Global Mean and Land–Ocean Exchanges

2008 ◽  
Vol 21 (10) ◽  
pp. 2297-2312 ◽  
Author(s):  
John T. Fasullo ◽  
Kevin E. Trenberth
Keyword(s):  
Energy Budget ◽  
Annual Cycle ◽  
Radiant Energy ◽  
Heat Content ◽  
Ocean Heat Content ◽  
Radiation Budget ◽  
Global Ocean ◽  
Net Radiation ◽  
Community Land Model ◽  
The Mean

Abstract The mean and annual cycle of energy flowing into the climate system and its storage, release, and transport in the atmosphere, ocean, and land surface are estimated with recent observations. An emphasis is placed on establishing internally consistent quantitative estimates with discussion and assessment of uncertainty. At the top of the atmosphere (TOA), adjusted radiances from the Earth Radiation Budget Experiment (ERBE) and Clouds and the Earth’s Radiant Energy System (CERES) are used, while in the atmosphere the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis and 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) estimates are used. The net upward surface flux (FS) over ocean is derived as the residual of the TOA and atmospheric energy budgets, and is compared with direct calculations of ocean heat content (OE) and its tendency (δOE/δt) from several ocean temperature datasets. Over land, FS from a stand-alone simulation of the Community Land Model forced by observed fields is used. A depiction of the full energy budget based on ERBE fluxes from 1985 to 1989 and CERES fluxes from 2000 to 2004 is constructed that matches estimates of the global, global ocean, and global land imbalances. In addition, the annual cycle of the energy budget during both periods is examined and compared with ocean heat content changes. The near balance between the net TOA radiation (RT) and FS over ocean and thus with OE, and between RT and atmospheric total energy divergence over land, are documented both in the mean and for the annual cycle. However, there is an annual mean transport of energy by the atmosphere from ocean to land regions of 2.2 ± 0.1 PW (1 PW = 1015 W) primarily in the northern winter when the transport exceeds 5 PW. The global albedo is dominated by a semiannual cycle over the oceans, but combines with the large annual cycle in solar insolation to produce a peak in absorbed solar and net radiation in February, somewhat after the perihelion, and with the net radiation 4.3 PW higher than the annual mean, as it is enhanced by the annual cycle of outgoing longwave radiation that is dominated by land regions. In situ estimates of the annual variation of OE are found to be unrealistically large. Challenges in diagnosing the interannual variability in the energy budget and its relationship to climate change are identified in the context of the episodic and inconsistent nature of the observations.

Historical ocean heat uptake in CMIP6 Earth System models: global and regional perspectives

2020 ◽  
Author(s):  
Till Kuhlbrodt ◽  
Aurore Voldoire ◽  
Matthew Palmer ◽  
Rachel Killick ◽  
Colin Jones
Keyword(s):  
Time Series ◽  
Climate Models ◽  
Global Climate ◽  
Heat Content ◽  
Global Ocean ◽  
Earth System ◽  
Ocean Heat Uptake ◽  
The Pacific ◽  
Heat Uptake ◽  
Earth System Models

<p>Ocean heat content is arguably one of the most relevant metrics for tracking global climate change and in particular the current global heating. Because of its enormous heat capacity, the global ocean stores about 93 percent of the excess heat in the Earth System. Time series of global ocean heat content (OHC) closely track Earth’s energy imbalance as observed as the net radiative balance at the top of the atmosphere. For these reasons simulated OHC time series are a cornerstone for assessing the scientific performance of Earth System models (ESM) and global climate models. Here we present a detailed analysis of the OHC change in simulations of the historical climate (20<sup>th</sup> century up to 2014) performed with four of the current, state-of-the art generation of ESMs and climate models. These four models are UKESM1, HadGEM3-GC3.1-LL, CNRM-ESM2-1 and CNRM-CM6-1. All four share the same ocean component, NEMO3.6 in the shaconemo eORCA1 configuration, and they all take part in CMIP6, the current Phase 6 of the Coupled Model Intercomparison Project. Analysing a small number of models gives us the opportunity to analyse OHC change for the global ocean as well as for individual ocean basins. In addition to the ensemble means, we focus on some individual ensemble members for a more detailed process understanding. For the global ocean, the two CNRM models reproduce the observed OHC change since the 1960s closely, especially in the top 700 m of the ocean. The two UK models (UKESM1 and HadGEM3-GC3.1-LL) do not simulate the observed global ocean warming in the 1970s and 1980s, and they warm too fast after 1991. We analyse how this varied performance across the models relates to the simulated radiative forcing of the atmosphere. All four models show a smaller ocean heat uptake since 1971, and a larger transient climate response (TCR), than the CMIP5 ensemble mean. Close analysis of a few individual ensemble members indicates a dominant role of heat uptake and deep-water formation processes in the Southern Ocean for variability and change in global OHC. Evaluating OHC change in individual ocean basins reveals that the lack of warming in the UK models stems from the Pacific and Indian basins, while in the Atlantic the OHC change 1971-2014 is close to the observed value. Resolving the ocean warming in depth and time shows that regional ocean heat uptake in the North Atlantic plays a substantial role in compensating small warming rates elsewhere. An opposite picture emerges from the CNRM models. Here the simulated OHC change is close to observations in the Pacific and Indian basins, while tending to be too small in the Atlantic, indicating a markedly different role for the Atlantic meridional overturning circulation (AMOC) and cross-equatorial heat transport in these models.</p>

scholarly journals A review of global ocean temperature observations: Implications for ocean heat content estimates and climate change

2013 ◽  
Vol 51 (3) ◽  
pp. 450-483 ◽  
Author(s):  
J. P. Abraham ◽  
M. Baringer ◽  
N. L. Bindoff ◽  
T. Boyer ◽  
L. J. Cheng ◽  
...  
Keyword(s):  
Climate Change ◽  
Heat Content ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Ocean Temperature ◽  
Temperature Observations

Recent trajectory of ocean heat uptake estimated from novel 1972-2017 ocean sea-ice model hindcast simulations

2021 ◽  
Author(s):  
Maurice Huguenin ◽  
Ryan Holmes ◽  
Matthew England
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Heat Content ◽  
Anthropogenic Heat ◽  
Global Ocean ◽  
Ocean Heat Uptake ◽  
Heat Uptake ◽  
The Tropics ◽  
And Storage ◽  
Ice Model

<p>Uptake and storage of heat by the ocean plays a critical role in modulating the Earth's climate system. In the last 50 years, the ocean has absorbed over 90% of the additional energy accumulating in the Earth system due to radiative imbalance. However, our knowledge about ocean heat uptake (OHU), transport and storage is strongly constrained by the sparse observational record with large uncertainties. In this study, we conduct a suite of historical 1972–2017 hindcast simulations using a global ocean-sea ice model that are specifically designed to account for a cold start climate and model drift. The hindcast simulations are initialised from an equilibrated control simulation that uses repeat decade forcing over the period 1962-1971. This repeat decade forcing approach is a compromise between an early unobserved period (where our confidence in the forcing is low) and later periods (which would result in a shorter experiment period and a smaller fraction of the total OHU). The simulations are aimed at giving a good estimate of the trajectory of OHU in the tropics, the extratropics and individual ocean basins in recent decades. Many modelling studies that look at recent OHU rates so far use a simpler approach for the forcing. For example, they use repeating cycles of 1950-2010 Coordinated Ocean Reference Experiment (CORE) forcing that is consistent with the Ocean Model Intercomparison Project 2 (OMIP-2). However, this approach cannot account for model drift. The new simulations here highlight the dominant role of the extratropics, and in particular the Southern Ocean in OHU. In contrast, little heat is absorbed in the tropics and simulations forced with only tropical trends in atmospheric forcing show only weak global ocean heat content trends. Almost 50% of the heat taken up from the atmosphere in the Southern Ocean is transported into the Atlantic Ocean. Two-thirds of this Southern Ocean-sourced heat is then subsequently lost to the atmosphere in the North Atlantic but nevertheless this basin gains heat overall. Our results help to estimate the large-scale cycling of anthropogenic heat within the ocean today and have implications for heat content trends under a changing climate.</p>

scholarly journals In Situ–Based Reanalysis of the Global Ocean Temperature and Salinity with ISAS: Variability of the Heat Content and Steric Height

2016 ◽  
Vol 29 (4) ◽  
pp. 1305-1323 ◽  
Author(s):  
Fabienne Gaillard ◽  
Thierry Reynaud ◽  
Virginie Thierry ◽  
Nicolas Kolodziejczyk ◽  
Karina von Schuckmann
Keyword(s):  
Southern Ocean ◽  
World Ocean ◽  
Heat Content ◽  
Absolute Error ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Analysis Tool ◽  
Steric Height ◽  
The Impact

Abstract The In Situ Analysis System (ISAS) was developed to produce gridded fields of temperature and salinity that preserve as much as possible the time and space sampling capabilities of the Argo network of profiling floats. Since the first global reanalysis performed in 2009, the system has evolved, and a careful delayed-mode processing of the 2002–12 dataset has been carried out using version 6 of ISAS and updating the statistics to produce the ISAS13 analysis. This last version is now implemented as the operational analysis tool at the Coriolis data center. The robustness of the results with respect to the system evolution is explored through global quantities of climatological interest: the ocean heat content and the steric height. Estimates of errors consistent with the methodology are computed. This study shows that building reliable statistics on the fields is fundamental to improve the monthly estimates and to determine the absolute error bars. The new mean fields and variances deduced from the ISAS13 reanalysis and dataset show significant changes relative to the previous ISAS estimates, in particular in the Southern Ocean, justifying the iterative procedure. During the decade covered by Argo, the intermediate waters appear warmer and saltier in the North Atlantic and fresher in the Southern Ocean than in World Ocean Atlas 2005 long-term mean. At interannual scale, the impact of ENSO on the ocean heat content and steric height is observed during the 2006/07 and 2009/10 events captured by the network.

scholarly journals An Ensemble Observing System Simulation Experiment of Global Ocean Heat Content Variability

2017 ◽  
Author(s):  
Arin D. Nelson ◽  
Jeffrey B. Weiss ◽  
Baylor Fox-Kemper ◽  
Royce K. P. Zia ◽  
Fabienne Gaillard
Keyword(s):  
System Simulation ◽  
Heat Content ◽  
Natural Variability ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Climate System Model ◽  
Analysis System ◽  
One Year ◽  
Mean Square Errors

Abstract. We quantify skill and uncertainty in observing the statistics of natural variability using observing system simulation experiments on an ensemble of climate simulations and an observing strategy of in situ measurements and objective mapping. The targeted statistic is the 0–700 m global ocean heat content anomaly as observed by the In Situ Analysis System 2013 (ISAS13) strategy of a long, equilibriated simulation of the Community Climate System Model (CCSM) version 3.5. Subannual variability is found to be significantly contaminated by the observing strategy, especially before 2005, primarily due to the sparseness and seasonality in the number and location of pre-Argo observations. However, one-year running means from 2005 onward are found to faithfully capture the natural variability of the model's true ocean heat content variability. During these years, synthetic observed annual running means are strongly correlated with the actual annual running means of the model, with a median correlation of 95 %, versus only 60 % for the observational record before 2005. When scaled to account for the fact that the real ocean is more variable than the model, root mean square errors in observing the annual-running mean natural variability of the global ocean heat content are estimated to be 6.2 ZJ for the pre-Argo era (1990–2005) and 2.1 ZJ for the Argo era (2005–2013) with relative signal-to-noise ratios of 1.9 and 14.7. Combining the estimated, scaled uncertainties of the observing strategy with its estimated trend, the 1990–2013 trend in global ocean heat content is found to be 5.3 ± 1.0 ZJ/yr.

A new project to monitor the Ocean Heat Content and the Earth Energy imbalance from space: MOHeaCAN

2020 ◽  
Author(s):  
Michaël Ablain ◽  
Benoit Meyssignac ◽  
Alejandro Blazquez ◽  
Marti Florence ◽  
Rémi Jugier ◽  
...  
Keyword(s):  
Time Scales ◽  
Radiant Energy ◽  
Heat Content ◽  
Deep Ocean ◽  
Heat Fluxes ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Energy Imbalance ◽  
The Earth

<p>The Earth Energy Imbalance (EEI) is a key indicator to understand the Earth’s changing. However, measuring this indicator is challenging since it is a globally integrated variable whose variations are small, of the order of several tenth of W.m-2, compared to the amount of energy entering and leaving the climate system of ~340 W.m-2. Recent studies suggest that the EEI response to anthropogenic GHG and aerosols emissions is 0.5-1 W.m-2. It implies that an accuracy of <0.3 W.m-2 at decadal time scales is necessary to evaluate the long term mean EEI associated with anthropogenic forcing. Ideally an accuracy of <0.1 W.m-2 at decadal time scales is desirable if we want to monitor future changes in EEI. The ocean heat content (OHC) is a very good proxy to estimate EEI as ocean concentrates the vast majority of the excess of energy (~93%) associated with EEI. Several methods exist to estimate OHC:</p><ul><li>the direct measurement of in situ temperature based on temperature/Salinity profiles (e.g. ARGO floats),</li> <li>the measurement of the net ocean surface heat fluxes from space (CERES),</li> <li>the estimate from ocean reanalyses that assimilate observations from both satellite and in situ instruments,</li> <li>the measurement of the thermal expansion of the ocean from space based on differences between the total sea-level content derived from altimetry measurements and the mass content derived from GRACE data (noted “Altimetry-GRACE”).</li> </ul><p>To date, the best results are given by the first method based on ARGO network. However ARGO measurements do no sample deep ocean below 2000 m depth and marginal seas as well as the ocean below sea ice. Re-analysis provides a more complete estimation but large biases in the polar oceans and spurious drifts in the deep ocean mask a significant part of the OHC signal related to EEI. The method based on estimation of ocean net heat fluxes (CERES) is not appropriate for OHC calculation due to a too strong uncertainty (±15 W.m-2). </p><p>In the MOHeaCAN project supported by ESA, we are being developed the “Altimetry-GRACE” approach  which is promising since it provides consistent spatial and temporal sampling of the ocean, it samples the entire global ocean, except for polar regions, and it provides estimates of the OHC over the ocean’s entire depth. Consequently, it complements the OHC estimation from ARGO.  However, to date the uncertainty in OHC from this method is close to 0.5 W.m-2, and thus greater than the requirement of 0.3 W.m-2 needed to a good EEI estimation. Therefore the scientific objective of the MOHeaCan project is  to improve these estimates :</p><ol><li>by developing novel algorithms in order to reach the challenging target for the uncertainty quantification of 0.3 W. m−2;</li> <li>by estimating realistic OHC uncertainties thanks to an error budget of measurements applying a rigorous mathematical formalism;</li> <li>by developing a software prototype systems that allow to perform sensitivities studies and OHC product and its uncertainty generation;</li> <li>by assessing our estimation by performing comparison against independent estimates based on ARGO network, and based on the Clouds and the Earth’s Radiant energy System (CERES) measurements at the top of the atmosphere.</li> </ol>

scholarly journals Global representation of tropical cyclone-induced ocean thermal changes using Argo data – Part 2: Estimating air–sea heat fluxes and ocean heat content changes

2014 ◽  
Vol 11 (6) ◽  
pp. 2907-2937
Author(s):  
L. Cheng ◽  
J. Zhu ◽  
R. L. Sriver
Keyword(s):  
Heat Loss ◽  
Heat Budget ◽  
Heat Content ◽  
Global Scale ◽  
Heat Fluxes ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Storm Events ◽  
Argo Data ◽  
Ocean Heat Uptake

Abstract. We use Argo temperature data to examine changes in ocean heat content (OHC) and air–sea heat fluxes induced by tropical cyclones (TC)s on a global scale. A footprint technique that analyzes the vertical structure of cross-track thermal responses along all storm tracks during the period 2004–2012 is utilized (see part I). We find that TCs are responsible for 1.87 PW (11.05 W m−2 when averaging over the global ocean basin) of heat transfer annually from the global ocean to the atmosphere during storm passage (0–3 days) on a global scale. Of this total, 1.05 ± 0.20 PW (4.80 ± 0.85 W m−2) is caused by Tropical storms/Tropical depressions (TS/TD) and 0.82 ± 0.21 PW (6.25 ± 1.5 W m−2) is caused by hurricanes. Our findings indicate that ocean heat loss by TCs may be a substantial missing piece of the global ocean heat budget. Net changes in OHC after storm passage is estimated by analyzing the temperature anomalies during wake recovery following storm events (4–20 days after storm passage) relative to pre-storm conditions. Results indicate the global ocean experiences a 0.75 ± 0.25 PW (5.98 ± 2.1W m−2) net heat gain annually for hurricanes. In contrast, under TS/TD conditions, ocean experiences 0.41 ± 0.21 PW (1.90 ± 0.96 W m−2) net ocean heat loss, suggesting the overall oceanic thermal response is particularly sensitive to the intensity of the event. The net ocean heat uptake caused by all storms is 0.34 PW.

scholarly journals Ocean Heat Uptake and Interbasin Transport of the Passive and Redistributive Components of Surface Heating

2016 ◽  
Vol 29 (20) ◽  
pp. 7507-7527 ◽  
Author(s):  
Oluwayemi A. Garuba ◽  
Barry A. Klinger
Keyword(s):  
Heat Flux ◽  
Heat Input ◽  
Surface Heat Flux ◽  
Heat Content ◽  
Surface Heat ◽  
Global Ocean ◽  
Passive Component ◽  
Ocean Heat Uptake ◽  
Anomalous Surface ◽  
Heat Uptake

Abstract Global warming induces ocean circulation changes that not only can redistribute ocean reservoir temperature stratification but also change the total heat content anomaly of the ocean. Here all consequences of this process are referred to collectively as “redistribution.” Previous model studies of redistributive effects could not measure the net global contribution to the amount of ocean heat uptake by redistribution. In this study, a global ocean model experiment with abrupt increase in surface temperature is conducted with a new passive tracer formulation. This separates ocean heat uptake into contributions due to redistribution temperature and surface heat flux anomalies and those due to the passive advection and mixing of surface heat flux anomalies forced in the atmosphere. For a decline in the Atlantic meridional overturning circulation of about 40%, redistribution nearly doubles the Atlantic passive anomalous surface heat input and depth penetration of temperature anomalies. However, smaller increases in the Indian and Pacific Oceans cause the net global redistributive contribution to be only 25% of the passive contribution. Despite the much larger anomalous surface heat input in the Atlantic, the Pacific gains heat content anomaly similar to that in the Atlantic because of export from the Atlantic and Indian Oceans via the global conveyor belt. Of this interbasin heat transport, most of the passive component comes from the Indian Ocean and the redistributive component comes from the Atlantic.

scholarly journals Impact of Tropical Cyclones on the Global Ocean: Results from Multidecadal Global Ocean Simulations Isolating Tropical Cyclone Forcing

2018 ◽  
Vol 31 (21) ◽  
pp. 8761-8784 ◽  
Author(s):  
Hui Li ◽  
Ryan L. Sriver
Keyword(s):  
High Resolution ◽  
Tropical Cyclone ◽  
Heat Transport ◽  
Time Scales ◽  
Heat Content ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Multiple Time Scales ◽  
Ocean Temperature ◽  
Earth System

Tropical cyclone (TC)-induced ocean vertical mixing can alter the upper-ocean temperature structure, influencing ocean heat content variability and meridional ocean heat transport. TC–ocean interactions can influence tropical variability on seasonal to interannual time scales. Here the impacts of TCs on the global ocean and the associated feedbacks are investigated using a hierarchy of high-resolution global ocean model simulations featuring the Community Earth System Model (CESM). The aim is to understand the potential impact of the model’s self-generated transient TC events on the modeled global ocean. Two ocean-only simulations are performed using the atmosphere boundary conditions from a fully coupled preindustrial CESM simulation configured with 0.25° atmosphere resolution and the nominal 1° ocean resolution (with ~0.25° meridional resolution in the tropics). The high-resolution coupled model is capable of directly simulating TC events with wind structure and climatology generally consistent with observations. TC effects at the ocean–atmosphere boundary are filtered out in one of the ocean simulations (OCN_FILT) while fully retained in the other (OCN_TC) in order to isolate the effect of the TCs on regional and global ocean variability across multiple time scales (from intraseasonal to interdecadal). Results show that the model-simulated TCs can 1) alter surface and subsurface ocean temperature patterns and variability; 2) affect ocean energetics, including increasing ocean mixed layer depth and strengthening subtropical gyre and meridional overturning circulations; and 3) influence ocean meridional heat transport and ocean heat content from seasonal to interannual time scales. Results help provide insights into the model behavior and the physical nature of the effect of TCs within the Earth system.

Sign in / Sign up

Export Citation Format

Share Document