scholarly journals Accessing the Potential of Satellite and Telemetric Data to Evaluate the Influence of the Heat Flux Exchange in the Water Column Mixing and Stratification

2012 ◽  
Vol 03 (05) ◽  
pp. 899-907 ◽  
Author(s):  
Enner Alcântara
Keyword(s):  
Heat Flux ◽  
Water Column ◽  
Water Column Mixing

scholarly journals Physical processes of thermokarst lakes in the continuous permafrost zone of northern Siberia – observations and modeling (Lena River Delta, Siberia)

2015 ◽  
Vol 12 (8) ◽  
pp. 6637-6688 ◽  
Author(s):  
J. Boike ◽  
C. Georgi ◽  
G. Kirilin ◽  
S. Muster ◽  
K. Abramova ◽  
...  
Keyword(s):  
Heat Flux ◽  
Numerical Modeling ◽  
Water Column ◽  
River Water ◽  
Lena River ◽  
Thermokarst Lakes ◽  
Continuous Permafrost ◽  
Lake Bottom ◽  
Break Up ◽  
Lena River Delta

Abstract. The thermal regimes of five lakes located within the continuous permafrost zone of northern Siberia (Lena River Delta) have been investigated using hourly water temperature and water level records covering a three year period (2009–2012), together with bathymetric survey data. The lakes included thermokarst lakes located on Holocene river terraces that may be connected to Lena River water during spring flooding, and a thermokarst lake located on deposits of the Pleistocene Ice Complex. The data were used for numerical modeling with FLake software, and also to determine the physical indices of the lakes. The lakes vary in area, depths and volumes. The winter thermal regime is characterized by an ice cover up to 2 m thick that survives for more than 7 months of the year, from October until about mid-June. Lake-bottom temperatures increase at the start of the ice-covered period due to upward-directed heat flux from the underlying thawed sediment. The effects of solar radiation return prior to ice break-up, effectively warming the water beneath the ice cover and inducing convective mixing. Ice break-up starts the beginning of June and takes until the middle or end of June for completion. Mixing occurs within the entire water column from the start of ice break-up and continues during the ice-free periods, as confirmed by the Wedderburn numbers. Some of the lakes located closest to the Lena River are subjected to varying levels of spring flooding with river water, on an annual basis. Numerical modeling using FLake software indicates that the vertical heat flux across the bottom sediment tends towards an annual mean of zero, with maximum downward fluxes of about 5 W m−2 in summer and with heat released back into the water column at a~rate of less than 1 W m−2 during the ice-covered period. The lakes are shown to be efficient heat absorbers and effectively distribute the heat through mixing. Monthly bottom water temperatures during the ice-free period range up to 15 °C and are therefore higher than the associated monthly air or ground temperatures in the surrounding frozen permafrost landscape. The investigated lakes remain unfrozen at depth, with mean annual lake-bottom temperatures of between 2.7 and 4 °C. The data are available in the Supplement for this paper and through the PANGAEA website (http://www.pangaea.de/).

Decadal Sea Level Changes in the 50-Year GECCO Ocean Synthesis

2008 ◽  
Vol 21 (9) ◽  
pp. 1876-1890 ◽  
Author(s):  
Armin Köhl ◽  
Detlef Stammer
Keyword(s):  
Heat Flux ◽  
Sea Level Rise ◽  
Water Column ◽  
Sea Level ◽  
Ocean Circulation ◽  
Heat Content ◽  
Total Water ◽  
Sea Level Changes ◽  
Recent Estimate ◽  
Over The Top

Abstract An estimate of the time-varying ocean circulation, obtained over the period 1952–2001, is analyzed here with respect to its decadal and longer-term changes in sea level. The estimate results from a synthesis of most of the ocean datasets available during this 50-yr period with the Estimating the Circulation and Climate of the Ocean/Massachusetts Institute of Technology (ECCO/MIT) ocean circulation model. Over the period 1992 through 2001, the increase in thermosteric sea level rise on average amounts to 1.2 mm yr−1 over the top 750 m and 1.8 mm yr−1 over the total water column. This corresponds to an increase in upper-ocean heat content of 1.5 × 1022 J yr−1 and is in agreement with the estimates of Willis et al. However, over the period 1962 through 2001 the global net thermosteric sea level rise is estimated as 0.66 mm yr−1 over the top 750 m, which is twice the recent estimate from Antonov et al. (0.33 mm yr−1). The corresponding trend over the total water column of 0.92 mm yr−1 is also about twice their value for the layer of 0–3000 m (0.40 mm yr−1). For the last decade, the global heat flux into the ocean of 1.5 W m−2 is twice as large as the recent estimate by Willis et al. due to the heat content change in deeper layers. Regional changes in sea level are predominantly associated with an intensification of the subtropical gyre circulation and a corresponding redistribution of heat. The horizontal advection of heat due to an increase in wind stress curl is found to explain a major fraction of the estimated regional sea level trends over the last 40 years. However, the mechanisms appear different during the last decade when in some regions changes in surface heat flux may explain as much as 50% of the sea level changes.

scholarly journals CHANGE OF HEAT FLUX AT THE WATER-BOTTOM SEDIMENTS BOUNDARY IN A SMALL LAKE DURING THE YEAR

2021 ◽  
Vol 6(16) (4) ◽  
pp. 116-128
Author(s):  
G. E. Zdorovennova ◽  
G. G. Gavrilenko ◽  
N. I. Palshin ◽  
T. V. Efremova ◽  
S. R. Bogdanov ◽  
...  
Keyword(s):  
Heat Flux ◽  
Water Column ◽  
Bottom Sediments ◽  
Ice Formation ◽  
Heat Accumulation ◽  
Daily Frequency ◽  
Southern Karelia ◽  
Ice Period ◽  
Polymictic Lake ◽  
Water Bottom

The features of the variability of the heat flux at the boundary of the water column with bottom sediments in the central part of the small polymictic Lake Vendyurskoe (southern Karelia) were analyzed according to the data of year-round temperature measurements from November 2018 to October 2019. It was shown that the heat flux directed from the bottom sediments into the water reached 6–8 W/m2 in the pre-ice period and at the moments of ice formation and breaking, and did not exceed 1 W/m2 during most of the winter. A week after the ice-off (May 3–4, 2019) the water column was completely mixed, the heat flux changed its sign, and heat accumulation in the upper layer of bottom sediments began. The heat flux directed to bottom sediments was 4–6 W/m2, periodically increasing to 8-12 W/m2 from mid-May to late July and from the second decade of August to the first decade of September. Against the background of a prolonged cooling during the first ten days of August, the heat flux changed sign with daily frequency, the amplitude of daily fluctuations reached ± 2.5 W/m2. Autumn cooling of the Lake Vendyurskoe began in early September 2019, the heat flux sign changed on September 14–16, 2019.

scholarly journals Turbulence observations in the Gulf of Trieste under moderate wind forcing and different water column stratification

Ocean Science ◽  
2016 ◽  
Vol 12 (2) ◽  
pp. 433-449 ◽  
Author(s):  
Francesco Marcello Falcieri ◽  
Lakshmi Kantha ◽  
Alvise Benetazzo ◽  
Andrea Bergamasco ◽  
Davide Bonaldo ◽  
...  
Keyword(s):  
Heat Flux ◽  
Water Column ◽  
Adriatic Sea ◽  
Wind Forcing ◽  
Eastern Coast ◽  
Northern Coast ◽  
Northern Adriatic ◽  
Gulf Of Trieste ◽  
Open Sea ◽  
Vertical Density

Abstract. The oceanographic campaign CARPET2014 (Characterizing Adriatic Region Preconditionig EvenTs), (30 January–4 February 2014) collected the very first turbulence data in the Gulf of Trieste (northern Adriatic Sea) under moderate wind (average wind speed 10 m s−1) and heat flux (net negative heat flux ranging from 150 to 400 W m−2). Observations consisted of 38 CTD (Conductivity, Temperature, Depth) casts and 478 microstructure profiles (grouped into 145 ensembles) with three sets of yoyo casts, each lasting for about 12 consecutive hours. Averaging closely repeated casts, such as the ensembles, can lead to a smearing effect when in the presence of a vertical density structure with strong interfaces that can move up or down between subsequent casts under the influence of tides and internal waves. In order to minimize the smearing effect of such displacements on mean quantities, we developed an algorithm to realign successive microstructure profiles to produce sharper and more meaningful mean profiles of measured turbulence parameters. During the campaign, the water column in the gulf evolved from well-mixed to stratified conditions due to Adriatic waters intruding at the bottom along the gulf's south-eastern coast. We show that during the warm and relatively dry winter, the water column in the Gulf of Trieste, even under moderate wind forcing, was not completely mixed due to the influence of bottom waters intruding from the open sea. Inside the gulf, two types of water intrusions were found during yoyo casts: one coming from the northern coast of the Adriatic Sea (i.e. cooler, fresher and more turbid) and one coming from the open sea in front of the Po Delta (i.e. warmer, saltier and less turbid). The two intrusions had different impacts on turbulence kinetic energy dissipation rate profiles. The former, with high turbidity, acted as a barrier to wind-driven turbulence, while the latter, with low sediment concentrations and a smaller vertical density gradient, was not able to suppress downward penetration of turbulence from the surface.

Sign in / Sign up

Export Citation Format

Share Document