Anthropogenic Warming of the Oceans: Observations and Model Results

2006 ◽  
Vol 19 (10) ◽  
pp. 1873-1900 ◽  
Author(s):  
David W. Pierce ◽  
Tim P. Barnett ◽  
Krishna M. AchutaRao ◽  
Peter J. Gleckler ◽  
Jonathan M. Gregory ◽  
...  
Keyword(s):  
Heat Flux ◽  
Surface Heat Flux ◽  
Climate Model ◽  
Heat Budget ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Anthropogenic Forcing ◽  
Model Version ◽  
Ocean Atmosphere ◽  
Longwave Flux

Abstract Observations show the oceans have warmed over the past 40 yr, with appreciable regional variation and more warming at the surface than at depth. Comparing the observations with results from two coupled ocean–atmosphere climate models [the Parallel Climate Model version 1 (PCM) and the Hadley Centre Coupled Climate Model version 3 (HadCM3)] that include anthropogenic forcing shows remarkable agreement between the observed and model-estimated warming. In this comparison the models were sampled at the same locations as gridded yearly observed data. In the top 100 m of the water column the warming is well separated from natural variability, including both variability arising from internal instabilities of the coupled ocean–atmosphere climate system and that arising from volcanism and solar fluctuations. Between 125 and 200 m the agreement is not significant, but then increases again below this level, and remains significant down to 600 m. Analysis of PCM’s heat budget indicates that the warming is driven by an increase in net surface heat flux that reaches 0.7 W m−2 by the 1990s; the downward longwave flux increases by 3.7 W m−2, which is not fully compensated by an increase in the upward longwave flux of 2.2 W m−2. Latent and net solar heat fluxes each decrease by about 0.6 W m−2. The changes in the individual longwave components are distinguishable from the preindustrial mean by the 1920s, but due to cancellation of components, changes in the net surface heat flux do not become well separated from zero until the 1960s. Changes in advection can also play an important role in local ocean warming due to anthropogenic forcing, depending on the location. The observed sampling of ocean temperature is highly variable in space and time, but sufficient to detect the anthropogenic warming signal in all basins, at least in the surface layers, by the 1980s.

scholarly journals Heat Budget of the Upper Ocean in the South-Central Equatorial Pacific

2010 ◽  
Vol 23 (7) ◽  
pp. 1779-1792 ◽  
Author(s):  
Hailong Liu ◽  
Wuyin Lin ◽  
Minghua Zhang
Keyword(s):  
Heat Flux ◽  
Surface Energy ◽  
Mixed Layer ◽  
Surface Heat Flux ◽  
Heat Budget ◽  
Surface Heat ◽  
Central Pacific ◽  
South Central ◽  
Ocean Atmosphere ◽  
Global Datasets

Abstract The double intertropical convergence zone (ITCZ) over the tropical Pacific, with a spurious band of maximum annual sea surface temperature (SST) south of the equator between 5°S and 10°S, is a chronic bias in coupled ocean–atmosphere models. This study focuses on a region of the double ITCZ in the central Pacific from 5°S to 10°S and 170°E to 150°W, where coupled models display the largest biases in precipitation, by deriving a best estimate of the mixed layer heat budget for the region. Seven global datasets of objectively analyzed surface energy fluxes and four ocean assimilation products are first compared and then evaluated against field measurements in adjacent regions. It was shown that the global datasets differ greatly in their net downward surface energy flux in this region, but they fall broadly into two categories: one with net downward heat flux of about 30 W m−2 and the other around 10 W m−2. Measurements from the adjacent Manus and Nauru sites of the Atmospheric Radiation Measurement Program (ARM), the Tropical Atmosphere Ocean (TAO) buoys, and the Tropical Ocean and Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE) are then used to show that the smaller value is more realistic. An energy balance of the mixed layer is finally presented for the region as primarily between warming from surface heat flux of 7 W m−2 and horizontal advective cooling in the zonal direction of about 5 W m−2, with secondary contributions from meridional and vertical advections, heat storage, and subgrid-scale mixing. The 7 W m−2 net surface heat flux consists of warming of 210 W m−2 from solar radiation and cooling of 53, 141, and 8 W m−2, respectively, from longwave radiation, latent heat flux, and sensible heat flux. These values provide an observational basis to further study the initial development of excessive precipitation in coupled climate models in the central Pacific.

scholarly journals Seasonality of Decadal Sea Surface Temperature Anomalies in the Northwestern Pacific

2006 ◽  
Vol 19 (12) ◽  
pp. 2953-2968 ◽  
Author(s):  
Takashi Mochizuki ◽  
Hideji Kida
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Mixed Layer ◽  
Surface Heat Flux ◽  
Heat Budget ◽  
Surface Heat ◽  
Sea Surface ◽  
Northwestern Pacific ◽  
Sst Anomaly

Abstract The seasonality of the decadal sea surface temperature (SST) anomalies and the related physical processes in the northwestern Pacific were investigated using a three-dimensional bulk mixed layer model. In the Kuroshio–Oyashio Extension (KOE) region, the strongest decadal SST anomaly was observed during December–February, while that of the central North Pacific occurred during February–April. From an examination of the seasonal heat budget of the ocean mixed layer, it was revealed that the seasonal-scale enhancement of the decadal SST anomaly in the KOE region was controlled by horizontal Ekman temperature transport in early winter and by vertical entrainment in autumn. The temperature transport by the geostrophic current made only a slight contribution to the seasonal variation of the decadal SST anomaly, despite controlling the upper-ocean thermal conditions on decadal time scales through the slow Rossby wave adjustment to the wind stress curl. When averaging over the entire KOE region, the contribution from the net sea surface heat flux was also no longer significantly detected. By examining the horizontal distributions of the local thermal damping rate, however, it was concluded that the wintertime decadal SST anomaly in the eastern KOE region was rather damped by the net sea surface heat flux. It was due to the fact that the anomalous local thermal damping of the SST anomaly resulting from the vertical entrainment in autumn was considerably strong enough to suppress the anomalous local atmospheric thermal forcing that acted to enhance the decadal SST anomaly.

scholarly journals Simulations of Processes Associated with the Fast Warming Rate of the Southern Midlatitude Ocean

2010 ◽  
Vol 23 (1) ◽  
pp. 197-206 ◽  
Author(s):  
Wenju Cai ◽  
Tim Cowan ◽  
Stuart Godfrey ◽  
Susan Wijffels
Keyword(s):  
Twentieth Century ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Heat Content ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Ekman Transport ◽  
Content Increase ◽  
Intergovernmental Panel ◽  
Zonal Distribution

Abstract Significant warming has occurred across many of the world’s oceans throughout the latter part of the twentieth-century. The increase in the oceanic heat content displays a considerable spatial difference, with a maximum in the 35°–50°S midlatitude band. The relative importance of wind and surface heat flux changes in driving the warming pattern is the subject of much debate. Using wind, oceanic temperature, and heat flux outputs from twentieth-century multimodel experiments, conducted for the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), the authors were able to reproduce the fast, deep warming in the midlatitude band; however, this warming is unable to be accounted for by local heat flux changes. The associated vertical structure and zonal distribution are consistent with a Sverdrup-type response to poleward-strengthening winds, with a poleward shift of the Southern Hemisphere (SH) supergyre and the Antarctic Circumpolar Current. However, the shift is not adiabatic and involves a net oceanic heat content increase over the SH, which can only be forced by changes in the net surface heat flux. Counterintuitively, the heat required for the fast, deep warming is largely derived from the surface heat fluxes south of 50°S, where the surface flux into the ocean is far larger than that of the midlatitude band. The heat south of 50°S is advected northward by an enhanced northward Ekman transport induced by the poleward-strengthening winds and penetrates northward and downward along the outcropping isopycnals to a depth of over 1000 m. However, because none of the models resolve eddies and given that eddy fluxes could offset the increase in the northward Ekman transport, the heat source for the fast, deep warming in the midlatitude band could be rather different in the real world.

scholarly journals Extratropical cyclone induced sea surface temperature anomalies in the 2013/14 winter

2019 ◽  
Author(s):  
Helen F. Dacre ◽  
Simon A. Josey ◽  
Alan L. M. Grant
Keyword(s):  
Heat Flux ◽  
North Atlantic ◽  
Surface Heat Flux ◽  
Cold Front ◽  
Winter Season ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Sea Surface ◽  
Extratropical Cyclones ◽  
Sst Cooling

Abstract. The 2013/14 winter averaged sea surface temperature (SST) was anomalously cool in the mid-North Atlantic region. This season was also unusually stormy with extratropical cyclones passing over the mid-North Atlantic every 3 days. However, the processes by which cyclones contribute towards seasonal SST anomalies are not fully understood. In this paper a cyclone identification and tracking method is combined with ECMWF atmosphere and ocean reanalysis fields to calculate cyclone-relative net surface heat flux anomalies and resulting SST changes. Anomalously large negative heat fluxes are located behind the cyclones cold front resulting in anomalous cooling up to 0.2 K/day when the cyclones are at maximum intensity. This extratropical cyclone induced cold wake extends along the cyclones cold front but is small compared to climatological variability. To investigate the potential cumulative effect of the passage of multiple cyclone induced SST cooling in the same location we calculate Earth-relative net surface heat flux anomalies and resulting SST changes for the 2013/2014 winter period. Anomalously large winter averaged negative heat fluxes occur in a zonally orientated band extending across the North Atlantic between 40–60° N. The anomaly associated with cyclones is estimated using a cyclone masking technique which encompasses each cyclone centre and its trailing cold front. North Atlantic extratropical cyclones in the 2013/14 winter season account for 78 % of the observed net surface heat flux in the mid- North Atlantic and net surface heat fluxes in the 2013/14 winter season account for 70 % of the observed cooling in the mid-North Atlantic. Thus extratropical cyclones play a major role in determining the extreme 2013/2014 winter season SST cooling.

scholarly journals Impact of Soil Moisture Data Resolution on Soil Moisture and Surface Heat Flux Estimates through Data Assimilation: A Case Study in the Southern Great Plains

2019 ◽  
Vol 20 (4) ◽  
pp. 715-730 ◽  
Author(s):  
Yang Lu ◽  
Jianzhi Dong ◽  
Susan C. Steele-Dunne
Keyword(s):  
Heat Flux ◽  
Soil Moisture ◽  
Spatial Resolution ◽  
Surface Heat Flux ◽  
Root Zone ◽  
Sampling Frequency ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Soil Moisture Data ◽  
Temporal Sampling

Abstract The spatial heterogeneity and temporal variation of soil moisture and surface heat fluxes are key to many geophysical and environmental studies. It has been demonstrated that they can be mapped by assimilating soil thermal and wetness information into surface energy balance models. The aim of this work is to determine whether enhancing the spatial resolution or temporal sampling frequency of soil moisture data could improve soil moisture or surface heat flux estimates. Two experiments are conducted in an area mainly covered by grassland, and land surface temperature (LST) observations from the Geostationary Operational Environmental Satellite (GOES) mission are assimilated together with either an enhanced L-band passive soil moisture product (9 km, 2–3 days) from the Soil Moisture Active Passive (SMAP) mission or a merged product (36 km, quasi-daily) from the SMAP and the Soil Moisture Ocean Salinity (SMOS) mission. The results suggest that the availability of soil moisture observations is increased by 41% after merging data from the SMAP and the SMOS missions. A comparison with results from a previous study that assimilated a coarser SMAP soil moisture product (36 km, 2–3 days) suggests that enhancing the temporal sampling frequency of soil moisture observations leads to improved soil moisture estimates at both the surface and root zone, and the largest improvement is seen in the bias metric (0.008 and 0.007 m3 m−3 on average at the surface and root zone, respectively). Enhancing the spatial resolution, however, does not significantly improve soil moisture estimates, particularly at the surface. Surface heat flux estimates from assimilating soil moisture data of different spatial or temporal resolutions are very similar.

scholarly journals Asymmetric Response of the Equatorial Pacific SST to Climate Warming and Cooling

2017 ◽  
Vol 30 (18) ◽  
pp. 7255-7270 ◽  
Author(s):  
Fukai Liu ◽  
Yiyong Luo ◽  
Jian Lu ◽  
Oluwayemi Garuba ◽  
Xiuquan Wan
Keyword(s):  
Heat Flux ◽  
Heat Budget ◽  
Dominant Role ◽  
Surface Heat ◽  
Equatorial Pacific ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Asymmetric Structure ◽  
Linear Component ◽  
Budget Analysis

Abstract The response of the equatorial Pacific Ocean to heat fluxes of equal amplitude but opposite sign is investigated using the Community Earth System Model (CESM). Results show a strong asymmetry in SST changes. In the eastern equatorial Pacific (EEP), the warming responding to the positive forcing exceeds the cooling response to the negative forcing, whereas in the western equatorial Pacific (WEP) it is the other way around and the cooling surpasses the warming. This leads to a zonal dipole asymmetric structure, with positive values in the east and negative values in the west. A surface heat budget analysis suggests that the SST asymmetry mainly results from the oceanic horizontal advection and vertical entrainment, with both of their linear and nonlinear components playing a role. For the linear component, its change appears to be more significant over the EEP (WEP) in the positive (negative) forcing scenario, favoring the seesaw pattern of the SST asymmetry. For the nonlinear component, its change acts to warm (cool) the EEP (WEP) in both scenarios, also favorable for the development of the SST asymmetry. Additional experiments with a slab ocean confirm the dominant role of ocean dynamical processes for this SST asymmetry. The net surface heat flux, in contrast, works to reduce the SST asymmetry through its shortwave radiation and latent heat flux components, with the former being related to the nonlinear relationship between SST and convection, and the latter being attributable to Newtonian damping and air–sea stability effects. The suppressing effect of shortwave radiation on SST asymmetry is further verified by partially coupled overriding experiments.

The Measurement of Surface Heat Flux Using the Peltier Effect

1989 ◽  
Vol 111 (3) ◽  
pp. 798-803 ◽  
Author(s):  
E. C. Shewen ◽  
K. G. T. Hollands ◽  
G. D. Raithby
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Physical Models ◽  
Peltier Effect ◽  
Absolute Accuracy ◽  
Measuring Surface ◽  
Wide Range

Calorimetric methods for measuring surface heat flux use Joulean heating to keep the surface isothermal. This limits them to measuring the heat flux of surfaces that are hotter than their surroundings. Presented in this paper is a method whereby reversible Peltier effect heat transfer is used to maintain this isothermality, making it suitable for surfaces that are either hotter or colder than the surroundings. The paper outlines the theory for the method and describes physical models that have been constructed, calibrated, and tested. The tested physical models were found capable of measuring heat fluxes with an absolute accuracy of 1 percent over a wide range of temperature (5–50°C) and heat flux (15–500 W/m2), while maintaining isothermality to within 0.03 K. A drawback of the method is that it appears to be suited only for measuring the heat flux from thick metallic plates.

Dynamic Calibration of a Coaxial Thermocouples for Short Duration Transient Measurements

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Rakesh Kumar ◽  
Niranjan Sahoo
Keyword(s):  
Heat Flux ◽  
Finite Element ◽  
Heat Conduction ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Dynamic Calibration ◽  
One Dimensional ◽  
Surface Heat Fluxes ◽  
Heat Loads

Coaxial thermocouple sensors are suitable for measuring highly transient surface heat fluxes because the response times of these sensors are very small (∼0.1 ms). These robust sensors have the flexibility of mounting them directly on the surface of any geometry. So, they have been routinely used in ground-based impulse facilities as temperature sensors where rapid changes in heat loads are expected on aerodynamic models. Subsequently, the surface heat fluxes are predicted from the transient temperatures by appropriate one-dimensional heat conduction modeling for semi-infinite body. In this backdrop, the purpose of this work is to design and fabricate K-type coaxial thermocouples in-house and calibrate them under similar nature of heat loads by using simple laboratory instruments. Here, two methods of dynamic calibration of coaxial thermocouples have been discussed, where the known step loads are applied through radiation and conduction modes of heat transfer. Using appropriate one dimensional heat conduction modeling, the surface heat fluxes are predicted from the measured temperature histories and subsequently compared with the input heat loads. The recovery of surface heat flux from laser based calibration experiment under-predicts by 4% from its true input heat load. Similarly, recovery of surface heat flux from the conduction mode calibration experiments under-predicts 6% from its true input value. Further, finite-element based numerical study is performed on the coaxial thermocouple model to obtain surface temperatures with same heat loads as used in the experiments. The recovery of surface temperatures from finite element simulation is achieved within an accuracy of ±0.3% from the experiment.

Measurements of Burnout Conditions for Flow of Boiling Water in a Vertical Annulus

1964 ◽  
Vol 86 (3) ◽  
pp. 393-404 ◽  
Author(s):  
K. M. Becker ◽  
G. Hernborg
Keyword(s):  
Heat Flux ◽  
Surface Heat Flux ◽  
Flow Model ◽  
Film Flow ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Nonuniform Heating ◽  
Steam Quality ◽  
Internal Heating ◽  
Inner Surface

The present paper deals with measurements of burnout conditions for flow of boiling water in an annulus with an inner diameter of 9.92 mm, an outer diameter of 17.42 mm, and a heated length of 608 mm. Data were obtained in respect of external heating only, internal heating only, and dual uniform and nonuniform heating. The following ranges of variables were studied and 978 burnout measurements were obtained. Pressure: 8.5 < p < 37.5 kg/cm2; Inlet subcooling: 60 < Δtsub < 205 deg C; Steam quality: 0.10 < x < 0.91; Inner surface heat flux: 0 < (q/A)i < 303 W/cm2; Outer surface heat flux: 0 < (q/A)0 < 374 W/cm2; Mass velocity: 71 < m˙/F < 961 kg/m2sec. The results are presented in diagrams where the burnout steam qualities, xBO, were plotted against the pressure with the surface heat fluxes as parameters. The data have been correlated by curves. The scatter of the data around the curves is less than ±5 percent. In the case of equal heat fluxes on both walls of the annulus, burnout always occurred on the inner wall, and the data compared rather well with round duct data. When the annulus was heated internally only, the data showed very low burnout values in comparison with the results for dual heating and round ducts. This disagreement was explained by considering the climbing film flow model and by the fact that only a fraction of the channel perimeter was heated. For external heating the data are somewhat lower than corresponding round duct data, but rather high in comparison with internal heating. The climbing film flow model was also used to interpret this observation. For dual nonuniform heating it was found that the outer surface may be overloaded from 30 to 70 percent compared with the inner surface without reducing the margin of safety in respect to burnout for the annulus. It was further observed that when the heat flux for the wall on which burnout occurs is increased, the burnout steam quality for the channel decreases. If, however, the heat flux for the opposite wall is increased, the burnout steam quality also increases. It was also observed that the highest burnout values are obtained when burnout occurs simultaneously on both cylinders. Finally, the results have been compared with annuli and rod cluster data in published works, and a method for predicting burnout conditions in rod clusters has been proposed.

scholarly journals Mixed Layer Heat Variations in the South China Sea Observed by Argo Float and Reanalysis Data during 2012–2015

2019 ◽  
Vol 11 (19) ◽  
pp. 5429 ◽  
Author(s):  
Liang ◽  
Xing ◽  
Wang ◽  
Zeng
Keyword(s):  
Heat Flux ◽  
South China Sea ◽  
Mixed Layer ◽  
South China ◽  
Surface Heat Flux ◽  
Heat Budget ◽  
Surface Heat ◽  
Horizontal Advection ◽  
Net Heat Flux ◽  
Mixed Layer Heat Budget

The atmospheric and oceanic causes of mixed layer heat variations in the South China Sea (SCS) are examined using data from six long-lived Array for Real-time Geostrophic Oceanography (Argo) floats. The mixed layer heat budget along each float trajectory is evaluated based on direct measurements, satellite and reanalysis datasets. Our results suggest that the mixed layer heat balance in the SCS has distinct spatial and seasonal variations. The amplitude of all terms in the mixed layer heat budget equation is significantly larger in the northern SCS than in the southern SCS, especially in winter. In the northern SCS, the mixed layer heat budget is controlled by the local surface heat flux and horizontal advection terms in winter, and the net heat flux term in summer. In the western and southeastern SCS, the mixed layer heat budget is dominated by the net surface heat flux in both winter and summer. Further analysis shows that in the SCS, surface shortwave radiation and geostrophic heat advection are major contributors to net heat flux and horizontal advection, respectively. Unlike the net heat flux and horizontal advection, the vertical entrainment is a sink term in general. The rate of mixed layer deepening is the most important factor in the entrainment rate, and a barrier layer may decrease the temperature difference between the bottom of the mixed layer and the water beneath. Residual analysis suggests that the residual term in the equation is due to the inexact calculation of heat geostrophic advection, other missing terms, and unresolved physical ocean dynamic processes.

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