scholarly journals Change of the Global Ocean Vertical Heat Transport over 1993–2010

2017 ◽  
Vol 30 (14) ◽  
pp. 5319-5327 ◽  
Author(s):  
Xinfeng Liang ◽  
Christopher G. Piecuch ◽  
Rui M. Ponte ◽  
Gael Forget ◽  
Carl Wunsch ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Exchange ◽  
Heat Transport ◽  
Heat Content ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Mixing Processes ◽  
State Estimate ◽  
Vertical Heat ◽  
Vertical Heat Flux

A dynamically and data-consistent ocean state estimate during 1993–2010 is analyzed for bidecadal changes in the mechanisms of heat exchange between the upper and lower oceans. Many patterns of change are consistent with prior studies. However, at various levels above 1800 m the global integral of the change in ocean vertical heat flux involves the summation of positive and negative regional contributions and is not statistically significant. The nonsignificance of change in the global ocean vertical heat transport from an ocean state estimate that provides global coverage and regular sampling, spatially and temporally, raises the question of whether an adequate observational database exists to assess changes in the upper ocean heat content over the past few decades. Also, whereas the advective term largely determines the spatial pattern of the change in ocean vertical heat flux, its global integral is not significantly different from zero. In contrast, the diffusive term, although regionally weak except in high-latitude oceans, produces a statistically significant extra downward heat flux during the 2000s. This result suggests that besides ocean advection, ocean mixing processes, including isopycnal and diapycnal as well as convective mixing, are important for the decadal variation of the heat exchange between upper and deep oceans as well. Furthermore, the analyses herein indicate that focusing on any particular region in explaining changes of the global ocean heat content is misleading.

scholarly journals Vertical Redistribution of Oceanic Heat Content

2015 ◽  
Vol 28 (9) ◽  
pp. 3821-3833 ◽  
Author(s):  
Xinfeng Liang ◽  
Carl Wunsch ◽  
Patrick Heimbach ◽  
Gael Forget
Keyword(s):  
Heat Flux ◽  
Heat Exchange ◽  
Heat Transport ◽  
Heat Content ◽  
Deep Ocean ◽  
Temporal Variations ◽  
Near Surface ◽  
Carbon 14 ◽  
Vertical Heat ◽  
Vertical Heat Flux

Abstract Estimated values of recent oceanic heat uptake are on the order of a few tenths of a W m−2, and are a very small residual of air–sea exchanges, with annual average regional magnitudes of hundreds of W m−2. Using a dynamically consistent state estimate, the redistribution of heat within the ocean is calculated over a 20-yr period. The 20-yr mean vertical heat flux shows strong variations in both the lateral and vertical directions, consistent with the ocean being a dynamically active and spatially complex heat exchanger. Between mixing and advection, the two processes determining the vertical heat transport in the deep ocean, advection plays a more important role in setting the spatial patterns of vertical heat exchange and its temporal variations. The global integral of vertical heat flux shows an upward heat transport in the deep ocean, suggesting a cooling trend in the deep ocean. These results support an inference that the near-surface thermal properties of the ocean are a consequence, at least in part, of internal redistributions of heat, some of which must reflect water that has undergone long trajectories since last exposure to the atmosphere. The small residual heat exchange with the atmosphere today is unlikely to represent the interaction with an ocean that was in thermal equilibrium at the start of global warming. An analogy is drawn with carbon-14 “reservoir ages,” which range from over hundreds to a thousand years.

scholarly journals Comparison of ocean heat content from two eddy-resolving hindcast simulations with OFES1 and OFES2

2021 ◽  
Author(s):  
Fanglou Liao ◽  
Xiao Hua Wang ◽  
Zhiqiang Liu
Keyword(s):  
Heat Transport ◽  
General Circulation ◽  
Large Scale ◽  
Potential Temperature ◽  
Heat Content ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Spatial Distributions

Abstract. The ocean heat content (OHC) estimates from high-resolution hindcast simulations from the Ocean General Circulation Model for the Earth Simulator Version 1 (OFES1) and Version 2 (OFES2), and a global objective analysis of subsurface temperature observations (EN4.2.1) were compared. There was an OHC increase in most of the global ocean over a 57-year period, mainly a result of vertical displacements of neutral density surfaces. However, we found substantial differences in the temporal and meridional distributions of the OHC between the two OFES hindcasts. The spatial distributions of potential-temperature change also differed significantly, especially in the Atlantic Ocean. The spatial distributions of the time-averaged surface heat flux and heat transport from the OFES1 and OFES2 were highly correlated, but differences could be seen. However, these differences, more specifically in the heat transport, were only partially responsible for the OHC differences. The marked OHC differences may arise from the different vertical mixing schemes and may impact the large-scale pressure field, and thus the geostrophic current. The work here should be a useful reference for future OFES users.

scholarly journals ENSO-Related Global Ocean Heat Content Variations

2018 ◽  
Vol 32 (1) ◽  
pp. 45-68 ◽  
Author(s):  
Quran Wu ◽  
Xuebin Zhang ◽  
John A. Church ◽  
Jianyu Hu
Keyword(s):  
Heat Exchange ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Heat Content ◽  
Vertical Direction ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Ocean Current ◽  
Enso Events

Abstract The modulation of the full-depth global integrated ocean heat content (GOHC) by El Niño–Southern Oscillation (ENSO) has been estimated in various studies. However, the quantitative results and the mechanisms at work remain uncertain. Here, a dynamically consistent ocean state estimate is utilized to study the large-scale integrated heat content variations during ENSO events for the global ocean. The full-depth GOHC exhibits a cooling tendency during the peak and decaying phases of El Niño, which is a result of the negative surface heat flux (SHF) anomaly in the tropics (30°S–30°N), partially offset by the positive SHF anomaly at higher latitudes. The tropical SHF anomaly acts as a lagged response to damp the convergence of oceanic heat transport, which redistributes heat from the extratropics and the subsurface layers (100–440 m) into the upper tropical oceans (0–100 m) during the onset and peak of El Niño. These results highlight the global nature of the oceanic heat redistribution during ENSO events, as well as how the redistribution process affects the full-depth GOHC. The meridional heat exchange across 30°S and 30°N is driven by ocean current anomalies, while multiple processes contribute to the vertical heat exchange across 100 m simultaneously. Heat advection due to unbalanced mass transport is distinguished from the mass balanced one, with significant contributions from the meridional and zonal overturning cells being identified for the latter in the vertical direction. Results presented here have implications for monitoring the planetary energy budget and evaluating ENSO’s global imprints on ocean heat content in different estimates.

Bounds on the convective heat transport in containers

2001 ◽  
Vol 431 ◽  
pp. 427-432 ◽  
Author(s):  
RODNEY A. WORTHING
Keyword(s):  
Heat Flux ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Heat Transport ◽  
Convective Heat ◽  
Upper Bounds ◽  
Vertical Heat ◽  
Vertical Heat Flux

Using the Hopf–Doering–Constantin decomposition, we derive upper bounds on the vertical heat flux in closed containers. It is found that the original bound of Doering & Constantin (1996) for Nusselt number as a function of Rayleigh number, Nu [ges ] √R/4, holds, at the very least, asymptotically as R → ∞ under reasonably diverse experimental settings.

scholarly journals Budgets for Decadal Variability in Pacific Ocean Heat Content

2020 ◽  
Vol 33 (17) ◽  
pp. 7663-7678
Author(s):  
Zeyuan Hu ◽  
Aixue Hu ◽  
Yongyun Hu ◽  
Nan Rosenbloom
Keyword(s):  
Heat Flux ◽  
Pacific Ocean ◽  
Heat Transport ◽  
Surface Heat Flux ◽  
Heat Content ◽  
Surface Heat ◽  
Equatorial Pacific ◽  
Ocean Heat Content ◽  
Heat Advection ◽  
Oceanic Heat Transport

AbstractA slowdown in the rate of surface warming in the early 2000s led to renewed interest in the redistribution of ocean heat content (OHC) and its relationship with internal climate variability. We use the Community Earth System Model version 1 to study the relationship between OHC and the interdecadal Pacific oscillation (IPO), a major mode of decadal sea surface temperature variability in the Pacific Ocean. By comparing the relative contributions of surface heat flux and ocean dynamics to changes in OHC for different phases of the IPO, we try to identify the underlying physical processes involved. Our results suggest that during IPO phase transitions, changes of 0–300-m OHC across the northern extratropical Pacific are positively contributed by both surface heat flux and oceanic heat transport. By contrast, oceanic heat transport appears to drive the OHC changes in equatorial Pacific whereas surface heat flux acts as a damping term. During a positive IPO phase, weakened wind-driven circulation acts to increase the OHC in the equatorial Pacific while the enhanced evaporation acts to damp OHC anomalies. In the Kuroshio–Oyashio Extension region, a dipole anomaly of zonal heat advection amplifies an OHC dipole anomaly that moves eastward, while strong turbulent heat fluxes act to dampen this OHC anomaly. In the northern subtropical Pacific, both the wind-driven evaporation change and the change of zonal heat advection along Kuroshio Extension contribute to the OHC change during phase transition. For the northern subpolar Pacific, both surface heat flux and enhanced meridional advection contribute to the positive OHC anomalies during the positive IPO phase.

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.

scholarly journals 20th century cooling of the deep ocean contributed to delayed acceleration of Earth’s energy imbalance

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
A. Bagnell ◽  
T. DeVries
Keyword(s):  
20Th Century ◽  
Heat Content ◽  
Deep Ocean ◽  
Ocean Warming ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Energy Imbalance ◽  
Delayed Onset ◽  
The Past ◽  
Historical Reconstructions

AbstractThe historical evolution of Earth’s energy imbalance can be quantified by changes in the global ocean heat content. However, historical reconstructions of ocean heat content often neglect a large volume of the deep ocean, due to sparse observations of ocean temperatures below 2000 m. Here, we provide a global reconstruction of historical changes in full-depth ocean heat content based on interpolated subsurface temperature data using an autoregressive artificial neural network, providing estimates of total ocean warming for the period 1946-2019. We find that cooling of the deep ocean and a small heat gain in the upper ocean led to no robust trend in global ocean heat content from 1960-1990, implying a roughly balanced Earth energy budget within −0.16 to 0.06 W m−2 over most of the latter half of the 20th century. However, the past three decades have seen a rapid acceleration in ocean warming, with the entire ocean warming from top to bottom at a rate of 0.63 ± 0.13 W m−2. These results suggest a delayed onset of a positive Earth energy imbalance relative to previous estimates, although large uncertainties remain.

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.

scholarly journals On Anomalous Ocean Heat Transport toward the Arctic and Associated Climate Predictability

2016 ◽  
Vol 29 (2) ◽  
pp. 689-704 ◽  
Author(s):  
Marius Årthun ◽  
Tor Eldevik
Keyword(s):  
Heat Transport ◽  
Air Temperature ◽  
Time Scale ◽  
Heat Content ◽  
Surface Air Temperature ◽  
Meridional Overturning Circulation ◽  
Ocean Heat Content ◽  
The Arctic ◽  
Ocean Heat Transport ◽  
Climate Predictability

Abstract A potential for climate predictability is rooted in anomalous ocean heat transport and its consequent influence on the atmosphere above. Here the propagation, drivers, and atmospheric impact of heat anomalies within the northernmost limb of the Atlantic meridional overturning circulation are assessed using a multicentury climate model simulation. Consistent with observation-based inferences, simulated heat anomalies propagate from the eastern subpolar North Atlantic into and through the Nordic seas. The dominant time scale of associated climate variability in the northern seas is 14 years, including that of observed sea surface temperature and modeled ocean heat content, air–sea heat flux, and surface air temperature. A heat budget analysis reveals that simulated ocean heat content anomalies are driven by poleward ocean heat transport, primarily related to variable volume transport. The ocean’s influence on the atmosphere, and hence regional climate, is manifested in the model by anomalous ocean heat convergence driving subsequent changes in surface heat fluxes and surface air temperature. The documented northward propagation of thermohaline anomalies in the northern seas and their consequent imprint on the regional atmosphere—including the existence of a common decadal time scale of variability—detail a key aspect of eventual climate predictability.

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