The Annual Cycle of Heat Content in the Peru Current Region*

Abstract The relative importance of the processes responsible for the annual cycle in the upper-ocean heat content in the Peru Current, in the southeastern tropical Pacific, was diagnosed from an oceanic analysis dataset. It was found that the annual cycle of heat content is forced mainly by insolation. However, the ocean dynamical processes play an important role in producing different regional budget characteristics. In a band 500 km from the coast of Peru, the annual heat content changes in this region are relatively large and can be approximated as sea surface temperature (SST) changes in a fixed-depth mixed layer. The annual cycle of the albedo associated with low-level clouds enhances the annual cycle in insolation, which explains the relatively strong annual cycle of heat content. These clouds, to a large extent, act as a feedback to SST, but a small additional forcing, which is proposed to be cold air advection in this paper, is needed to explain the fact that the maximum cloudiness leads the lowest SST by around a month. Ocean dynamics is important closer to the coast, where upwelling acts partly as damping of the heat content changes and forces it to peak earlier than farther offshore. In a band farther to the southwest, locally wind-forced thermocline motions, which become shallower (deeper) in the warm (cool) season, partially cancel the effect of net surface heat fluxes, whose annual cycle is comparable to that in the region previously mentioned, producing a relatively small annual cycle of heat content. The local forcing appears to be associated with the annual meridional displacements of the South Pacific anticyclone. The annual cycle in SST is also relatively small, which is probably due to the changes in the temperature of the water entrained into the mixed layer associated with the thermocline motions, but also to a mixed layer deeper than that closer to the coast.

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Seasonal mixed layer heat budget in coastal waters off Angola

10.5194/egusphere-egu21-6122 ◽

2021 ◽

Author(s):

Mareike Körner ◽

Peter Brandt ◽

Marcus Dengler

Keyword(s):

Mixed Layer ◽

Heat Budget ◽

Heat Content ◽

Nutrient Supply ◽

Surface Heat ◽

Heat Fluxes ◽

Driving Mechanism ◽

Near Surface ◽

Surface Heat Fluxes ◽

Mixed Layer Heat Budget

<p>The Angolan shelf system represents a highly productive ecosystem that exhibits pronounced seasonal variability. Productivity peaks in austral winter when seasonally prevailing upwelling favorable winds are weakest. Thus, other processes than local wind-driven upwelling contribute to the near-coastal cooling and nutrient supply during this season. Possible processes that lead to changes of the mixed-layer heat content does not only include local mechanism but also the passage of remotely forced coastally trapped waves. Understanding the driving mechanism of changes in the mixed-layer heat content that may be locally or remotely forced are vital for understanding of upward nutrient supply and biological productivity off Angola. Here, we investigate the seasonal mixed layer heat budget by analyzing atmospheric and oceanic causes for heat content variability. We calculate monthly estimates of surface heat fluxes, horizontal advection from near-surface velocities, horizontal eddy advection, and vertical entrainment. Additionally, diapycnal heat fluxes at the mixed-layer base are determined from shipboard and glider microstructure data. The results are discussed in reference to the variability of the eastern boundary circulation, surface heat fluxes and wind forcing.</p>

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On the Hyperbolicity of the Bulk Air–Sea Heat Flux Functions: Insights into the Efficiency of Air–Sea Moisture Disequilibrium for Tropical Cyclone Intensification

Monthly Weather Review ◽

10.1175/mwr-d-20-0324.1 ◽

2021 ◽

Vol 149 (5) ◽

pp. 1517-1534

Author(s):

Benjamin Jaimes de la Cruz ◽

Lynn K. Shay ◽

Joshua B. Wadler ◽

Johna E. Rudzin

Keyword(s):

Tropical Cyclone ◽

Surface Wind ◽

Heat Content ◽

Surface Heat ◽

Heat Fluxes ◽

Ocean Heat Uptake ◽

Surface Heat Fluxes ◽

Heat Uptake ◽

Moisture Fluxes ◽

New Perspective

AbstractSea-to-air heat fluxes are the energy source for tropical cyclone (TC) development and maintenance. In the bulk aerodynamic formulas, these fluxes are a function of surface wind speed U10 and air–sea temperature and moisture disequilibrium (ΔT and Δq, respectively). Although many studies have explained TC intensification through the mutual dependence between increasing U10 and increasing sea-to-air heat fluxes, recent studies have found that TC intensification can occur through deep convective vortex structures that obtain their local buoyancy from sea-to-air moisture fluxes, even under conditions of relatively low wind. Herein, a new perspective on the bulk aerodynamic formulas is introduced to evaluate the relative contribution of wind-driven (U10) and thermodynamically driven (ΔT and Δq) ocean heat uptake. Previously unnoticed salient properties of these formulas, reported here, are as follows: 1) these functions are hyperbolic and 2) increasing Δq is an efficient mechanism for enhancing the fluxes. This new perspective was used to investigate surface heat fluxes in six TCs during phases of steady-state intensity (SS), slow intensification (SI), and rapid intensification (RI). A capping of wind-driven heat uptake was found during periods of SS, SI, and RI. Compensation by larger values of Δq > 5 g kg−1 at moderate values of U10 led to intense inner-core moisture fluxes of greater than 600 W m−2 during RI. Peak values in Δq preferentially occurred over oceanic regimes with higher sea surface temperature (SST) and upper-ocean heat content. Thus, increasing SST and Δq is a very effective way to increase surface heat fluxes—this can easily be achieved as a TC moves over deeper warm oceanic regimes.

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On the Accuracy of the Simple Ocean Data Assimilation Analysis for Estimating Heat Budgets of the Near-Surface Arabian Sea and Bay of Bengal*

Journal of Physical Oceanography ◽

10.1175/jpo-2678.1 ◽

2005 ◽

Vol 35 (3) ◽

pp. 395-400 ◽

Cited By ~ 10

Author(s):

S S C. Shenoi ◽

D. Shankar ◽

S. R. Shetye

Keyword(s):

Data Assimilation ◽

Bay Of Bengal ◽

Arabian Sea ◽

Heat Budget ◽

Heat Content ◽

Heat Fluxes ◽

Simple Ocean Data Assimilation ◽

Near Surface ◽

Surface Heat Fluxes ◽

Ocean Data Assimilation

Abstract The accuracy of data from the Simple Ocean Data Assimilation (SODA) model for estimating the heat budget of the upper ocean is tested in the Arabian Sea and the Bay of Bengal. SODA is able to reproduce the changes in heat content when they are forced more by the winds, as in wind-forced mixing, upwelling, and advection, but not when they are forced exclusively by surface heat fluxes, as in the warming before the summer monsoon.

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Spring Mixing: Turbulence and Internal Waves during Restratification on the New England Shelf

Journal of Physical Oceanography ◽

10.1175/jpo2821.1 ◽

2005 ◽

Vol 35 (12) ◽

pp. 2425-2443 ◽

Cited By ~ 55

Author(s):

J. A. MacKinnon ◽

M. C. Gregg

Keyword(s):

New England ◽

Internal Waves ◽

Mixed Layer ◽

Wave Interaction ◽

Heat Fluxes ◽

Surface Mixed Layer ◽

Turbulent Dissipation ◽

Surface Heat Fluxes ◽

Bottom Boundary Layers ◽

Diapycnal Diffusivity

Abstract Integrated observations are presented of water property evolution and turbulent microstructure during the spring restratification period of April and May 1997 on the New England continental shelf. Turbulence is shown to be related to surface mixed layer entrainment and shear from low-mode near-inertial internal waves. The largest turbulent diapycnal diffusivity and associated buoyancy fluxes were found at the bottom of an actively entraining and highly variable wind-driven surface mixed layer. Away from surface and bottom boundary layers, turbulence was systematically correlated with internal wave shear, though the nature of that relationship underwent a regime shift as the stratification strengthened. During the first week, while stratification was weak, the largest turbulent dissipation away from boundaries was coincident with shear from mode-1 near-inertial waves generated by passing storms. Wave-induced Richardson numbers well below 0.25 and density overturning scales of several meters were observed. Turbulent dissipation rates in the region of peak shear were consistent in magnitude with several dimensional scalings. The associated average diapycnal diffusivity exceeded 10−3 m2 s−1. As stratification tripled, Richardson numbers from low-mode internal waves were no longer critical, though turbulence was still consistently elevated in patches of wave shear. Kinematically, dissipation during this period was consistent with the turbulence parameterization proposed by MacKinnon and Gregg, based on a reinterpretation of wave–wave interaction theory. The observed growth of temperature gradients was, in turn, consistent with a simple one-dimensional model that vertically distributed surface heat fluxes commensurate with calculated turbulent diffusivities.

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Diagnosing Natural Variability of North Atlantic Water Masses in HadCM3

Journal of Climate ◽

10.1175/jcli3348.1 ◽

2005 ◽

Vol 18 (12) ◽

pp. 1925-1941 ◽

Cited By ~ 7

Author(s):

Keith Haines ◽

Chris Old

Keyword(s):

Mixed Layer ◽

General Circulation ◽

Circulation Model ◽

Surface Heat ◽

Surface Fluxes ◽

Heat Fluxes ◽

Mode Water ◽

Surface Heat Fluxes ◽

Mode Waters ◽

Winter Mixed Layer

Abstract A study of thermally driven water mass transformations over 100 yr in the ocean component of the Third Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3) is presented. The processes of surface-forced transformations, subduction and mixing, both above and below the winter mixed layer base, are quantified. Subtropical Mode Waters are formed by surface heat fluxes and subducted at more or less the same rate. However, Labrador Seawater and Nordic Seawater classes (the other main subduction classes) are primarily formed by mixing within the mixed layer with very little formation directly from surface heat fluxes. The Subpolar Mode Water classes are dominated by net obduction of water back into the mixed layer from below. Subtropical Mode Water (18°C) variability shows a cycle of formation by surface fluxes, subduction ∼2 yr later, followed by mixing with warmer waters below the winter mixed layer base during the next 3 yr, and finally obduction back into the mixed layer at 21°C, ∼5 yr after the original formation. Surface transformation of Subpolar Mode Waters, ∼12°C, are led by surface transformations of warmer waters by up to 5 yr as water is transferred from the subtropical gyre. They are also led by obduction variability from below the mixed layer, by ∼2 yr. The variability of obduction in Subpolar Mode Waters also appears to be preceded, by 3–5 yr, by variability in subduction of Labrador Sea Waters at ∼6°C. This supports a mechanism in which southward-propagating Labrador seawater anomalies below the subpolar gyre can influence the upper water circulation and obduction into the mixed layer.

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Long-term global ocean heat content change driven by sub-polar surface heat fluxes

10.1002/essoar.10504695.1 ◽

2020 ◽

Author(s):

Taimoor Sohail ◽

Damien B Irving ◽

Jan David Zika ◽

Ryan M Holmes ◽

John Alexander Church

Keyword(s):

Heat Content ◽

Surface Heat ◽

Heat Fluxes ◽

Ocean Heat Content ◽

Global Ocean ◽

Polar Surface ◽

Surface Heat Fluxes ◽

Content Change

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Seasonal Cycle of the Mixed Layer Heat Budget in the Northeastern Tropical Atlantic Ocean

Journal of Climate ◽

10.1175/jcli-d-13-00037.1 ◽

2013 ◽

Vol 26 (20) ◽

pp. 8169-8188 ◽

Cited By ~ 19

Author(s):

Gregory R. Foltz ◽

Claudia Schmid ◽

Rick Lumpkin

Keyword(s):

Mixed Layer ◽

Annual Cycle ◽

Turbulent Mixing ◽

Seasonal Cycle ◽

Heat Budget ◽

Heat Content ◽

Boreal Summer ◽

Tropical Atlantic ◽

Mixed Layer Heat Budget ◽

Vertical Turbulent Mixing

Abstract The seasonal cycle of the mixed layer heat budget in the northeastern tropical Atlantic (0°–25°N, 18°–28°W) is quantified using in situ and satellite measurements together with atmospheric reanalysis products. This region is characterized by pronounced latitudinal movements of the intertropical convergence zone (ITCZ) and strong meridional variations of the terms in the heat budget. Three distinct regimes within the northeastern tropical Atlantic are identified. The trade wind region (15°–25°N) experiences a strong annual cycle of mixed layer heat content that is driven by approximately out-of-phase annual cycles of surface shortwave radiation (SWR), which peaks in boreal summer, and evaporative cooling, which reaches a minimum in boreal summer. The surface heat-flux-induced changes in the mixed layer heat content are damped by a strong annual cycle of cooling from vertical turbulent mixing, estimated from the residual in the heat balance. In the ITCZ core region (3°–8°N) a weak seasonal cycle of mixed layer heat content is driven by a semiannual cycle of SWR and damped by evaporative cooling and vertical turbulent mixing. On the equator the seasonal cycle of mixed layer heat content is balanced by an annual cycle of SWR that reaches a maximum in October and a semiannual cycle of turbulent mixing that cools the mixed layer most strongly during May–July and November. These results emphasize the importance of the surface heat flux and vertical turbulent mixing for the seasonal cycle of mixed layer heat content in the northeastern tropical Atlantic.

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The Value of Sustained Ocean Observations for Sea Ice Predictions in the Barents Sea

Journal of Climate ◽

10.1175/jcli-d-19-0179.1 ◽

2019 ◽

Vol 32 (20) ◽

pp. 7017-7035 ◽

Cited By ~ 1

Author(s):

Mitchell Bushuk ◽

Xiaosong Yang ◽

Michael Winton ◽

Rym Msadek ◽

Matthew Harrison ◽

...

Keyword(s):

Sea Ice ◽

Barents Sea ◽

Initial Conditions ◽

Heat Budget ◽

Heat Content ◽

Arctic Sea Ice ◽

Heat Fluxes ◽

Seasonal Forecasts ◽

Surface Heat Fluxes ◽

The Barents Sea

ABSTRACT Dynamical prediction systems have shown potential to meet the emerging need for seasonal forecasts of regional Arctic sea ice. Observationally constrained initial conditions are a key source of skill for these predictions, but the direct influence of different observation types on prediction skill has not yet been systematically investigated. In this work, we perform a hierarchy of observing system experiments with a coupled global data assimilation and prediction system to assess the value of different classes of oceanic and atmospheric observations for seasonal sea ice predictions in the Barents Sea. We find notable skill improvements due to the inclusion of both sea surface temperature (SST) satellite observations and subsurface conductivity–temperature–depth (CTD) measurements. The SST data are found to provide the crucial source of interannual variability, whereas the CTD data primarily provide climatological and trend improvements. Analysis of the Barents Sea ocean heat budget suggests that ocean heat content anomalies in this region are driven by surface heat fluxes on seasonal time scales.

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Development of the temperature and salinity structure of the upper ocean over two months in an area 150x150 km

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1983.0006 ◽

1983 ◽

Vol 308 (1503) ◽

pp. 311-325 ◽

Cited By ~ 4

Keyword(s):

Heat Budget ◽

Salt Content ◽

Heat Content ◽

Time History ◽

Heat Fluxes ◽

Spatial Average ◽

Survey Area ◽

Surface Heat Fluxes ◽

History Of ◽

Salinity Structure

During the two months of the JASIN experiment a regular conductivity-temperaturedepth station pattern was worked by Hr. Neth. Ms. Tydeman , giving a total of eight surveys of temperature and salinity structure in an area 100 km x 150 km. The data are averaged to obtain hourly and spatial mean profiles. It is shown that this averaging conserves heat and salt content. The spatial mean profiles are compared with heat budget computations, and it is found that, on average, surface heat fluxes dominate the time history of the oceanic heat content on the scale of the whole survey area. On smaller scales advection due to mesoscale structures dominates, masking any differences in heating in different water masses. Comparison with results from a onedimensional mixed-layer model indicates that this type of model satisfactorily simulates the development of the temperature profile as a spatial average for the survey area.

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