Widespread Intense Turbulent Mixing in the Southern Ocean

Science ◽  
2004 ◽  
Vol 303 (5655) ◽  
pp. 210-213 ◽  
Author(s):  
A. C. N. Garabato
Keyword(s):  
Southern Ocean ◽  
Turbulent Mixing

scholarly journals Meridional and vertical variations of the water vapour isotopic composition in the marine boundary layer over the Atlantic and Southern Ocean

2020 ◽  
Vol 20 (9) ◽  
pp. 5811-5835 ◽  
Author(s):  
Iris Thurnherr ◽  
Anna Kozachek ◽  
Pascal Graf ◽  
Yongbiao Weng ◽  
Dimitri Bolshiyanov ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Time Series ◽  
Wind Speed ◽  
Southern Ocean ◽  
Water Vapour ◽  
Turbulent Mixing ◽  
Large Scale ◽  
Marine Boundary Layer ◽  
Sea Spray ◽  
Moisture Source

Abstract. Stable water isotopologues (SWIs) are useful tracers of moist diabatic processes in the atmospheric water cycle. They provide a framework to analyse moist processes on a range of timescales from large-scale moisture transport to cloud formation, precipitation and small-scale turbulent mixing. Laser spectrometric measurements on research vessels produce high-resolution time series of the variability of the water vapour isotopic composition in the marine boundary layer. In this study, we present a 5-month continuous time series of such ship-based measurements of δ2H and δ18O from the Antarctic Circumnavigation Expedition (ACE) in the Atlantic and the Southern Ocean in the time period from November 2016 to April 2017. We analyse the drivers of meridional SWI variations in the marine boundary layer across diverse climate zones in the Atlantic and Southern Ocean using Lagrangian moisture source diagnostics and relate vertical SWI differences to near-surface wind speed and ocean surface state. The median values of δ18O, δ2H and deuterium excess during ACE decrease continuously from low to high latitudes. These meridional SWI distributions reflect climatic conditions at the measurement and moisture source locations, such as air temperature, specific humidity and relative humidity with respect to sea surface temperature. The SWI variability at a given latitude is highest in the extratropics and polar regions with decreasing values equatorwards. This meridional distribution of SWI variability is explained by the variability in moisture source locations and its associated environmental conditions as well as transport processes. The westward-located moisture sources of water vapour in the extratropics are highly variable in extent and latitude due to the frequent passage of cyclones and thus widen the range of encountered SWI values in the marine boundary layer. Moisture loss during transport further contributes to the high SWI variability in the extratropics. In the subtropics and tropics, persistent anticyclones lead to well-confined narrow easterly moisture source regions, which is reflected in the weak SWI variability in these regions. Thus, the expected range of SWI signals at a given latitude strongly depends on the large-scale circulation. Furthermore, the ACE SWI time series recorded at 8.0 and 13.5 m above the ocean surface provide estimates of vertical SWI gradients in the lowermost marine boundary layer. On average, the vertical gradients with height found during ACE are -0.1‰m-1 for δ18O, -0.5‰m-1 for δ2H and 0.3 ‰ m−1 for deuterium excess. Careful calibration and post-processing of the SWI data and a detailed uncertainty analysis provide a solid basis for the presented gradients. Using sea spray concentrations and sea state conditions, we show that the vertical SWI gradients are particularly large during high wind speed conditions with increased contribution of sea spray evaporation or during low wind speed conditions due to weak vertical turbulent mixing. Although further SWI measurements at a higher vertical resolution are required to validate these findings, the simultaneous SWI measurements at several heights during ACE show the potential of SWIs as tracers for vertical mixing and sea spray evaporation in the lowermost marine boundary layer.

scholarly journals Correlations between Interannual SST Oscillations and Modeled Swell Impacts on Turbulent Mixing*

2015 ◽  
Vol 29 (1) ◽  
pp. 293-311 ◽  
Author(s):  
Yalin Fan ◽  
W. Erick Rogers ◽  
Tommy G. Jensen
Keyword(s):  
Indian Ocean ◽  
Southern Ocean ◽  
Turbulent Mixing ◽  
Southern Oscillation ◽  
Wind Waves ◽  
Sea Surface ◽  
Interannual Variations ◽  
The Indian Ocean ◽  
Wave Models ◽  
Sst Anomalies

Abstract The possibility of teleconnections between Southern Ocean swells and sea surface temperature (SST) anomalies on interannual time scales in the eastern Pacific Niño-3 region and southeastern Indian Ocean is investigated using numerical wave models. Two alternative parameterizations for swell dissipation are used. It is found that swell dissipation in the models is not directly correlated with large interannual variations such as El Niño–Southern Oscillation (ENSO) or the Indian Ocean dipole (IOD). However, using one of the two swell dissipation parameterizations, a correlation is found between observed SST anomalies and the modification of turbulent kinetic energy flux (TKEF) by Southern Ocean swells due to the damping of short wind waves: modeled reduction of TKEF is opposite in phase to the SST anomalies in the Niño-3 region, indicating a potential positive feedback. The modeled bimonthly averaged TKEF reduction in the southeastern Indian Ocean is also well correlated with the IOD mode.

scholarly journals Meridional and vertical variations of the water vapour isotopic composition in the marine boundary layer over the Atlantic and Southern Ocean

2019 ◽  
Author(s):  
Iris Thurnherr ◽  
Anna Kozachek ◽  
Pascal Graf ◽  
Yongbiao Weng ◽  
Dimitri Bolshiyanov ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Time Series ◽  
Wind Speed ◽  
Southern Ocean ◽  
Water Vapour ◽  
Turbulent Mixing ◽  
Large Scale ◽  
Marine Boundary Layer ◽  
Sea Spray ◽  
Moisture Source

Abstract. Stable water isotopologues (SWIs) are useful tracers of moist diabatic processes in the atmospheric water cycle. They provide a framework to analyse moist processes on a range of time scales from large-scale moisture transport to cloud formation, precipitation, and small-scale turbulent mixing. Laser spectrometric measurements on research vessels produce high-resolution time series of the variability of the water vapour isotopic composition in the marine boundary layer. In this study, we present a five-month continuous time series of such ship-based measurements of δ2H and δ18O from the Antarctic Circumnavigation Expedition (ACE) in the Atlantic and the Southern Ocean in the time period from November 2016 to April 2017. We analyse the drivers of meridional SWI variations in the marine boundary layer across diverse climate zones in the Atlantic and Southern Ocean using Lagrangian moisture source diagnostics and relate vertical SWI differences to near-surface wind speed and ocean surface state. The median values of δ18O, δ2H and d-excess during ACE decrease continuously from low to high latitudes. These meridional SWI distributions reflect climatic conditions at the measurement and moisture source sites, such as air temperature, specific humidity, and relative humidity with respect to sea surface temperature. The SWI variability at a given latitude is highest in the extratropics and polar regions with decreasing values equatorwards. This meridional distribution of SWI variability is explained by the variability in moisture source locations and its associated environmental conditions as well as transport processes. The westward located moisture sources of water vapour in the extratropics are highly variable in extent and latitude due to the frequent passage of cyclones and thus widen the range of encountered SWI values in the marine boundary layer. Moisture loss during transport further contributes to the high SWI variability in the extratropics. In the subtropics and tropics, persistent anticyclones lead to well-confined narrow easterly moisture source regions, which is reflected in the low SWI variability in these regions. Thus, the expected range of SWI signals at a given latitude strongly depends on the large-scale circulation. Furthermore, the ACE SWI time series recorded at different heights above the ocean surface provide estimates of vertical SWI gradients in the lowermost marine boundary layer. On average, the vertical gradients with height found during ACE are −0.1 ‰ m−1 for δ18O, −0.5 ‰ m−1 for δ2H and 0.3 ‰ m−1 for d-excess. Careful calibration and post-processing of the SWI data and a detailed uncertainty analysis provide a solid basis for the presented gradients. Using sea spray concentrations and sea state conditions, we show that the vertical SWI gradients are particularly large during high wind speed conditions with increased contribution of sea spray evaporation or during low wind speed conditions due to weak vertical turbulent mixing and dominating effects from non-equilibrium fractionation. Although further SWI measurements at a higher vertical resolution are required to validate these findings, the simultaneous SWI measurements at several heights during ACE show the potential of SWIs as tracers for vertical mixing and sea spray evaporation in the lowermost marine boundary layer.

scholarly journals Topographic enhancement of vertical turbulent mixing in the Southern Ocean

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
A. Mashayek ◽  
R. Ferrari ◽  
S. Merrifield ◽  
J. R. Ledwell ◽  
L. St Laurent ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Turbulent Mixing ◽  
Vertical Turbulent Mixing

The impact of lee waves on the Southern Ocean circulation

2021 ◽  
Author(s):  
Luwei Yang ◽  
Maxim Nikurashin ◽  
Andrew McC. Hogg ◽  
Bernadette M. Sloyan
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
Turbulent Mixing ◽  
Wave Drag ◽  
Global Ocean ◽  
Mixing Effects ◽  
Lee Waves ◽  
Lee Wave ◽  
Eddy Field ◽  
The Impact

AbstractLee waves play an important role in transferring energy from the geostrophic eddy field to turbulent mixing in the Southern Ocean. As such, lee waves can impact the Southern Ocean circulation and modulate its response to changing climate through their regulation on the eddy field and turbulent mixing. The drag effect of lee waves on the eddy field and the mixing effect of lee waves on the tracer field have been studied separately to show their importance. However, it remains unclear how the drag and mixing effects act together to modify the Southern Ocean circulation. In this study, a lee wave parameterization that includes both lee wave drag and its associated lee-wave-driven mixing is developed and implemented in an eddy-resolving idealized model of the Southern Ocean to simulate and quantify the impacts of lee waves on the Southern Ocean circulation. The results show that lee waves enhance the baroclinic transport of the Antarctic Circumpolar Current (ACC) and strengthen the lower overturning circulation. The impact of lee waves on the large-scale circulation are explained by the control of lee wave drag on isopycnal slopes through their effect on eddies, and by the control of lee-wave-driven mixing on deep stratification and water mass transformation. The results also show that the drag and mixing effects are coupled such that they act to weaken one another. The implication is that the future parameterization of lee waves in global ocean and climate models should take both drag and mixing effects into consideration for a more accurate representation of their impact on the ocean circulation.

Turbulent mixing in uniform channels of irregular cross-section

1994 ◽  
Vol 32 (1) ◽  
pp. 67-86 ◽  
Author(s):  
R. I. Nokes ◽  
G. O. Hughes
Keyword(s):  
Cross Section ◽  
Turbulent Mixing
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