Simulated changes of the Southern Ocean air-sea heat flux feedback in a warmer climate

2020 ◽  
Author(s):  
Liping Zhang ◽  
William Cooke
Keyword(s):  
Heat Flux ◽  
Southern Ocean ◽  
Heat Flux Feedback

scholarly journals Estimates of Air–Sea Feedbacks on Sea Surface Temperature Anomalies in the Southern Ocean

2016 ◽  
Vol 29 (2) ◽  
pp. 439-454 ◽  
Author(s):  
Ute Hausmann ◽  
Arnaud Czaja ◽  
John Marshall
Keyword(s):  
Heat Flux ◽  
Southern Ocean ◽  
Surface Temperature ◽  
Radiative Heat ◽  
Spatial Scales ◽  
Heat Fluxes ◽  
Sea Surface ◽  
Turbulent Heat ◽  
Damping Effect ◽  
Heat Flux Feedback

Abstract Sea surface temperature (SST) air–sea feedback strengths and associated decay time scales in the Southern Ocean (SO) are estimated from observations and reanalysis datasets of SST, air–sea heat fluxes, and ocean mixed layer depths. The spatial, seasonal, and scale dependence of the air–sea heat flux feedbacks is mapped in circumpolar bands and implications for SST persistence times are explored. It is found that the damping effect of turbulent heat fluxes dominates over that due to radiative heat fluxes. The turbulent heat flux feedback acts to damp SSTs in all bands and spatial scales and in all seasons, at rates varying between 5 and 25 W m−2 K−1, while the radiative heat flux feedback has a more uniform spatial distribution with a magnitude rarely exceeding 5 W m−2 K−1. In particular, the implied net air–sea feedback (turbulent + radiative) on SST south of the polar front, and in the region of seasonal sea ice, is as weak as 5–10 W m−2 K−1 in the summertime on large spatial scales. Air–sea interaction alone thus allows SST signals induced around Antarctica in the summertime to persist for several seasons. The damping effect of mixed layer entrainment on SST anomalies averages to approximately 20 W m−2 K−1 across the ACC bands in the summer-to-winter entraining season and thereby reduces summertime SST persistence to less than half of that predicted by air–sea interaction alone (i.e., 3–6 months).

scholarly journals Mechanisms controlling the SST air-sea heat flux feedback and its dependence on spatial scale

2016 ◽  
Vol 48 (3-4) ◽  
pp. 1297-1307 ◽  
Author(s):  
Ute Hausmann ◽  
Arnaud Czaja ◽  
John Marshall
Keyword(s):  
Heat Flux ◽  
Spatial Scale ◽  
Heat Flux Feedback

scholarly journals Annual Southern Ocean heat flux measured for first time

Eos ◽  
2012 ◽  
Vol 93 (44) ◽  
pp. 452-452
Author(s):  
Colin Schultz
Keyword(s):  
Heat Flux ◽  
Southern Ocean ◽  
First Time

scholarly journals Assessing Surface Heat Flux Products with In Situ Observations over the Australian Sector of the Southern Ocean

2019 ◽  
Vol 36 (9) ◽  
pp. 1849-1861
Author(s):  
Vidhi Bharti ◽  
Eric Schulz ◽  
Christopher W. Fairall ◽  
Byron W. Blomquist ◽  
Yi Huang ◽  
...  
Keyword(s):  
Heat Flux ◽  
Southern Ocean ◽  
Sensible Heat Flux ◽  
Surface Heat ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Atmospheric Composition ◽  
Systematic Bias ◽  
Positive Bias

Given the large uncertainties in surface heat fluxes over the Southern Ocean, an assessment of fluxes obtained by European Centre for Medium-Range Weather Forecasts interim reanalysis (ERA-Interim) product, the Australian Integrated Marine Observing System (IMOS) routine observations, and the Objectively Analyzed Air–Sea Heat Fluxes (OAFlux) project hybrid dataset is performed. The surface fluxes are calculated using the COARE 3.5 bulk algorithm with in situ data obtained from the NOAA Physical Sciences Division flux system during the Clouds, Aerosols, Precipitation, Radiation, and Atmospheric Composition over the Southern Ocean (CAPRICORN) experiment on board the R/V Investigator during a voyage (March–April 2016) in the Australian sector of the Southern Ocean (43°–53°S). ERA-Interim and OAFlux data are further compared with the Southern Ocean Flux Station (SOFS) air–sea flux moored surface float deployed for a year (March 2015–April 2016) at ~46.7°S, 142°E. The results indicate that ERA-Interim (3 hourly at 0.25°) and OAFlux (daily at 1°) estimate sensible heat flux H s accurately to within ±5 W m−2 and latent heat flux H l to within ±10 W m−2. ERA-Interim gives a positive bias in H s at low latitudes (<47°S) and in H l at high latitudes (>47°S), and OAFlux displays consistently positive bias in H l at all latitudes. No systematic bias with respect to wind or rain conditions was observed. Although some differences in the bulk flux algorithms are noted, these biases can be largely attributed to the uncertainties in the observations used to derive the flux products.

scholarly journals Observational Assessment of Nonlocal Heat Flux Feedback in the North Atlantic by GEFA

2013 ◽  
Vol 52 (3) ◽  
pp. 645-653 ◽  
Author(s):  
Na Wen ◽  
Zhengyu Liu ◽  
Qinyu Liu
Keyword(s):  
Heat Flux ◽  
North Atlantic ◽  
Surface Wind ◽  
Turbulent Heat ◽  
Observational Assessment ◽  
The North ◽  
The North Atlantic ◽  
Flux Response ◽  
Sst Anomalies ◽  
Heat Flux Feedback

AbstractMost previous studies have proven the local negative heat flux feedback (the surface heat flux response to SST anomalies) in the midlatitude areas. However, it is uncertain whether a nonlocal heat flux feedback can be observed. In this paper, the generalized equilibrium feedback assessment (GEFA) method is employed to examine the full surface turbulent heat flux response to SST in the North Atlantic Ocean using NCEP–NCAR reanalysis data. The results not only confirm the dominant local negative feedback, but also indicate a robust nonlocal positive feedback of the Gulf Stream Extension (GSE) SST to the downstream heat flux in the subpolar region. This nonlocal feedback presents a strong seasonality, with response magnitudes of in winter and in summer. Further study indicates that the nonlocal effect is initiated by the adjustments of the downstream surface wind to the GSE SST anomalies.

A Comparison of Southern Ocean Air–Sea Buoyancy Flux from an Ocean State Estimate with Five Other Products

2011 ◽  
Vol 24 (24) ◽  
pp. 6283-6306 ◽  
Author(s):  
Ivana Cerovečki ◽  
Lynne D. Talley ◽  
Matthew R. Mazloff
Keyword(s):  
Heat Flux ◽  
Southern Ocean ◽  
Heat Loss ◽  
Large Scale ◽  
Heat Fluxes ◽  
Buoyancy Flux ◽  
Western Boundary ◽  
Turbulent Heat ◽  
Radiative Fluxes ◽  
State Estimate

Abstract The authors have intercompared the following six surface buoyancy flux estimates, averaged over the years 2005–07: two reanalyses [the recent ECMWF reanalysis (ERA-Interim; hereafter ERA), and the National Centers for Environmental Prediction (NCEP)–NCAR reanalysis 1 (hereafter NCEP1)], two recent flux products developed as an improvement of NCEP1 [the flux product by Large and Yeager and the Southern Ocean State Estimate (SOSE)], and two ad hoc air–sea flux estimates that are obtained by combining the NCEP1 or ERA net radiative fluxes with turbulent flux estimates using the Coupled Ocean–Atmosphere Response Experiment (COARE) 3.0 bulk formulas with NCEP1 or ERA input variables. The accuracy of SOSE adjustments of NCEP1 atmospheric fields (which SOSE uses as an initial guess and a constraint) was assessed by verification that SOSE reduces the biases in the NCEP1 fluxes as diagnosed by the Working Group on Air–Sea Fluxes (Taylor), suggesting that oceanic observations may be a valuable constraint to improve atmospheric variables. Compared with NCEP1, both SOSE and Large and Yeager increase the net ocean heat loss in high latitudes, decrease ocean heat loss in the subtropical Indian Ocean, decrease net evaporation in the subtropics, and decrease net precipitation in polar latitudes. The large-scale pattern of SOSE and Large and Yeager turbulent heat flux adjustment is similar, but the magnitude of SOSE adjustments is significantly larger. Their radiative heat flux adjustments patterns differ. Turbulent heat fluxes determined by combining COARE bulk formulas with NCEP1 or ERA should not be combined with unmodified NCEP1 or ERA radiative fluxes as the net ocean heat gain poleward of 25°S becomes unrealistically large. The other surface flux products (i.e., NCEP1, ERA, Large and Yeager, and SOSE) balance more closely. Overall, the statistical estimates of the differences between the various air–sea heat flux products tend to be largest in regions with strong ocean mesoscale activity such as the Antarctic Circumpolar Current and the western boundary currents.

scholarly journals Time-Mean Flow as the Prevailing Contribution to the Poleward Heat Flux across the Southern Flank of the Antarctic Circumpolar Current: A Case Study in the Fawn Trough, Kerguelen Plateau

2013 ◽  
Vol 43 (3) ◽  
pp. 583-601 ◽  
Author(s):  
H. Sekma ◽  
Y.-H. Park ◽  
F. Vivier
Keyword(s):  
Heat Flux ◽  
Southern Ocean ◽  
Antarctic Circumpolar Current ◽  
Mean Flow ◽  
Kerguelen Plateau ◽  
The Mean ◽  
The Cross ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Southern Flank

Abstract The major mechanisms of the oceanic poleward heat flux in the Southern Ocean are still in debate. The long-standing belief stipulates that the poleward heat flux across the Antarctic Circumpolar Current (ACC) is mainly due to mesoscale transient eddies and the cross-stream heat flux by time-mean flow is insignificant. This belief has recently been challenged by several numerical modeling studies, which stress the importance of mean flow for the meridional heat flux in the Southern Ocean. Here, this study analyzes moored current meter data obtained recently in the Fawn Trough, Kerguelen Plateau, to estimate the cross-stream heat flux caused by the time-mean flow and transient eddies. It is shown that the poleward eddy heat flux in this southern part of the ACC is negligible, while that from the mean flow is overwhelming by two orders of magnitude. This is due to the unusual anticlockwise turning of currents with decreasing depth, which is associated with significant bottom upwelling engendered by strong bottom currents flowing over the sloping topography of the trough. The circumpolar implications of these local observations are discussed in terms of the depth-integrated linear vorticity budget, which suggests that the six topographic features along the southern flank of the ACC equivalent to the Fawn Trough case would yield sufficient poleward heat flux to balance the oceanic heat loss in the subpolar region. As eddy activity on the southern flank of the ACC is too weak to transport sufficient heat poleward, the nonequivalent barotropic structure of the mean flow in several topographically constricted passages should accomplish the required task.

Estimation of the Surface Heat Flux Response to Sea Surface Temperature Anomalies over the Global Oceans

2005 ◽  
Vol 18 (21) ◽  
pp. 4582-4599 ◽  
Author(s):  
Sungsu Park ◽  
Clara Deser ◽  
Michael A. Alexander
Keyword(s):  
Heat Flux ◽  
North Atlantic ◽  
Surface Heat Flux ◽  
Surface Wind ◽  
Surface Heat ◽  
Radiative Flux ◽  
Turbulent Heat ◽  
Global Oceans ◽  
Sst Anomalies ◽  
Heat Flux Feedback

Abstract The surface heat flux response to underlying sea surface temperature (SST) anomalies (the surface heat flux feedback) is estimated using 42 yr (1956–97) of ship-derived monthly turbulent heat fluxes and 17 yr (1984–2000) of satellite-derived monthly radiative fluxes over the global oceans for individual seasons. Net surface heat flux feedback is generally negative (i.e., a damping of the underlying SST anomalies) over the global oceans, although there is considerable geographical and seasonal variation. Over the North Pacific Ocean, net surface heat flux feedback is dominated by the turbulent flux component, with maximum values (28 W m−2 K−1) in December–February and minimum values (5 W m−2 K−1) in May–July. These seasonal variations are due to changes in the strength of the climatological mean surface wind speed and the degree to which the near-surface air temperature and humidity adjust to the underlying SST anomalies. Similar features are observed over the extratropical North Atlantic Ocean with maximum (minimum) feedback values of approximately 33 W m−2 K−1 (9 W m−2 K−1) in December–February (June–August). Although the net surface heat flux feedback may be negative, individual components of the feedback can be positive depending on season and location. For example, over the midlatitude North Pacific Ocean during late spring to midsummer, the radiative flux feedback associated with marine boundary layer clouds and fog is positive, and results in a significant enhancement of the month-to-month persistence of SST anomalies, nearly doubling the SST anomaly decay time from 2.8 to 5.3 months in May–July. Several regions are identified with net positive heat flux feedback: the tropical western North Atlantic Ocean during boreal winter, the Namibian stratocumulus deck off West Africa during boreal fall, and the Indian Ocean during boreal summer and fall. These positive feedbacks are mainly associated with the following atmospheric responses to positive SST anomalies: 1) reduced surface wind speed (positive turbulent heat flux feedback) over the tropical western North Atlantic and Indian Oceans, 2) reduced marine boundary layer stratocumulus cloud fraction (positive shortwave radiative flux feedback) over the Namibian stratocumulus deck, and 3) enhanced atmospheric water vapor (positive longwave radiative flux feedback) in the vicinity of the tropical deep convection region over the Indian Ocean that exceeds the negative shortwave radiative flux feedback associated with enhanced cloudiness.

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