scholarly journals Global dataset of thermohaline staircases obtained from Argo floats and Ice Tethered Profilers

2020 ◽  
Author(s):  
Carine G. van der Boog ◽  
J. Otto Koetsier ◽  
Henk A. Dijkstra ◽  
Julie D. Pietrzak ◽  
Caroline A. Katsman

Abstract. Thermohaline staircases arise from double diffusive processes. They are characterised by stepped structures consisting of mixed layers of typically tens of meters thick that are separated by much thinner gradient layers. Through these gradient layers enhanced diapycnal salt and heat transport take place. In this study, we present a global dataset of thermohaline staircases derived from observations of Argo profiling floats and Ice Tethered Profilers using a novel detection algorithm. To establish the presence of stepped thermohaline staircases, the algorithm detects subsurface mixed layers and analyses the gradient layers in between. Of each detected staircase, the temperature, salinity, depth and height, as well as some other properties of the mixed layers and gradient layers are computed. The algorithm is applied to 487,647 quality-controlled temperature and salinity profiles to obtain the global dataset. The performance of the algorithm is verified through an analysis of independent regional observations. The algorithm and global dataset are available at the 4TU centre for research data (van der Boog et al. 10 (2020), doi: https://doi.org/10.4121/uuid:f6529d31-b285-46ac-990b-5f45839f4e11).

2021 ◽  
Vol 13 (1) ◽  
pp. 43-61 ◽  
Author(s):  
Carine G. van der Boog ◽  
J. Otto Koetsier ◽  
Henk A. Dijkstra ◽  
Julie D. Pietrzak ◽  
Caroline A. Katsman

Abstract. Thermohaline staircases are associated with double-diffusive mixing. They are characterized by stepped structures consisting of mixed layers of typically tens of metres thick that are separated by much thinner interfaces. Through these interfaces enhanced diapycnal salt and heat transport take place. In this study, we present a global dataset of thermohaline staircases derived from observations of Argo profiling floats and Ice-Tethered Profilers using a novel detection algorithm. To establish the presence of thermohaline staircases, the algorithm detects subsurface mixed layers and analyses the interfaces in between. Of each detected staircase, the conservative temperature, absolute salinity, depth, and height, as well as some other properties of the mixed layers and interfaces, are computed. The algorithm is applied to 487 493 quality-controlled temperature and salinity profiles to obtain a global dataset. The performance of the algorithm is verified through an analysis of independent regional observations. The algorithm and global dataset are available at https://doi.org/10.5281/zenodo.4286170.


2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Carine G. van der Boog ◽  
Henk A. Dijkstra ◽  
Julie D. Pietrzak ◽  
Caroline A. Katsman

AbstractDouble-diffusive processes enhance diapycnal mixing of heat and salt in the open ocean. However, observationally based evidence of the effects of double-diffusive mixing on the global ocean circulation is lacking. Here we analyze the occurrence of double-diffusive thermohaline staircases in a dataset containing over 480,000 temperature and salinity profiles from Argo floats and Ice-Tethered Profilers. We show that about 14% of all profiles contains thermohaline staircases that appear clustered in specific regions, with one hitherto unknown cluster overlying the westward flowing waters of the Tasman Leakage. We estimate the combined contribution of double-diffusive fluxes in all thermohaline staircases to the global ocean’s mechanical energy budget as 7.5 GW [0.1 GW; 32.8 GW]. This is small compared to the estimated energy required to maintain the observed ocean stratification of roughly 2 TW. Nevertheless, we suggest that the regional effects, for example near Australia, could be pronounced.


2014 ◽  
Vol 44 (1) ◽  
pp. 289-296 ◽  
Author(s):  
J. R. Carpenter ◽  
M.-L. Timmermans

Abstract The diffusive (or semiconvection) regime of double-diffusive convection (DDC) is widespread in the polar oceans, generating “staircases” consisting of high-gradient interfaces of temperature and salinity separated by convectively mixed layers. Using two-dimensional direct numerical simulations, support is provided for a previous theory that rotation can influence DDC heat fluxes when the thickness of the thermal interface sufficiently exceeds that of the Ekman layer. This study finds, therefore, that the earth’s rotation places constraints on small-scale vertical heat fluxes through double-diffusive layers. This leads to departures from laboratory-based parameterizations that can significantly change estimates of Arctic Ocean heat fluxes in certain regions, although most of the upper Arctic Ocean thermocline is not expected to be dominated by rotation.


Author(s):  
Shahanaz Parvin ◽  
Siti Suzilliana Putri Mohamed Isa ◽  
Wasim Jamshed ◽  
Rabha W. Ibrahim ◽  
Kottakkaran Sooppy Nisar

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