Assimilation of Local and Global Datasets with Regional and Basin-scale Models of Ocean Circulation

1997 ◽  
Author(s):  
Paola Rizzoli
Keyword(s):  
Ocean Circulation ◽  
Basin Scale ◽  
Scale Models ◽  
Global Datasets

scholarly journals Toward a multivariate reanalysis of the North Atlantic Ocean biogeochemistry during 1998–2006 based on the assimilation of SeaWiFS chlorophyll data

Ocean Science ◽  
2013 ◽  
Vol 9 (1) ◽  
pp. 37-56 ◽  
Author(s):  
C. Fontana ◽  
P. Brasseur ◽  
J.-M. Brankart
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Ocean Color ◽  
Data Set ◽  
The North ◽  
Basin Scale ◽  
Non Linear ◽  
Color Data ◽  
The North Atlantic ◽  
Ocean Biogeochemistry

Abstract. Today, the routine assimilation of satellite data into operational models of ocean circulation is mature enough to enable the production of global reanalyses describing the ocean circulation variability during the past decades. The expansion of the "reanalysis" concept from ocean physics to biogeochemistry is a timely challenge that motivates the present study. The objective of this paper is to investigate the potential benefits of assimilating satellite-estimated chlorophyll data into a basin-scale three-dimensional coupled physical–biogeochemical model of the North Atlantic. The aim is on the one hand to improve forecasts of ocean biogeochemical properties and on the other hand to define a methodology for producing data-driven climatologies based on coupled physical–biogeochemical modeling. A simplified variant of the Kalman filter is used to assimilate ocean color data during a 9-year period. In this frame, two experiments are carried out, with and without anamorphic transformations of the state vector variables. Data assimilation efficiency is assessed with respect to the assimilated data set, nitrate of the World Ocean Atlas database and a derived climatology. Along the simulation period, the non-linear assimilation scheme clearly improves the surface analysis and forecast chlorophyll concentrations, especially in the North Atlantic bloom region. Nitrate concentration forecasts are also improved thanks to the assimilation of ocean color data while this improvement is limited to the upper layer of the water column, in agreement with recent related literature. This feature is explained by the weak correlation taken into account by the assimilation between surface phytoplankton and nitrate concentrations deeper than 50 meters. The assessment of the non-linear assimilation experiments indicates that the proposed methodology provides the skeleton of an assimilative system suitable for reanalyzing the ocean biogeochemistry based on ocean color data.

scholarly journals A synthesis of marine sediment core δ<sup>13</sup>C data over the last 150 000 years

2010 ◽  
Vol 6 (5) ◽  
pp. 645-673 ◽  
Author(s):  
K. I. C. Oliver ◽  
B. A. A. Hoogakker ◽  
S. Crowhurst ◽  
G. M. Henderson ◽  
R. E. M. Rickaby ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Carbon Storage ◽  
Ocean Circulation ◽  
Marine Sediment ◽  
Large Scale ◽  
Dissolved Inorganic Carbon ◽  
Deep Ocean ◽  
Global Ocean ◽  
Last Interglacial ◽  
Basin Scale

Abstract. The isotopic composition of carbon, δ13C, in seawater is used in reconstructions of ocean circulation, marine productivity, air-sea gas exchange, and biosphere carbon storage. Here, a synthesis of δ13C measurements taken from foraminifera in marine sediment cores over the last 150 000 years is presented. The dataset comprises previously published and unpublished data from benthic and planktonic records throughout the global ocean. Data are placed on a common δ18O age scale suitable for examining orbital timescale variability but not millennial events, which are removed by a 10 ka filter. Error estimates account for the resolution and scatter of the original data, and uncertainty in the relationship between δ13C of calcite and of dissolved inorganic carbon (DIC) in seawater. This will assist comparison with δ13C of DIC output from models, which can be further improved using model outputs such as temperature, DIC concentration, and alkalinity to improve estimates of fractionation during calcite formation. High global deep ocean δ13C, indicating isotopically heavy carbon, is obtained during Marine Isotope Stages (MIS) 1, 3, 5a, c and e, and low δ13C during MIS 2, 4 and 6, which are temperature minima, with larger amplitude variability in the Atlantic Ocean than the Pacific Ocean. This is likely to result from changes in biosphere carbon storage, modulated by changes in ocean circulation, productivity, and air-sea gas exchange. The North Atlantic vertical δ13C gradient is greater during temperature minima than temperature maxima, attributed to changes in the spatial extent of Atlantic source waters. There are insufficient data from shallower than 2500 m to obtain a coherent pattern in other ocean basins. The data synthesis indicates that basin-scale δ13C during the last interglacial (MIS 5e) is not clearly distinguishable from the Holocene (MIS 1) or from MIS 5a and 5c, despite significant differences in ice volume and atmospheric CO2 concentration during these intervals. Similarly, MIS 6 is only distinguishable from MIS 2 or 4 due to globally lower δ13C values both in benthic and planktonic data. This result is obtained despite individual records showing differences between these intervals, indicating that care must be used in interpreting large scale signals from a small number of records.

Ocean Circulation from the synergy of altimeter-derived and oceanic tracers observations

2021 ◽  
Author(s):  
Daniele Ciani ◽  
Marie-Hélène Rio ◽  
Bruno Buongiorno Nardelli ◽  
Stéphanie Guinehut ◽  
Elodie Charles ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Time Window ◽  
Ocean Surface ◽  
Global Scale ◽  
Surface Currents ◽  
Sensitivity Experiment ◽  
Daily Data ◽  
Basin Scale ◽  
Ocean Surface Currents ◽  
Spatio Temporal

&lt;p&gt;Measuring the ocean surface currents at high spatio-temporal resolutions is crucial for scientific and socio-economic applications. Since the early 1990s, the synoptic and global-scale monitoring of the ocean surface currents has been provided by constellations of Radar Altimeters. The Altimeter observations enable to derive the geostrophic component of the surface currents with effective spatial-temporal resolutions O(100 km) and O(10 days), respectively. Therefore, only the largest mesoscale oceanic features can be accurately resolved. In order to enhance the altimeter system capabilities, we propose a synergistic use of high resolution, satellite-derived Sea Surface Temperature (SST), Chlorophyll concentrations (Chl) and Altimeter-derived currents. Our approach is tested in both global-scale and regional contexts.&lt;br&gt;At global scale, relying on past numerical studies, we perform a sensitivity experiment based on several gap-free SST datasets, emphasizing strengths and weaknesses in ocean currents applications. Overall, the comparison with in-situ measured currents shows that our synergistic method can improve the altimeter estimates up to 30% locally.&lt;br&gt;Then, our method is also implemented with Chl data in the&amp;#160; Mediterranean Sea, where the most energetic variable signals are found at spatio-temporal scales up to 10 km and few days. We test the method feasibility in an Observing System Simulation Experiment relying on model outputs of the European Copernicus Marine Service. Statistical analyses based on the 2017 daily data show that our approach can improve the altimeter-derived currents accuracy up to 50% at the basin scale, also enhancing the effective spatial-temporal resolutions up to 30 km and less than 10 days, respectively. The method efficiency decreases when the surface Chl patterns are dominated by the biological activity rather than the currents advection, which mostly occurs in the mid-February to mid-March time window. Preliminary tests on the method applicability to satellite-derived data are also presented and discussed.&lt;/p&gt;

scholarly journals Finding the ‘lost years’ in green turtles: insights from ocean circulation models and genetic analysis

2013 ◽  
Vol 280 (1768) ◽  
pp. 20131468 ◽  
Author(s):  
Nathan F. Putman ◽  
Eugenia Naro-Maciel
Keyword(s):  
Genetic Analysis ◽  
Ocean Circulation ◽  
Circulation Model ◽  
Chelonia Mydas ◽  
Ecological Processes ◽  
Green Turtles ◽  
New Information ◽  
Basin Scale ◽  
Conservation Concern ◽  
Critical Developmental Period

Organismal movement is an essential component of ecological processes and connectivity among ecosystems. However, estimating connectivity and identifying corridors of movement are challenging in oceanic organisms such as young turtles that disperse into the open sea and remain largely unobserved during a period known as ‘the lost years’. Using predictions of transport within an ocean circulation model and data from published genetic analysis, we present to our knowledge, the first basin-scale hypothesis of distribution and connectivity among major rookeries and foraging grounds (FGs) of green turtles ( Chelonia mydas ) during their ‘lost years’. Simulations indicate that transatlantic dispersal is likely to be common and that recurrent connectivity between the southwestern Indian Ocean and the South Atlantic is possible. The predicted distribution of pelagic juvenile turtles suggests that many ‘lost years hotspots’ are presently unstudied and located outside protected areas. These models, therefore, provide new information on possible dispersal pathways that link nesting beaches with FGs. These pathways may be of exceptional conservation concern owing to their importance for sea turtles during a critical developmental period.

scholarly journals Effects of mesoscale eddies on behavior of an oil spill resulting from an accidental deepwater blowout in the Black Sea: an assessment of the environmental impacts

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5448
Author(s):  
Konstantin A. Korotenko
Keyword(s):  
Black Sea ◽  
Oil Spill ◽  
Marine Environment ◽  
Ocean Circulation ◽  
Coupled Model ◽  
Circulation Model ◽  
The Black Sea ◽  
Basin Scale ◽  
Near Shore ◽  
Oil Source

Because of the environmental sensitivity of the Black Sea, as a semi-enclosed sea, any subsea oil spill can cause destructive impacts on the marine environment and beaches. Employing numerical modeling as a prediction tool is one of the most efficient methods to understand oil spill behavior under various environmental forces. In this regard, a coupled circulation/deepsea oil spill model has been applied to the Black Sea to address the behavior of the oil plume resulting from a representative hypothetical deepwater blowout. With climatological forcing, the hydrodynamic module based on DieCAST ocean circulation model realistically reproduces seasonally-varying circulation from basin-scale dominant structures to meso- and sub-mesoscale elements. The oil spill model utilizes pre-calculated DieCAST thermo-hydrodynamic fields and uses a Lagrangian tracking algorithm for predicting the displacement of a large number of seeded oil droplets, the sum of which forms the rising oil plume resulting from a deepwater blowout. Basic processes affecting the transport, dispersal of oil and its fate in the water column are included in the coupled model. A hypothetical oil source was set at the bottom, at the northwestern edge of the Shatsky Ridge in the area east of the Crimea Peninsula where the oil exploration/development is likely to be planned. Goals of the study are to elucidate the behavior of the subsea oil plume and assess scales of contamination of marine environment and coastlines resulting from potential blowouts. The two 20-day scenarios with the oil released by a hypothetical blowout were examined to reveal combined effects of the basin-scale current, near-shore eddies, and winds on the behavior of the rising oil plume and its spreading on the surface. Special attention is paid to the Caucasian near-shore anticyclonic eddy which is able to trap surfacing oil, detain it and deliver it to shores. The length of contaminated coastlines of vulnerable Crimean and Caucasian coasts are assessed along with amounts of oil beached and deposited.

scholarly journals Decadal acidification in the water masses of the Atlantic Ocean

2015 ◽  
Vol 112 (32) ◽  
pp. 9950-9955 ◽  
Author(s):  
Aida F. Ríos ◽  
Laure Resplandy ◽  
Maribel I. García-Ibáñez ◽  
Noelia M. Fajar ◽  
Anton Velo ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Ocean Circulation ◽  
Climate Model ◽  
Southern Annular Mode ◽  
South Atlantic ◽  
Water Masses ◽  
Global Ocean ◽  
Ph Change ◽  
Basin Scale ◽  
Intermediate Waters

Global ocean acidification is caused primarily by the ocean’s uptake of CO2 as a consequence of increasing atmospheric CO2 levels. We present observations of the oceanic decrease in pH at the basin scale (50°S–36°N) for the Atlantic Ocean over two decades (1993–2013). Changes in pH associated with the uptake of anthropogenic CO2 (ΔpHCant) and with variations caused by biological activity and ocean circulation (ΔpHNat) are evaluated for different water masses. Output from an Institut Pierre Simon Laplace climate model is used to place the results into a longer-term perspective and to elucidate the mechanisms responsible for pH change. The largest decreases in pH (∆pH) were observed in central, mode, and intermediate waters, with a maximum ΔpH value in South Atlantic Central Waters of −0.042 ± 0.003. The ΔpH trended toward zero in deep and bottom waters. Observations and model results show that pH changes generally are dominated by the anthropogenic component, which accounts for rates between −0.0015 and −0.0020/y in the central waters. The anthropogenic and natural components are of the same order of magnitude and reinforce one another in mode and intermediate waters over the time period. Large negative ΔpHNat values observed in mode and intermediate waters are driven primarily by changes in CO2 content and are consistent with (i) a poleward shift of the formation region during the positive phase of the Southern Annular Mode in the South Atlantic and (ii) an increase in the rate of the water mass formation in the North Atlantic.

scholarly journals Ocean state estimations for synthesis of ocean-mixing observations

2021 ◽  
Author(s):  
Shuhei Masuda ◽  
Satoshi Osafune
Keyword(s):  
State Estimation ◽  
Ocean Circulation ◽  
Numerical Models ◽  
Vertical Mixing ◽  
Global Ocean ◽  
Current Status ◽  
Observation Data ◽  
Ocean Mixing ◽  
Basin Scale ◽  
State Estimations

AbstractVertical mixing in oceans is an essential component of the dynamics of ocean circulation, including meridional circulation. Nevertheless, various aspects of mixing, particularly in conjunction with global ocean energetics, remain debatable. One of the biggest reasons is the lack of observational facts. With the recent expansion of global vertical-mixing observations, attempts have been made to estimate the ocean state using vertical-mixing observation data to better understand the role of mixing in oceanography. In this review, we discuss the current status of the ocean state estimation and future synthesis of vertically mixing observation data into the oceanic basin-scale state estimation, including progress of data assimilation studies using numerical models. These will contribute to the construction of the future line of observation, model, and data synthesis studies along which the issues on ocean mixing can be consistently resolved.

Variability of the southwest Indian Ocean

2005 ◽  
Vol 363 (1826) ◽  
pp. 63-76 ◽  
Author(s):  
Wilhelmus P. M. de Ruijter ◽  
Herman Ridderinkhof ◽  
Mathijs W. Schouten
Keyword(s):  
Indian Ocean ◽  
Ocean Circulation ◽  
Global Scale ◽  
Equatorial Region ◽  
Meridional Overturning Circulation ◽  
Central Basin ◽  
Southwest Indian Ocean ◽  
Basin Scale ◽  
Meridional Overturning ◽  
The Indian Ocean

The variability in the southwest Indian Ocean is connected to the basin–scale and global–scale ocean circulation. Two bands of enhanced variability stretch across the Southern Indian Ocean east of Madagascar around 12○ S and 25○ S, respectively. They mark the preferred routes along which anomalies, generated by varying forcing over the central basin, near the eastern boundary or in the equatorial region, propagate westward as baroclinic Rossby waves. Sea–surface height anomalies pass along the northern tip of Madagascar and are observed by satellite altimetry to propagate into the central Mozambique Channel. There, eddies are subsequently formed that propagate southward into the Agulhas retroflection region. The anomalies along the southern band trigger the formation of large dipolar vortex pairs in the separation region of the East Madagascar Current at the southern tip of the island. South of Africa these eddies and dipoles trigger the shedding of Agulhas Rings that feed the Atlantic meridional overturning circulation with warm, salty, Indian Ocean water. Interannual variability of the forcing over the Indian Ocean, such as that associated with the Indian Ocean Dipole/El Niño climate modes, propagates along these pathways and leads to associated modulations of the eddy transports into the South Atlantic.

scholarly journals A synthesis of marine sediment core δ<sup>13</sup>C data over the last 150 000 years

2009 ◽  
Vol 5 (6) ◽  
pp. 2497-2554 ◽  
Author(s):  
K. I. C. Oliver ◽  
B. A. A. Hoogakker ◽  
S. Crowhurst ◽  
G. M. Henderson ◽  
R. E. M. Rickaby ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Carbon Storage ◽  
Ocean Circulation ◽  
Marine Sediment ◽  
Large Scale ◽  
Dissolved Inorganic Carbon ◽  
Deep Ocean ◽  
Global Ocean ◽  
Last Interglacial ◽  
Basin Scale

Abstract. The isotopic composition of carbon, δ13C, in seawater is used in reconstructions of ocean circulation, marine productivity, air-sea gas exchange, and biosphere carbon storage. Here, a synthesis of δ13C measurements taken from foraminifera in marine sediment cores over the last 150 000 years is presented. The dataset comprises previously published and unpublished data from benthic and planktonic records throughout the global ocean. Data are placed on a common δ18O age scale and filtered to remove timescales shorter than 6 kyr. Error estimates account for the resolution and scatter of the original data, and uncertainty in the relationship between δ13C of calcite and of dissolved inorganic carbon (DIC) in seawater. This will assist comparison with δ13C of DIC output from models, which can be further improved using model outputs such as temperature, DIC concentration, and alkalinity to improve estimates of fractionation during calcite formation. High global deep ocean δ13C, indicating isotopically heavy carbon, is obtained during Marine Isotope Stages (MIS) 1, 3, 5a, 5c and 5e, and low δ13C during MIS 2, 4 and 6, which are temperature minima, with larger amplitude variability in the Atlantic Ocean than the Pacific Ocean. This is likely to result from changes in biosphere carbon storage, modulated by changes in ocean circulation, productivity, and air-sea gas exchange. The North Atlantic vertical δ13C gradient is greater during temperature minima than temperature maxima, attributed to changes in the spatial extent of Atlantic source waters. There are insufficient data from shallower than 2500 m to obtain a coherent pattern in other ocean basins. The data synthesis indicates that basin-scale δ13C during the last interglacial (MIS 5e) is not clearly distinguishable from the Holocene (MIS 1) or from MIS 5a and 5c, despite significant differences in ice volume and atmospheric CO2 concentration during these intervals. Similarly, MIS 6 is only distinguishable from MIS 2 or 4 due to globally lower δ13C values both in benthic and planktonic data. This result is obtained despite individual records showing differences between these intervals, indicating that care must be used in interpreting large scale signals from a small number of records.

scholarly journals The role of vertical shear on the horizontal oceanic dispersion

2015 ◽  
Vol 12 (5) ◽  
pp. 2073-2096
Author(s):  
A. S. Lanotte ◽  
R. Corrado ◽  
G. Lacorata ◽  
L. Palatella ◽  
C. Pizzigalli ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Vertical Velocity ◽  
Marine Biology ◽  
Pollutant Dispersion ◽  
Ocean Model ◽  
Three Dimensions ◽  
Vertical Shear ◽  
Time Variability ◽  
Horizontal Dispersion ◽  
Basin Scale

Abstract. The effect of vertical shear on the horizontal dispersion properties of passive tracer particles on the continental shelf of South Mediterranean is investigated by means of observative and model data. In-situ current measurements reveal that vertical velocity gradients in the upper mixed layer decorrelate quite fast (∼ 1 day), whereas basin-scale ocean circulation models tend to overestimate such decorrelation time because of finite resolution effects. Horizontal dispersion simulated by an eddy-permitting ocean model, like, e.g., the Mediterranean Forecasting System, is mosty affected by: (1) unresolved scale motions, and mesoscale motions that are largely smoothed out; (2) poorly resolved time variability of vertical velocity profiles in the upper layer. For the case study we have analysed, we show that a suitable use of kinematic parameterisations is helpful to implement realistic statistical features of tracer dispersion in two and three dimensions. The approach here suggested provides a functional tool to control the horizontal spreading of small organisms or substance concentrations, and is thus relevant for marine biology, pollutant dispersion as well as oil spill applications.

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