A New Estimate of Global Ocean Climatology

2021 ◽  
Author(s):  
Kanwal Shahzadi ◽  
Nadia Pinardi ◽  
Marco Zavaterelli ◽  
Simona Simoncelli
Keyword(s):  
Quality Control ◽  
World Ocean ◽  
Global Ocean ◽  
Physical Parameters ◽  
Oxygen Utilization ◽  
Non Linear ◽  
Using Data ◽  
The Impact ◽  
Apparent Oxygen Utilization

<p>The estimation of climatology is a key element for improving our understanding of the ocean state. Historical data sets available today enables an almost complete reconstruction of global ocean fields. In this study, a new global ocean climatological estimate of basic physical parameters such as temperature, salinity, density, dissolved oxygen, and apparent oxygen utilization is computed using the World Ocean Database (WOD18). The reliability of estimate is closely tied to the quality assurance of the in-situ observations and statistical interpolation schemes of the mapping. Therefore, in this context, WOD18 used for this study has gone through a non-linear quality control procedure developed by Shahzadi (2020) on a global domain. The mapping of resulting data is carried out using Data Interpolating Variational Analysis (DIVA). Sensitivity experiments are carried out to choose the key parameters of DIVA, namely the horizontal correlation lengths, and the Noise to Signal ratio (N/S). Furthermore, two new indices such as roughness index, and root mean square of residuals are designed to show the impact of the correlation length, and N/S ratio choices. For temperature and salinity, two different versions of the climatological estimates are produced: (i) a long-term (1900 to 2017) climatology using multiple platforms in-situ data, and (ii) a shorter time estimate (2003-2017) using data from ocean drifting platforms such as profiling floats. The two versions are intercompared and differences are evaluated.  Similar procedures are applied for global mapping of Density, Oxygen, and Apparent Oxygen utilization. The new climatological estimates are compared with previous estimates such as World Ocean Atlas and World Argo Global Hydrographic climatological estimates, and thereby the differences are analysed.</p><p><strong>Keywords:</strong> WOD18, temperature, salinity, apparent oxygen, DIVA, climatology, non-linear quality control.</p><p>Shahzadi, K., (2020): “A New Global Ocean Climatology”, Ph.D. Thesis (under evaluation), University of Bologna, Italy, pp. (19-35. of pages)</p>

scholarly journals In Situ–Based Reanalysis of the Global Ocean Temperature and Salinity with ISAS: Variability of the Heat Content and Steric Height

2016 ◽  
Vol 29 (4) ◽  
pp. 1305-1323 ◽  
Author(s):  
Fabienne Gaillard ◽  
Thierry Reynaud ◽  
Virginie Thierry ◽  
Nicolas Kolodziejczyk ◽  
Karina von Schuckmann
Keyword(s):  
Southern Ocean ◽  
World Ocean ◽  
Heat Content ◽  
Absolute Error ◽  
Ocean Heat Content ◽  
Global Ocean ◽  
Analysis Tool ◽  
Steric Height ◽  
The Impact

Abstract The In Situ Analysis System (ISAS) was developed to produce gridded fields of temperature and salinity that preserve as much as possible the time and space sampling capabilities of the Argo network of profiling floats. Since the first global reanalysis performed in 2009, the system has evolved, and a careful delayed-mode processing of the 2002–12 dataset has been carried out using version 6 of ISAS and updating the statistics to produce the ISAS13 analysis. This last version is now implemented as the operational analysis tool at the Coriolis data center. The robustness of the results with respect to the system evolution is explored through global quantities of climatological interest: the ocean heat content and the steric height. Estimates of errors consistent with the methodology are computed. This study shows that building reliable statistics on the fields is fundamental to improve the monthly estimates and to determine the absolute error bars. The new mean fields and variances deduced from the ISAS13 reanalysis and dataset show significant changes relative to the previous ISAS estimates, in particular in the Southern Ocean, justifying the iterative procedure. During the decade covered by Argo, the intermediate waters appear warmer and saltier in the North Atlantic and fresher in the Southern Ocean than in World Ocean Atlas 2005 long-term mean. At interannual scale, the impact of ENSO on the ocean heat content and steric height is observed during the 2006/07 and 2009/10 events captured by the network.

scholarly journals Reconstructing Global Chlorophyll-a Variations Using a Non-linear Statistical Approach

2020 ◽  
Vol 7 ◽  
Author(s):  
Elodie Martinez ◽  
Thomas Gorgues ◽  
Matthieu Lengaigne ◽  
Clement Fontana ◽  
Raphaëlle Sauzède ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Statistical Approach ◽  
Tropical Pacific ◽  
Satellite Observations ◽  
Global Ocean ◽  
Support Vector ◽  
Physical Parameters ◽  
Non Linear ◽  
Spatio Temporal ◽  
The Tropical Pacific

Monitoring the spatio-temporal variations of surface chlorophyll-a concentration (Chl, a proxy of phytoplankton biomass) greatly benefited from the availability of continuous and global ocean color satellite measurements from 1997 onward. These two decades of satellite observations are however still too short to provide a comprehensive description of Chl variations at decadal to multi-decadal timescales. This paper investigates the ability of a machine learning approach (a non-linear statistical approach based on Support Vector Regression, hereafter SVR) to reconstruct global spatio-temporal Chl variations from selected surface oceanic and atmospheric physical parameters. With a limited training period (13 years), we first demonstrate that Chl variability from a 32-years global physical-biogeochemical simulation can generally be skillfully reproduced with a SVR using the model surface variables as input parameters. We then apply the SVR to reconstruct satellite Chl observations using the physical predictors from the above numerical model and show that the Chl reconstructed by this SVR more accurately reproduces some aspects of observed Chl variability and trends compared to the model simulation. This SVR is able to reproduce the main modes of interannual Chl variations depicted by satellite observations in most regions, including El Niño signature in the tropical Pacific and Indian Oceans. In stark contrast with the trends simulated by the biogeochemical model, it also accurately captures spatial patterns of Chl trends estimated by satellite data, with a Chl increase in most extratropical regions and a Chl decrease in the center of the subtropical gyres, although the amplitude of these trends are underestimated by half. Results from our SVR reconstruction over the entire period (1979–2010) also suggest that the Interdecadal Pacific Oscillation drives a significant part of decadal Chl variations in both the tropical Pacific and Indian Oceans. Overall, this study demonstrates that non-linear statistical reconstructions can be complementary tools to in situ and satellite observations as well as conventional physical-biogeochemical numerical simulations to reconstruct and investigate Chl decadal variability.

scholarly journals How essential are Argo observations to constrain a global ocean data assimilation system?

2015 ◽  
Vol 12 (3) ◽  
pp. 1145-1186 ◽  
Author(s):  
V. Turpin ◽  
E. Remy ◽  
P. Y. Le Traon
Keyword(s):  
Data Assimilation ◽  
Forecast Error ◽  
Global Ocean ◽  
Altimeter Data ◽  
Western Boundary ◽  
Argo Data ◽  
Ocean Data Assimilation ◽  
In Situ Observations ◽  
The Impact

Abstract. Observing System Experiments (OSEs) are carried out over a one-year period to quantify the impact of Argo observations on the Mercator-Ocean 1/4° global ocean analysis and forecasting system. The reference simulation assimilates sea surface temperature (SST), SSALTO/DUACS altimeter data and Argo and other in situ observations from the Coriolis data center. Two other simulations are carried out where all Argo and half of Argo data sets are withheld. Assimilating Argo observations has a significant impact on analyzed and forecast temperature and salinity fields at different depths. Without Argo data assimilation, large errors occur in analyzed fields as estimated from the differences when compared with in situ observations. For example, in the 0–300 m layer RMS differences between analyzed fields and observations reach 0.25 psu and 1.25 °C in the western boundary currents and 0.1 psu and 0.75 °C in the open ocean. The impact of the Argo data in reducing observation-model forecast error is also significant from the surface down to a depth of 2000 m. Differences between independent observations and forecast fields are thus reduced by 20 % in the upper layers and by up to 40 % at a depth of 2000 m when Argo data are assimilated. At depth, the most impacted regions in the global ocean are the Mediterranean outflow and the Labrador Sea. A significant degradation can be observed when only half of the data are assimilated. All Argo observations thus matter, even with a 1/4° model resolution. The main conclusion is that the performance of global data assimilation systems is heavily dependent on the availability of Argo data.

scholarly journals Sedimentary supply of humic-like fluorescent dissolved organic matter and its implication for chemoautotrophic microbial activity in the Izu-Ogasawara Trench

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. Shigemitsu ◽  
T. Yokokawa ◽  
H. Uchida ◽  
S. Kawagucci ◽  
A. Murata
Keyword(s):  
Organic Matter ◽  
Community Structure ◽  
Dissolved Organic Matter ◽  
Oxygen Utilization ◽  
Fluorescent Dissolved Organic Matter ◽  
Vertical Distributions ◽  
The Difference ◽  
The Relationship ◽  
Apparent Oxygen Utilization

AbstractMicrobial community structure in the hadal water is reported to be different from that in the upper abyssal water. However, the mechanism governing the difference has not been fully understood. In this study, we investigate the vertical distributions of humic-like fluorescent dissolved organic matter (FDOMH), chemoautotrophic production, apparent oxygen utilization (AOU), and N* in the Izu-Ogasawara Trench. In the upper abyssal waters (< 6000 m), FDOMH has a significantly positive correlation with AOU; FDOMH deviates from the relationship and increases with depth without involving the increment of AOU in the hadal waters. This suggests that FDOMH is transferred from the sediments to the hadal waters through pore water, while the FDOMH is produced in situ in the upper abyssal waters. Chemoautotrophic production and N* increases and decreases with depth in the hadal waters, respectively. This corroborates the effluxes of dissolved substances, including dissolved organic matter and electron donors from sediments, which fuels the heterotrophic/chemoautotrophic microbial communities in the hadal waters. A simple box model analysis reveals that the funnel-like trench topography facilitates the increase in dissolved substances with depth in the hadal waters, which might contribute to the unique microbiological community structure in these waters.

scholarly journals The Indonesian Throughflow and its Impact on Biogeochemistry in the Indonesian Seas

2020 ◽  
Vol 37 (1) ◽  
Author(s):  
Edwards Taufiqurrahman ◽  
A’an J. Wahyudi ◽  
Yukio Masumoto
Keyword(s):  
Global Ocean ◽  
Physical Parameters ◽  
Indonesian Throughflow ◽  
Mixing Processes ◽  
Indonesian Seas ◽  
Marine Biogeochemistry ◽  
Strong Relation ◽  
Climate Systems ◽  
Critical Aspects

It has been widely known that the Indonesian Throughflow (ITF) is an important inter-ocean connection with unique and complex oceanographic and geographic conditions, as well as a strong relation to both regional and global ocean currents and climate systems. Many studies on characteristics, mechanisms, and impacts of the ITF have been conducted, mainly focusing on the ITF pathways, transport, water mass mixing processes, and their variability in connection with monsoons and climate systems. In this paper, we summarize some of the critical aspects related to ocean conditions within the Indonesian Seas and the Indonesian Throughflow, with the main focus on studies of marine biogeochemistry in a region affected by the ITF. Although the biogeochemical cycle is one of the key research topics that are needed to advance our ocean understanding, studies on marine biogeochemistry within the Indonesian Seas are quite limited due to less observed data compared to the physical parameters. Further studies on biogeochemistry and efforts to conduct in situ and remotely sensed observations in this region are strongly required. Here, we propose several biogeochemical observations correlated to the ITF.

Meteoroid trajectories from BRAMS data

2021 ◽  
Author(s):  
Hervé Lamy
Keyword(s):  
Time Delays ◽  
Specular Reflection ◽  
Linear Equations ◽  
Radio Interferometer ◽  
Additional Information ◽  
Sensitivity Pattern ◽  
Non Linear ◽  
Using Data ◽  
The Impact ◽  
Non Linear Equations

&lt;p&gt;BRAMS (Belgian RAdio Meteor Stations) is a Belgian radio network using forward scatter observations to detect and characterize meteoroids. A dedicated transmitter located in south of Belgium emits a CW signal with no modulation at a frequency of 49.97 MHz and with a power of 130 W. The network comprises currently 35 similar receiving stations located in Belgium and neighboring countries. They use Yagi antennas with a wide sensitivity pattern which therefore provide no information about the directivity of the meteor echoes. One of these stations is however a radio interferometer using the classical Jones configuration and is able to retrieve the direction of the meteor echoes.&lt;/p&gt;&lt;p&gt;We discuss here a general method to retrieve meteoroid trajectories based solely on time delays measured between meteor echoes recorded at multiple receiving stations. It is based on solving at least 6 non-linear equations to solve for the position of one specular reflection point (3 unknowns) and the 3 components of the speed. This method has also been described recently in Mazur et al (2020) and applied to CMOR data. However, specificities of the CMOR configuration has allowed simplifications that cannot be made with the BRAMS network. In order to maximize the number of meteoroid trajectories with at least 6 stations detecting meteor echoes, a number of additional stations geographically close to each other have been installed in the Limburg province in 2020. Another method to retrieve meteoroid trajectories using data from the radio interferometer and from 3 other stations is also presented.&lt;/p&gt;&lt;p&gt;We show preliminary results from both methods using also complementary data from the optical CAMS Benelux network.&amp;#160; The CAMS trajectories are used to select specific meteor echoes in the BRAMS data. The time delays between them are computed and used to solve the set of non-linear equations to retrieve the meteoroid trajectory and speed, which are then compared to the CAMS values. This allows us to assess the accuracy of both methods.&lt;/p&gt;&lt;p&gt;Finally we simulate the impact of using additional information, not currently available but that might become in a near future. This includes data from a monostatic system (a radar nearby our BRAMS transmitter is currently built), from a second radio interferometer (to be located in Limburg and/or near the transmitter), or the total range traveled by the radio wave if a coded CW transmitter such as in Vierinen et al (2016) is used.&lt;/p&gt;

scholarly journals An Assessment of Orthobaric Density in the Global Ocean

2005 ◽  
Vol 35 (11) ◽  
pp. 2054-2075 ◽  
Author(s):  
Trevor J. McDougall ◽  
David R. Jackett
Keyword(s):  
Southern Hemisphere ◽  
World Ocean ◽  
Ocean Basin ◽  
Ocean Modeling ◽  
Global Ocean ◽  
Potential Density ◽  
Vertical Coordinate ◽  
The World ◽  
Density Surface

Abstract Orthobaric density has recently been advanced as a new density variable for displaying ocean data and as a coordinate for ocean modeling. Here the extent to which orthobaric density surfaces are neutral is quantified and it is found that orthobaric density surfaces are less neutral in the World Ocean than are potential density surfaces referenced to 2000 dbar. Another property that is important for a vertical coordinate of a layered model is the quasi-material nature of the coordinate and it is shown that orthobaric density surfaces are significantly non-quasi-material. These limitations of orthobaric density arise because of its inability to accurately accommodate differences between water masses at fixed values of pressure and in situ density such as occur between the Northern and Southern Hemisphere portions of the World Ocean. It is shown that special forms of orthobaric density can be quite accurate if they are formed for an individual ocean basin and used only in that basin. While orthobaric density can be made to be approximately neutral in a single ocean basin, this is not possible in both the Northern and Southern Hemisphere portions of the Atlantic Ocean. While the helical nature of neutral trajectories (equivalently, the ill-defined nature of neutral surfaces) limits the neutrality of all types of density surface, the inability of orthobaric density surfaces to accurately accommodate more than one ocean basin is a much greater limitation.

scholarly journals A Global Ocean Observing System for Measuring Sea Level Atmospheric Pressure: Effects and Impacts on Numerical Weather Prediction

2017 ◽  
Vol 98 (2) ◽  
pp. 231-238 ◽  
Author(s):  
Luca Centurioni ◽  
András Horányi ◽  
Carla Cardinali ◽  
Etienne Charpentier ◽  
Rick Lumpkin
Keyword(s):  
Sea Level ◽  
Surface Pressure ◽  
Numerical Weather Prediction ◽  
Atmospheric Pressure ◽  
Weather Prediction ◽  
Global Ocean ◽  
Numerical Weather ◽  
Observation Impact ◽  
The Impact

Abstract Since 1994 the U.S. Global Drifter Program (GDP) and its international partners cooperating within the Data Buoy Cooperation Panel (DBCP) of the World Meteorological Organization (WMO) and the United Nations Education, Scientific and Cultural Organization (UNESCO) have been deploying drifters equipped with barometers primarily in the extratropical regions of the world’s oceans in support of operational weather forecasting. To date, the impact of the drifter data isolated from other sources has never been studied. This essay quantifies and discusses the effect and the impact of in situ sea level atmospheric pressure (SLP) data from the global drifter array on numerical weather prediction using observing system experiments and forecast sensitivity observation impact studies. The in situ drifter SLP observations are extremely valuable for anchoring the global surface pressure field and significantly contributing to accurate marine weather forecasts, especially in regions where no other in situ observations are available, for example, the Southern Ocean. Furthermore, the forecast sensitivity observation impact analysis indicates that the SLP drifter data are the most valuable per-observation contributor of the Global Observing System (GOS). All these results give evidence that surface pressure observations of drifting buoys are essential ingredients of the GOS and that their quantity, quality, and distribution should be preserved as much as possible in order to avoid any analysis and forecast degradations. The barometer upgrade program offered by the GDP, under which GDP-funded drifters can be equipped with partner-funded accurate air pressure sensors, is a practical example of how the DBCP collaboration is executed. Interested parties are encouraged to contact the GDP to discuss upgrade opportunities.

scholarly journals Spatial variability of nitrous oxide in the Minho and Lima estuaries (Portugal)

2017 ◽  
Vol 81 (3) ◽  
pp. 317 ◽  
Author(s):  
Célia Gonçalves ◽  
Maria José Brogueira
Keyword(s):  
Nitrous Oxide ◽  
Principal Component ◽  
N2o Emissions ◽  
Oxygen Utilization ◽  
N2o Production ◽  
Global Emission ◽  
High Concentrations ◽  
Positive Correlations ◽  
Apparent Oxygen Utilization

Nitrous oxide (N2O) is a potent long-lived greenhouse gas and estuaries represent potentially important sources of this biogas to the atmosphere. In this work, we analyse the first N2O data obtained in the Minho and Lima estuaries, and the processes and environmental factors that may regulate its production in these systems. In September 2006, N2O attained values of up to 20.0 nmol L–1 in the upper reaches of the Lima estuary and the river was, apparently, the main source of biogas to the system. In Minho N2O reached a maximum of 14.4 nmol L–1 and nitrification appeared to contribute to the enhancement of N2O. In the upper estuary, the relatively high concentrations of nitrification substrate NH4+, the positive correlations found between N2O level above atmospheric equilibrium (ΔN2O) and apparent oxygen utilization and NO2–, and the negative correlations between ΔN2O and NH4+ and pH can be interpreted as in situ N2O production through pelagic nitrification. Principal component analysis gave evidence of considerable differences between upper estuaries, particularly in terms of higher N2O in Lima and NH4+ in Minho. Surface waters of both estuaries were always N2O-supersaturated (101-227%) and estimated N2O emissions from Minho and Lima were 0.28 Mg N2O-N yr–1 and 0.96 Mg N2O-N yr–1, respectively, which represent a reduced fraction of N2O global emission from European estuaries.

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