Analysis of horizontal and vertical processes contributing to natural iron supply in the mixed layer in southern Drake Passage

2013 ◽  
Vol 90 ◽  
pp. 68-76 ◽  
Author(s):  
Marina Frants ◽  
Sarah T. Gille ◽  
Mariko Hatta ◽  
William T. Hiscock ◽  
Mati Kahru ◽  
...  
Keyword(s):  
Mixed Layer ◽  
Drake Passage ◽  
Iron Supply ◽  
Natural Iron

scholarly journals Imprint of a dissolved cobalt basaltic source on the Kerguelen Plateau

2012 ◽  
Vol 9 (12) ◽  
pp. 5279-5290 ◽  
Author(s):  
J. Bown ◽  
M. Boye ◽  
P. Laan ◽  
A. R. Bowie ◽  
Y.-H. Park ◽  
...  
Keyword(s):  
Surface Waters ◽  
External Input ◽  
Eastern Slope ◽  
Kerguelen Plateau ◽  
Dissolved Iron ◽  
Deep Waters ◽  
Iron Supply ◽  
Natural Iron ◽  
Shelf Sediments ◽  
Lateral Advection

Abstract. Processes of cobalt (Co) entrainment from shelf sediments over the Kerguelen Plateau were studied during the KEOPS (Kerguelen Ocean Plateau compared Study) in order to explain the exceptionally high dissolved cobalt concentrations that have been measured in the surface waters above the Kerguelen Plateau, and in intermediate and deep waters above its eastern slope. Lateral advection and dissolution of Co contained in basalt sediments around Heard Island, a main source of lithogenic Co in the study area, were shown to imprint the process of surface enrichment over the plateau. Dissolved Co enrichment was strongest at the intercept of the eastern slope with intermediate and deep waters, probably due to more efficient mobilisation of the sediments in the slope current, in addition to advection of Co-enriched and low-oxygenated ocean water masses. In surface waters, the strong sedimentary Co inputs were estimated to be much higher than biological Co uptake in phytoplankton blooms, underlining the potential use of dissolved cobalt as tracer of the natural iron fertilization above the Kerguelen Plateau. Based on a simple steady-state balance equation of the external input of dissolved iron over the plateau, the fertilization of iron inferred by using dissolved Co as a tracer of basalt sources is estimated to be 28 × 102 ± 21 × 102 t yr−1 in surface waters of the Kerguelen Plateau. This estimate is consistent with preceding ones (Zhang et al., 2008; Chever et al., 2010), and the calculated iron supply matches with the phytoplankton demand (Sarthou et al., 2008).

scholarly journals Significant mixed layer nitrification in a natural iron-fertilized bloom of the Southern Ocean

2015 ◽  
Vol 29 (11) ◽  
pp. 1929-1943 ◽  
Author(s):  
F. Fripiat ◽  
M. Elskens ◽  
T. W. Trull ◽  
S. Blain ◽  
A. -J. Cavagna ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Mixed Layer ◽  
Natural Iron

scholarly journals Shear at the Base of the Oceanic Mixed Layer Generated by Wind Shear Alignment

2013 ◽  
Vol 43 (8) ◽  
pp. 1798-1810 ◽  
Author(s):  
Liam Brannigan ◽  
Yueng-Djern Lenn ◽  
Tom P. Rippeth ◽  
Elaine McDonagh ◽  
Teresa K. Chereskin ◽  
...  
Keyword(s):  
Mixed Layer ◽  
Wind Shear ◽  
High Spatial Resolution ◽  
Layer Structure ◽  
Drake Passage ◽  
Velocity Data ◽  
Ocean Mixed Layer ◽  
Shear Alignment ◽  
Simple Theoretical Model ◽  
Wind Driven Currents

Abstract Observations are used to evaluate a simple theoretical model for the generation of near-inertial shear spikes at the base of the open ocean mixed layer when the upper ocean displays a two-layer structure. The model predicts that large changes in shear squared can be produced by the alignment of the wind and shear vectors. A climatology of stratification and shear variance in Drake Passage is presented, which shows that these assumptions are most applicable to summer, fall, and spring but are not highly applicable to winter. Temperature, salinity, and velocity data from a high spatial resolution cruise in Drake Passage show that the model does not predict all large changes in shear variance; the model is most effective at predicting changes in shear squared when it arises owing to near-inertial wind-driven currents without requiring a rotating resonant wind stress. The model is also more effective where there is a uniform mixed layer above a strongly stratified transition layer. Rotary spectral and statistical analysis of an additional 242 Drake Passage transects from 1999 to 2011 confirmed the presence of this shear-spiking mechanism, particularly in summer, spring, and fall when stratification is stronger.

scholarly journals Frontal Circulation and Submesoscale Variability during the Formation of a Southern Ocean Mesoscale Eddy

2017 ◽  
Vol 47 (7) ◽  
pp. 1737-1753 ◽  
Author(s):  
Katherine A. Adams ◽  
Philip Hosegood ◽  
John R. Taylor ◽  
Jean-Baptiste Sallée ◽  
Scott Bachman ◽  
...  
Keyword(s):  
Mixed Layer ◽  
Mesoscale Eddy ◽  
Drake Passage ◽  
Mathematical Framework ◽  
Intermediate Water ◽  
Surface Mixed Layer ◽  
Mode Water ◽  
Scotia Sea ◽  
Simplifying Assumptions ◽  
Circumpolar Current

AbstractObservations made in the Scotia Sea during the May 2015 Surface Mixed Layer Evolution at Submesoscales (SMILES) research cruise captured submesoscale, O(1–10) km, variability along the periphery of a mesoscale O(10–100) km meander precisely as it separated from the Antarctic Circumpolar Current (ACC) and formed a cyclonic eddy ~120 km in diameter. The meander developed in the Scotia Sea, an eddy-rich region east of the Drake Passage where the Subantarctic and Polar Fronts converge and modifications of Subantarctic Mode Water (SAMW) occur. In situ measurements reveal a rich submesoscale structure of temperature and salinity and a loss of frontal integrity along the newly formed southern sector of the eddy. A mathematical framework is developed to estimate vertical velocity from collocated drifter and horizontal water velocity time series, under certain simplifying assumptions appropriate for the current dataset. Upwelling (downwelling) rates of O(100) m day−1 are found in the northern (southern) eddy sector. Favorable conditions for submesoscale instabilities are found in the mixed layer, particularly at the beginning of the survey in the vicinity of density fronts. Shallower mixed layer depths and increased stratification are observed later in the survey on the inner edge of the front. Evolution in temperature–salinity (T–S) space indicates modification of water mass properties in the upper 200 m over 2 days. Modifications along σθ = 27–27.2 kg m−3 have climate-related implications for mode and intermediate water transformation in the Scotia Sea on finer spatiotemporal scales than observed previously.

scholarly journals Abrupt Transitions in Submesoscale Structure in Southern Drake Passage: Glider Observations and Model Results

2018 ◽  
Vol 48 (9) ◽  
pp. 2011-2027 ◽  
Author(s):  
Giuliana A. Viglione ◽  
Andrew F. Thompson ◽  
M. Mar Flexas ◽  
Janet Sprintall ◽  
Sebastiaan Swart
Keyword(s):  
Mixed Layer ◽  
Spatial Scales ◽  
Mesoscale Eddy ◽  
Drake Passage ◽  
One Dimensional ◽  
Ocean Stratification ◽  
Eddy Field ◽  
Shackleton Fracture Zone ◽  
Different Characteristics

AbstractEnhanced vertical velocities associated with submesoscale motions may rapidly modify mixed layer depths and increase exchange between the mixed layer and the ocean interior. These dynamics are of particular importance in the Southern Ocean, where the ventilation of many density classes occurs. Here we present results from an observational field program in southern Drake Passage, a region preconditioned for submesoscale instability owing to its strong mesoscale eddy field, persistent fronts, strong down-front winds, and weak vertical stratification. Two gliders sampled from December 2014 through March 2015 upstream and downstream of the Shackleton Fracture Zone (SFZ). The acquired time series of mixed layer depths and buoyancy gradients enabled calculations of potential vorticity and classifications of submesoscale instabilities. The regions flanking the SFZ displayed remarkably different characteristics despite similar surface forcing. Mixed layer depths were nearly twice as deep, and horizontal buoyancy gradients were larger downstream of the SFZ. Upstream of the SFZ, submesoscale variability was confined to the edges of topographically steered fronts, whereas downstream these motions were more broadly distributed. Comparisons to a one-dimensional (1D) mixing model demonstrate the role of submesoscale instabilities in generating mixed layer variance. Numerical output from a submesoscale-resolving simulation indicates that submesoscale instabilities are crucial for correctly reproducing upper-ocean stratification. These results show that bathymetry can play a key role in generating dynamically distinct submesoscale characteristics over short spatial scales and that submesoscale motions can be locally active during summer months.

TEMPERATURE VARIABILITY AT SENUNU BAY, WEST SUMBAWA

2013 ◽  
Vol 5 (2) ◽  
Author(s):  
Syamsul Hidayat ◽  
Mulia Purba ◽  
Jorina Waworuntu
Keyword(s):  
Layer Thickness ◽  
Mixed Layer ◽  
Cross Correlation ◽  
Sea Surface ◽  
Thermocline Depth ◽  
Kelvin Wave ◽  
The West ◽  
Sea Bottom ◽  
Annual Period ◽  
Regional Processes

The purposes of this study were to determine the variability of temperature and its relation to regional processes in the Senunu Bay. The result showed clear vertical stratifications i.e., mixed layer thickness about 39-119 m with isotherm of 27°C, thermocline layer thickness about 83-204 m with isotherm of 14–26°C, and  the deeper layer from the thermocline lower limit to the sea bottom with isotherm <13°C. Temperature and the thickness of each layers varied with season in which during the Northwest Monsoon the temperature was warmer and the mixed layer was thicker than those during Southeast Monsoon. During Southeast Monsoon, the thermocline layer rose  about 24 m. The 2001, 2006, and 2009 (weak La Nina years),  the Indonesia Throughflow (ITF) carried warmer water, deepening thermocline depth and reducing upwelling strength.  In 2003 and 2008 thickening of mixed layer occurred in transition season  was believed  associated with the  arrival of Kelvin Wave from the west. In 2002 and 2004 (weak El Nino period,) ITF carries colder water shallowing thermocline depth and enhancing upwelling strength. In 2007 was believed to be related with positive IODM where the sea surface temperature were decreasing due to intensification of southeast wind which induced strong upwelling. The temperature spectral density of mixed layer and thermocline was influenced by annual, semi-annual, intra-annual and inter-annual period fluctuations. The cross-correlation between wind and temperature showed significant value in the annual period.  Keywords: temperature, thermocline, variability, ENSO, IODM.

DEMINERALIZATION OF WATER WITH MIXED-LAYER ION-EXCHANGERS

2013 ◽  
Vol 12 (1) ◽  
pp. 137-145 ◽  
Author(s):  
Iuliana Rogoveanu Radosavlevici ◽  
Dan Niculae Robescu
Keyword(s):  
Mixed Layer ◽  
Ion Exchangers
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