scholarly journals Symmetrical and Asymmetrical Rectifications Employed for Deeper Ocean Extrapolations of In Situ CTD Data and Subsequent Sound Speed Profiles

Symmetry ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1455
Author(s):  
Kashif Iqbal ◽  
Minghui Zhang ◽  
Shengchun Piao
Keyword(s):  
Ocean Circulation ◽  
Sound Speed ◽  
Transmission Loss ◽  
Spatial Scales ◽  
Deep Ocean ◽  
The United States ◽  
Critical Parameters ◽  
Argo Data ◽  
Argo Floats

The multinational Argo program, which was initiated in 1999, has completed its global requirement of 3000 floats deployed by 2007. This program has revolutionized ocean observations with the provision of varying data in the upper half of the ocean. However, various studies have reiterated the requirement for deep ocean coverage, since the ocean below 2000 meters (m) is warming. In this regard, full-depth studies are mandatory in order to estimate the rising sea level due to thermal expansion and analyze critical parameters of deep ocean circulation sub 2000 m; further, data below 2000 m are mandatory for multifarious model simulations. As a landmark initiative, in mid-2015, the “Deep Argo Implementation Workshop” was held in Hobart. An array comprising 1228 floats was suggested by G. C. Johnson, rendering coverage of 5° latitude × 5° longitude × 15-day cycles. This was conclusively agreed to be an affordable solution for varying scientific needs for assessing data in abyssal oceans. Thence, Deep New profilINg float of JApan (NINJA) and Deep Arvor floats were developed by Japan and France, respectively, to cover depths of 0–4000 m. Similarly, Deep Autonomous Profiling Explorer (APEX) and Deep Sounding Oceanographic Lagrangian Observer (SOLO) by the United States were designed to cover 0–6000 m. The data offered by this underdeveloped deep pilot array are scarce on both temporal and spatial scales. This particular study offers an ingenious and novel approach to extrapolating conductivity–temperature–depth (CTD) profiles, as well as sound speed profiles (SSPs), in abyssal oceans below 2000 m. The primitive results of this method exhibited certain discrepancies which were subsequently rectified by modifying the aforementioned method both symmetrically and asymmetrically in an innovative way. The final outcomes of this method are almost identical to the in situ values obtained from Deep Argo floats, and in this way, offer a way to compute deep ocean calculations both spatially and temporally since Deep Argo floats are aimed at relatively sparse deployments and require a longer duration to provide data (5° latitude × 5° longitude × 15-day cycles) as compared to Core Argo data (3° latitude × 3° longitude × 10-day cycles). The SSP computations were conducted by employing multiple equations such as Chen and Millero, Del Grosso, and UNESCO (United Nations Educational, Scientific, and Cultural Organization) algorithms. The study concludes by offering transmission loss rectifications by employing the aforementioned method as a future course of action.

scholarly journals Spatial scales of temperature and salinity variability estimated from Argo observations

2015 ◽  
Vol 12 (4) ◽  
pp. 1793-1814
Author(s):  
F. Ninove ◽  
P. Y. Le Traon ◽  
E. Remy ◽  
S. Guinehut
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Deep Ocean ◽  
General Tendency ◽  
Zero Crossing ◽  
Tropical Regions ◽  
Covariance Functions ◽  
Salinity Variability ◽  
First Time

Abstract. Argo observations from 2005 to 2013 are used to characterize spatial scales temperature and salinity variations from the surface down to 1500 m. Simulations are first performed to analyze the sensitivity of results to Argo sampling; they show that several years of Argo observations are required to estimate the spatial scales of ocean variability over 20° × 20° boxes. Spatial scales are then computed over several large scale areas. Zonal and meridional spatial scales (Lx and Ly which are also zero crossing of covariance functions) vary as expected with latitudes. Scales are of about 100 km at high latitudes and more of 700 km in the Indian and Pacific equatorial/tropical regions. Zonal and meridional scales are similar: except in these tropical/equatorial regions where zonal scales are much larger (by a factor of 2 to 3) than meridional scales. Spatial scales are the largest close to the surface and have a general tendency for temperature to increase in deeper layers. There are significant differences between temperature and salinity scales, in particular, in the deep ocean. Results are consistent with previous studies based on sparse in-situ observations or satellite altimetry. They provide, however, for the first time a global description of temperature and salinity scales of variability and a characterization of their variations according to depths.

Shifting ocean circulation warms the Subpolar North Atlantic since 2016

2021 ◽  
Author(s):  
Damien Desbruyères ◽  
Léon Chafik ◽  
Guillaume Maze
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Large Scale ◽  
Deep Ocean ◽  
Ocean Heat Uptake ◽  
Driving Mechanisms ◽  
Temperature Trends ◽  
Meridional Overturning ◽  
Ocean Observing

<p>The Subpolar North Atlantic (SPNA) is known for rapid reversals of decadal temperature trends, with ramifications encompassing the large-scale meridional overturning and gyre circulations, Arctic heat and mass balances, or extreme continental weather. Here, we combine datasets derived from sustained ocean observing systems (satellite and in situ), and idealized observation-based modelling (advection-diffusion of a passive tracer) and machine learning technique (ocean profile clustering) to document and explain the most-recent and ongoing cooling-to-warming transition of the SPNA. Following a gradual cooling of the region that was persisting since 2006, a surface-intensified and large-scale warming sharply emerged in 2016 following an ocean circulation shift that enhanced the northeastward penetration of warm and saline waters from the western subtropics. Driving mechanisms and ramification for deep ocean heat uptake will be discussed.</p>

scholarly journals Spatial scales of temperature and salinity variability estimated from Argo observations

Ocean Science ◽  
2016 ◽  
Vol 12 (1) ◽  
pp. 1-7 ◽  
Author(s):  
F. Ninove ◽  
P.-Y. Le Traon ◽  
E. Remy ◽  
S. Guinehut
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Deep Ocean ◽  
General Tendency ◽  
Zero Crossing ◽  
Tropical Regions ◽  
Covariance Functions ◽  
Salinity Variability ◽  
First Time

Abstract. Argo observations from 2005 to 2013 are used to characterize spatial scales of temperature and salinity variations from the surface down to 1300 m. Simulations are first performed to analyze the sensitivity of results to Argo sampling; they show that several years of Argo observations are required to estimate spatial scales of ocean variability over 20°  ×  20° boxes. Spatial scales are then computed over several large-scale areas. Zonal and meridional spatial scales (Lx and Ly which are zero crossing of covariance functions) vary as expected with latitudes. Scales are of about 100 km at high latitudes and more of 700 km in the Indian and Pacific equatorial–tropical regions. Zonal and meridional scales are similar except in tropical–equatorial regions where zonal scales are much larger (by a factor of 2 to 3) than meridional scales. Spatial scales are the largest close to the surface and have a general tendency for temperature to increase in deeper layers. There are significant differences between temperature and salinity scales, in particular, in the deep ocean. Results are consistent with previous studies based on sparse in situ observations or satellite altimetry. They provide, however, for the first time a global description of temperature and salinity scales of variability and a characterization of their variations according to depths.

scholarly journals Label-Free Bacterial Imaging with Deep-UV-Laser-Induced Native Fluorescence

2010 ◽  
Vol 76 (21) ◽  
pp. 7231-7237 ◽  
Author(s):  
Rohit Bhartia ◽  
Everett C. Salas ◽  
William F. Hug ◽  
Ray D. Reid ◽  
Arthur L. Lane ◽  
...  
Keyword(s):  
Fluorescent Dyes ◽  
Spatial Scales ◽  
Single Cells ◽  
Deep Ocean ◽  
Imaging Method ◽  
Label Free ◽  
Deep Biosphere ◽  
Native Fluorescence ◽  
Deep Uv

ABSTRACT We introduce a near-real-time optical imaging method that works via the detection of the intrinsic fluorescence of life forms upon excitation by deep-UV (DUV) illumination. A DUV (<250-nm) source enables the detection of microbes in their native state on natural materials, avoiding background autofluorescence and without the need for fluorescent dyes or tags. We demonstrate that DUV-laser-induced native fluorescence can detect bacteria on opaque surfaces at spatial scales ranging from tens of centimeters to micrometers and from communities to single cells. Given exposure times of 100 μs and low excitation intensities, this technique enables rapid imaging of bacterial communities and cells without irreversible sample alteration or destruction. We also demonstrate the first noninvasive detection of bacteria on in situ-incubated environmental experimental samples from the deep ocean (Lo'ihi Seamount), showing the use of DUV native fluorescence for in situ detection in the deep biosphere and other nutrient-limited environments.

scholarly journals A global comparison of Argo and satellite altimetry observations

2010 ◽  
Vol 7 (3) ◽  
pp. 995-1015 ◽  
Author(s):  
A.-L. Dhomps ◽  
S. Guinehut ◽  
P.-Y. Le Traon ◽  
G. Larnicol
Keyword(s):  
Ocean Circulation ◽  
Large Scale ◽  
Low Frequency ◽  
Deep Ocean ◽  
Reference Level ◽  
High Latitudes ◽  
Argo Data ◽  
Sea Level Anomalies ◽  
Global Comparison ◽  
Spatial Coverage

Abstract. Differences and complementarities between Sea Level Anomalies (SLA) deduced from altimeter measurements and dynamic height anomalies (DHA) calculated from Argo in situ temperature (T) and salinity (S) profiles are globally analyzed. Compared to previous studies, Argo data allows a much better spatial coverage of all oceans and particularly the Southern Ocean, the use of salinity measurements and the use of a deeper reference level. The use of time series along the Argo float trajectories also provides a means to describe the vertical structure of the ocean both for the low frequency and the mesoscale part of the circulation. The comparison shows the very good consistency between Argo and altimeter observations. Correlations range from 0.9 in low latitudes to 0.3 in high latitudes where the contributions of deep baroclinic and barotropic signals are the largest. The study underlines the large influence of salinity observations on the consistency between altimetry and hydrographic observations. SLA/DHA consistency is thus improved by 35% (relative to the SLA minus DHA signal) by using measured S profiles instead of climatology data. The use of a deep reference level also significantly improves the correlation at mid and high latitudes. The role of seasonal signals on the correlation and regression analysis between altimeter and Argo observations is also analyzed. As they are mainly associated with the heating/cooling of surface layers, removing these large scale signals significantly reduces the correlation and impacts the geographical structure of the Argo/altimetry regression coefficients. These results emphasize the need to separate the different time and space scales in order to improve the merging of the two data sets. The study of seasonal to interannual SLA minus DHA signals finally reveals interesting signals related to deep ocean circulation variations. Future work is, however, needed to understand the observed differences and relate them to different forcing mechanisms.

A geodetic approach to Mapping and Parametrization of Argo Temperature and Salinity Profiles

2021 ◽  
Author(s):  
Alisa Yakhontova ◽  
Roelof Rietbroek ◽  
Sophie Stolzenberger ◽  
Nadja Jonas
Keyword(s):  
Ocean Circulation ◽  
Circulation Model ◽  
Deep Ocean ◽  
The Arctic ◽  
Argo Data ◽  
Mapping Procedure ◽  
Covariance Functions ◽  
Temporal Sampling ◽  
Spatio Temporal ◽  
Sampling Problems

&lt;p&gt;This study addresses mapping of Argo temperature and salinity profiles onto arbitrary positions using physically advanced statistical information from model fields, and their subsequent parametrization as function of depth. Argo suffers from spatio-temporal sampling problems, and some signals are not well captured, e.g. in the deeper ocean below 2000m, around the boundary currents, in the Arctic or in the shelf/coastal regions which are not frequently visited by floats. Mapping of Argo data into sparsely sampled areas would greatly benefit from additional physical information of coherent T/S behavior in form of covariance functions. Outputs from global general ocean circulation model FESOM1.4 provide covariance information for least squares collocation and also complement the spatially undersampled Argo data in high latitudes and in deep ocean. Additionally, model covariances are used to identify areas of strong correlation with interpolation points, so that only Argo measurements inside these areas are included in the mapping procedure. Parametrization of T/S profiles is performed with b-splines where the choice of knot locations is a trade-off between accuracy and overfitting. Proposed methodology is tested in South Atlantic, but can be extended to other regions.&lt;/p&gt;

scholarly journals Spatial and Temporal Scales of Sverdrup Balance*

2014 ◽  
Vol 44 (10) ◽  
pp. 2644-2660 ◽  
Author(s):  
Matthew D. Thomas ◽  
Agatha M. De Boer ◽  
Helen L. Johnson ◽  
David P. Stevens
Keyword(s):  
Ocean Circulation ◽  
Climate Model ◽  
Spatial Scales ◽  
Deep Ocean ◽  
Western Boundary ◽  
Meridional Transport ◽  
Temporal Scales ◽  
State Estimate ◽  
Spatial And Temporal Scales ◽  
Sverdrup Balance

Abstract Sverdrup balance underlies much of the theory of ocean circulation and provides a potential tool for describing the interior ocean transport from only the wind stress. Using both a model state estimate and an eddy-permitting coupled climate model, this study assesses to what extent and over what spatial and temporal scales Sverdrup balance describes the meridional transport. The authors find that Sverdrup balance holds to first order in the interior subtropical ocean when considered at spatial scales greater than approximately 5°. Outside the subtropics, in western boundary currents and at short spatial scales, significant departures occur due to failures in both the assumptions that there is a level of no motion at some depth and that the vorticity equation is linear. Despite the ocean transport adjustment occurring on time scales consistent with the basin-crossing times for Rossby waves, as predicted by theory, Sverdrup balance gives a useful measure of the subtropical circulation after only a few years. This is because the interannual transport variability is small compared to the mean transports. The vorticity input to the deep ocean by the interaction between deep currents and topography is found to be very large in both models. These deep transports, however, are separated from upper-layer transports that are in Sverdrup balance when considered over large scales.

The CMEMS In Situ TAC multi-year and multi-variate products to monitor and understand the ocean variability

2021 ◽  
Author(s):  
Tanguy Szekely ◽  
Mélanie Juza ◽  
Jérôme Gourrion ◽  
Paz Rotllán-García ◽  
Sylvie Pouliquen ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Marine Ecosystem ◽  
Deep Ocean ◽  
Global Ocean ◽  
Polar Regions ◽  
Temporal Scales ◽  
Essential Information ◽  
The Impact

&lt;p&gt;The CMEMS In Situ TAC (INSTAC) integrates &lt;em&gt;in situ&lt;/em&gt; observations from various platforms, (e.g. profiling floats, gliders, drifters, saildrones, research vessels, ferryboxes, fixed stations, tides gauges, sea mammals, high-frequency radar), providing physical and biogeochemical ocean data at local, regional and global scales, with an increasing data integration from the polar and coastal regions.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;The INSTAC quality-controlled data in both delayed mode and near-real time are contributing to support the operational oceanography (e.g. model forecasting, analysis and reanalysis, satellite calibration, downstream services) and to monitor the 4-dimensional ocean at various spatial and temporal scales. The INSTAC multi-year products provide an essential information on the ocean state, variability and changes and allow addressing long-term variations (climate) analysis as well as detecting remarkable events. Hence, the INSTAC group has contributed substantially to the elaboration of the annual CMEMS Ocean State Report (OSR, &lt;em&gt;Von Schuckmann et al.&lt;/em&gt;, 2016, 2018, 2019, 2020, 2021).&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;A general overview of the INSTAC contributions to the CMEMS OSR is presented, highlighting its capacity to describe, analyze and understand the ocean state and variability of both physical and biogeochemical components from the sea surface to the deep ocean, from the coastal to open sea waters, from tropical to polar regions, from semi-enclosed seas to the global ocean, from short-term to long-term temporal scales. The INSTAC team contributes to the CMEMS Ocean Monitoring Indicators reporting, investigates the ocean circulation variability, analyses the impact of climate change on marine ecosystem and ocean circulation, and develops operational applications and services.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Maintaining the current observational network, integrating new platforms, enhancing the spatial and temporal resolutions, improving methodologies and developing new metrics (e.g. quality control, data assimilation), developing new products, INSTAC will continue to serve the overall need to understand and predict the ocean state and variability, in line with the present and future scientific, societal and environmental challenges.&lt;/p&gt;

scholarly journals Decadal Spatiotemporal Halocline Analysis by ISAS15 Due to Influx of Major Rivers in Oceans and Discrepancies Illustrated Near the Bay of Bengal

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2886
Author(s):  
Kashif Iqbal ◽  
Shengchun Piao ◽  
Minghui Zhang
Keyword(s):  
Bay Of Bengal ◽  
Sound Speed ◽  
Yangtze Estuary ◽  
Argo Data ◽  
Course Of Action ◽  
Novel Approach ◽  
Ocean Salinity ◽  
Analysis System ◽  
Major Factors

The discharge from rivers is one of the major factors of regional salinity perturbations in addition to precipitation, evaporation, and circulation of the ocean, whereas simulations regarding the marine environment are dominantly affected by ocean salinity. Moreover, perturbations in the timing and quantity of freshwater cause salinity fluctuations, which in turn, affect the communities of both plant and fauna. In this regard, the study ingeniously employs In Situ Analysis System-15 (ISAS15) data, which is freely available online, to ascertain the salinities in proximity of the major rivers around the globe. Such computations are multilayered, i.e., for 1, 3, 5, and 10 m, and conducted along major freshwater influxes, i.e., the Amazon River, Bay of Bengal (BoB), and Yangtze River, on decadal scales, i.e., in 2004 and in 2014. Depending upon the location and availability of ISAS-15 data, the area in proximity of the Amazon is analyzed horizontally, vertically, and obliquely, whereas the areas in proximity of the BoB and Yangtze estuary are analyzed vertically and obliquely. Similarly, the study analyzed the freshwater influx at the aforementioned locations both for the maxima and minima, i.e., during the particular months that observed the maximum and minimum influx into the ocean from the above-mentioned freshwater sources in 2004, as well as in 2014. The detailed analysis proved the outcomes to be conforming with the documented literary data along the Amazon and Yangtze estuaries. However, the computed analysis illustrated the anomalous values in proximity of the BoB. The study proceeds to discuss an ingenious approach of computing, as well as extrapolating, the salinities, temperatures, and sound speed profiles (SSPs) by employing in situ deep Argo data in order to counter such anomalies, as well as conjoin it with ISAS data, to investigate such regions with broader spatiotemporal capabilities for the future course of action. For this particular study, this method is employed on certain Argo buoys in order to prove the efficacy of the aforementioned novel approach.

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