annalisa bracco - Academia.edu (original) (raw)
Papers by annalisa bracco
Climate dynamics, Feb 7, 2024
This study investigates the representation of ocean convection in the Labrador Sea in seven Earth... more This study investigates the representation of ocean convection in the Labrador Sea in seven Earth System Models (ESMs) from the Coupled Model Intercomparison Project Phase 5 and 6 datasets. The relative role of the oceanic and atmospheric biases in the subpolar North Atlantic gyre are explored using regional ocean simulations where the atmospheric forcing or the ocean initial and boundary conditions are replaced by reanalysis data in the absence of interactive air-sea coupling. Commonalities and differences among model behaviors are discussed with the objective of finding a pathway forward to improve the representation of the ocean mean state and variability in a region of fundamental importance for climate variability and change. Results highlight that an improved representation of ocean stratification in the North Atlantic subpolar gyre is urgently needed to constrain future climate change projections. While improving the ocean model resolution in the North Atlantic alone may contribute a better representation of both boundary currents and propagation of heat and freshwater anomalies into the Labrador Sea, it may not be sufficient. Addressing the atmospheric heat flux bias with better resolution in the atmosphere and land topography may allow for deep convection to occur in the Labrador Sea in some of the models that miss it entirely, but the greatest priority remains improving the representation of ocean stratification.
AGU Fall Meeting Abstracts, Dec 1, 2010
ABSTRACT Positively buoyant organisms such as the macroalgae Sargassum and the cyanobacteria Tric... more ABSTRACT Positively buoyant organisms such as the macroalgae Sargassum and the cyanobacteria Trichodesmiumm often form surface accumulations visible in satellite imagery. Here we discuss the accumulation of floating material in the ocean in presence of meso- and submesoscales activity. Using high resolution simulations of the ocean mesoscale in both idealized and realistic domains (specifically in a 3D box where coherent eddies are forced by small-scale winds, and in the western Gulf of Mexico, where extensive concentrations of floating Sargassum have been recorded in satellite images) we show that the distribution of tracers at ocean surface departs rapidly from the one observed few tens of meters below it. Such distribution does not resemble what observed for passive tracers in quasigeostrophic turbulence. The strong divergence and convergence zones generated at the surface by the eddy field are responsible for the creation of `lines' where the floating material accumulates. Floating particles are expelled from the core of the eddies, and concentrate in convergence regions of size and strength comparable to the ones observed through the satellite images. In light of those results, Sargassum and/or Trichodesmium may provide a useful proxy to track convergence/divergence processes at the ocean surface.
Progress in Oceanography, Mar 1, 2023
Journal Of Geophysical Research: Oceans, May 6, 2022
• LCS and MARS show two-way interaction related with river representation and resolution. • Sprea... more • LCS and MARS show two-way interaction related with river representation and resolution. • Spread of SST and SSS show strong, but opposite, seasonalities. • Increasing resolution decreases the predictability of surface relative vorticity.
published before the data being registered and available, such that the persistent identifier res... more published before the data being registered and available, such that the persistent identifier resolves. These repositories are known, community-accepted repositories, and acceptable for use. Authors must still provide preliminary access to reviewers at the time of submission. Please ensure that your data and software are available with details of the online access location(s), data product names, variable names, time ranges, spatial locations, or any other search criteria to allow a reader and reviewer to Find and Access the data used and/or generated for the paper (including those represented in figures and tables). In summary, any data and software utilized in the work contained in the manuscript must be documented for free and open availability. Data or software that are sensitive and require restrictions on access (e.g., personal data, medical information, fossil locations, strategic models) must be preserved in a repository with appropriate access controls. 2. Availability Statement in Open Research Section (required) a. Data Availability Statement (required): A Data Availability Statement is required in the Open Research section of your paper describing where and how your data are available, including an online means to access your data. Check links and files before submitting your paper to the journal so as to ensure the data are accessible for peer review. Many data repositories provide confidential data access for this purpose. For data that are not publicly available, sensitive, or restricted, examples, templates, and specific guidance are provided in this document. b. Software Availability Statement (required): A Software Availability Statement is required in the Open Research section of your paper for software that is central to your research such as for model simulations, data analysis, data visualization, and model output analysis. The Availability Statement should contain a citation, licensing information, access restrictions, and a link to the development platform (e.g. GitHub). Note that "git/GitHub/GitLab" are not acceptable software repositories because they are not archival. For software that are not publicly available, sensitive, or restricted, examples, templates, and specific guidance, are provided in this document.
Bulletin of the American Physical Society, Mar 6, 2018
Proceedings, May 1, 2021
As a marginal sea connected to neighboring basins through straits, the Gulf of Mexico (GoM) is dy... more As a marginal sea connected to neighboring basins through straits, the Gulf of Mexico (GoM) is dynamically and topographically complex. Physical processes are strongly influenced by the interaction of circulation in the GoM deep basin interior and in the surrounding shelf areas of diverse morphologies that include deltas, estuaries, barrier islands and marshes. This was particularly evident during the 2010 Deepwater Horizon (DwH) incident, a deep blow-out close to the Northern GoM shelves, over an area strongly affected by the brackish river plume originated from the Mississippi River Delta. The specific physical conditions are revisited, to illustrate the synergy between the evolution of the Loop Current-Florida Current system and the rapidly changing shelf and coastal currents under the influence of river runoff and winds. Each of these physical factors had been studied prior to the DwH incident, but their combined effects on hydrocarbon pathways were not known. Examples are given on what has been learned through research under the Gulf of Mexico Research Initiative (GoMRI) in the last 10 years. The focus is on transport processes in the GoM along the ocean continuum from the deep basin interior to the coastal and
Journal of the Acoustical Society of America, Oct 1, 2022
Accurate numerical simulations of underwater acoustic propagation in a dynamic ocean—and its asso... more Accurate numerical simulations of underwater acoustic propagation in a dynamic ocean—and its associated uncertainty—require using realistic environmental parameters as inputs and especially a high-fidelity representation of the expected spatio-temporal variability of the ocean sound speed in the volume of interest. In areas characterized by strong temperature and salinity variations (e.g., associated with long-living mesoscale eddies in the Gulf of Mexico), the approximate simulation of the 3D sound-speed field and its variability requires predictive oceanographic models capable of resolving such variations. This study investigates the impact of vertical resolution focusing on how it shapes the representation of the 3D sound speed variability through a suite of simulations of the northern Gulf of Mexico performed with a regional ocean model run at submesoscale permitting horizontal resolution (0.5 km) using increasing vertical resolution from 30 to 200 terrain-following layers over a one-month simulation interval (as described in the companion paper presented by Touret et al.). Geo-acoustic parameters were matched to the existing sediment database. In selected areas influenced by mesoscale eddies, ray tracing is used to determine the significance of increased resolution on acoustic propagation as a function of the sensor configurations and the expected sound speed variability.
Journal of the Acoustical Society of America, Oct 1, 2022
Vertical resolution affects the representation of ocean sound speed according to a suite of regio... more Vertical resolution affects the representation of ocean sound speed according to a suite of regional simulations of the De Soto Canyon circulation in the Gulf of Mexico. Simulations have identical horizontal resolution of 0.5 km, partially resolving submesoscale dynamics, and increasing vertical resolution from 30 (i.e., comparable to what commonly used in mesoscale permitting or resolving hindcast and forecast products such as HYCOM) to 200 terrain-following layers. Simulations with 30- and 70-layers underestimate the ageostrophic contributions in and around the eddies below the mixed-layer and do not reproduce the sharp vorticity and density variations associated with the mesoscale circulations compared to the 140- and 200-layers runs. The ocean sound speed (based on the classical MacKenzie formula) was found to be far more variable when the submesoscale, ageostrophic circulations are captured also in their vertical structure and vertical contributions to the density field. Hence, the results of this study indicate that to better predict the influence of the submesocale oceanic circulation on ocean sound speed variability, model simulations should consider enhancing both horizontal and vertical resolution to resolve at least the first 3 baroclinic modes. To do so, more than 100 vertical layers were found to be needed in this study.
Authorea (Authorea), Mar 26, 2023
Diatoms are among the most efficient marine organisms for primary production and carbon sequestra... more Diatoms are among the most efficient marine organisms for primary production and carbon sequestration, absorbing at least 10 billion tonnes of carbon dioxide every year. Yet, the spatial distributions of these planktonic organisms remain puzzling and the underlying physical processes poorly known. Here we investigate what dynamical conditions are conductive to episodic diatom blooms in oligotrophic waters based on Lagrangian diagnosis and satellite-derived phytoplankton functional types and ocean currents. The Lagrangian coherence of the flow is diagnosed in space and time simultaneously to identify which structures favor diatom growth. Observations evidence that flow structures with a high degree of coherence (40 days or longer) in high turbulent kinetic energy and vorticity sustain high concentrations of diatoms in the sunlite layers. Our findings show that the integration of Eulerian kinematic variables into a Lagrangian frame allows revealing new dynamical aspects of geophysical turbulence and unveil transport properties having large biological impacts.
arXiv (Cornell University), Oct 7, 2021
The threat of global warming and the demand for reliable climate predictions pose a formidable ch... more The threat of global warming and the demand for reliable climate predictions pose a formidable challenge being the climate system multiscale, high-dimensional and nonlinear. Spatiotemporal recurrences of the system hint to the presence of a low-dimensional manifold containing the highdimensional climate trajectory that could make the problem more tractable. Here we argue that reproducing the geometrical and topological properties of the low-dimensional attractor should be a key target for models used in climate projections. In doing so, we propose a general data-driven framework to characterize the climate attractor and showcase it in the tropical Pacific ocean using a reanalysis as observational proxy and two state-of-the-art models. The analysis spans four variables simultaneously over the periods 1979-2019 and 2060-2100. At each time t, the system can be uniquely described by a state space vector parameterized by N variables and their spatial variability. The dynamics is confined on a manifold with dimension lower than the full state space that we characterize through manifold learning algorithms, both linear and nonlinear. Nonlinear algorithms describe the attractor through fewer components than linear ones by considering its curved geometry, allowing for visualizing the high-dimensional dynamics through low-dimensional projections. The local geometry and local stability of the high-dimensional, multi-variable climate attractor are quantified through the local dimension and persistence metrics. Model biases that hamper climate predictability are identified and found to be similar in the multivariate attractor of the two models during the historical period while diverging under the warming scenario considered. Finally, the relationships between different sub-spaces (univariate fields), and therefore among climate variables, are evaluated. The proposed framework provides a comprehensive, physically based, test for assessing climate feedbacks and opens new avenues for improving their model representation.
Frontiers in Marine Science, Dec 10, 2021
Fine-scale larval dispersal and connectivity processes are key to species survival, growth, recov... more Fine-scale larval dispersal and connectivity processes are key to species survival, growth, recovery and adaptation under rapidly changing disturbances. Quantifying both are required to develop any effective management strategy. In the present work, we examine the dispersal pattern and potential connectivity of a common deepwater coral, Paramuricea biscaya, found in the northern Gulf of Mexico by evaluating predictions of physical models with estimates of genetic connectivity. While genetic approaches provide estimates of realized connectivity, they do not provide information on the dispersal process. Physical circulation models can now achieve kilometerscale resolution sufficient to provide detailed insight into the pathways and scales of larval dispersal. A high-resolution regional ocean circulation model is integrated for 2015 and its advective pathways are compared with the outcome of the genetic connectivity estimates of corals collected at six locations over the continental slope at depths comprised between 1,000 and 3,000 m. Furthermore, the likely interannual variability is extrapolated using ocean hindcasts available for this basin. The general connectivity pattern exhibits a dispersal trend from east to west following 1,000 to 2,000-m isobaths, corresponding to the overall westward near-bottom circulation. The connectivity networks predicted by our model were mostly congruent with the estimated genetic connectivity patterns. Our results show that although dispersal distances of 100 km or less are common, depth differences between tens to a few hundred meters can effectively limit larval dispersal. A probabilistic graphic model suggests that stepping-stone dispersal mediated by intermediate sites provides a likely mechanism for long-distance connectivity between the populations separated by distances of 300 km or greater, such as those found in the DeSoto and Keathley canyons.
Climate Dynamics, Nov 15, 2022
Earth’s Future, Nov 1, 2018
During recent decades, through theoretical considerations and analyses of observations and model ... more During recent decades, through theoretical considerations and analyses of observations and model simulations, the scientific community has fundamentally advanced our understanding of the coupled climate system, thereby establishing that humans affect the Earth's climate. Resulting from this remarkable accomplishment, the COP21 agreement marks a historic turning point for climate research by calling for actionable regional climate change information on time scales from seasonal to centuries for the benefit of humanity, as well as living and nonliving elements of the Earth environment. Out of the underlying United National Framework Convention on climate Change process, improving seamless regional climate forecast capabilities emerges as a key challenge for the international research community. Addressing it requires a multiscale approach to climate predictions. Here we offer a vision that emphasizes enhanced scientific understanding of regional to local climate processes as the foundation for progress. The scientific challenge is extreme due to the rich complexity of interactions and feedbacks between regional and global processes, each of which affects the global climate trajectory. To gain the necessary scientific insight and to turn it into actionable climate information require technical development, international coordination, and a close interaction between the science and stakeholder communities. Plain Language Summary During recent decades, through theoretical considerations and analyses of observations and model simulations, the scientific community has fundamentally advanced our understanding of the coupled climate system, thereby establishing that humans affect the Earth's climate. Building on this remarkable accomplishment, the COP21 agreement marks a historic turning point for climate research by calling for actionable regional climate change information on time scales from seasonal to centuries for the benefit of humanity and the full biosphere. Out of the underlying United National Framework Convention on climate Change process, improving seamless regional climate forecast capabilities emerges as a closely linked challenge for the international research community. Addressing this challenge requires a multiscale approach to climate predictions. Here we offer a vision for realizing an approach that emphasizes enhanced scientific understanding of regional to local climate processes as the foundation for progress. The scientific challenge is extreme due to the rich complexity of interactions and feedbacks between regional and global processes, each of which affects the global climate trajectory. Technical development, international coordination, and a close interaction between the science and stakeholder communities are also required. In their absence scientific insight cannot be gained or turned into actionable climate information.
Journal Of Geophysical Research: Oceans, Jun 1, 2019
Coastal waters in the Labrador Sea are influenced by the seasonal input of meltwater from the Gre... more Coastal waters in the Labrador Sea are influenced by the seasonal input of meltwater from the Greenland ice sheet, which is predicted to more than double by the end of the century. Mechanisms controlling the offshore export of meltwater can have a significant effect on stratification and vertical stability in the Labrador Sea, being particularly important if the meltwater is transported toward the interior of the basin where winter convection occurs. Here we use a high-resolution ocean model to show that coastal upwelling winds play a critical role transporting the meltwater offshore to about 150 km from the coast, where increased eddy activity and mean circulation can then transport the meltwater farther offshore. While meltwater discharged from West Greenland is either transported to Baffin Bay or circumnavigates the basin flowing mostly along isobaths, meltwater from East Greenland can reach the interior of the basin where it may influence stratification and winter convection whenever winds are anomalously upwelling favorable in late summer and early fall. Plain Language Summary Every summer, coastal waters off Greenland are influenced by the input of freshwater from ice sheet melting. Based on analyses of ocean model simulations, we show that meltwater transport in the Labrador Sea is controlled by multiple processes. Winds play an important role, transporting the freshwater to about 150 km from the coast, where the large-scale circulation and eddies can transport the meltwater farther offshore. Most of the meltwater is transported either northward into Baffin Bay or around the basin. When winds are anomalously upwelling favorable in late summer or early fall, however, meltwater from East Greenland can be transported into the interior of the basin where it may influence vertical stratification and winter convection.
Climate dynamics, Feb 7, 2024
This study investigates the representation of ocean convection in the Labrador Sea in seven Earth... more This study investigates the representation of ocean convection in the Labrador Sea in seven Earth System Models (ESMs) from the Coupled Model Intercomparison Project Phase 5 and 6 datasets. The relative role of the oceanic and atmospheric biases in the subpolar North Atlantic gyre are explored using regional ocean simulations where the atmospheric forcing or the ocean initial and boundary conditions are replaced by reanalysis data in the absence of interactive air-sea coupling. Commonalities and differences among model behaviors are discussed with the objective of finding a pathway forward to improve the representation of the ocean mean state and variability in a region of fundamental importance for climate variability and change. Results highlight that an improved representation of ocean stratification in the North Atlantic subpolar gyre is urgently needed to constrain future climate change projections. While improving the ocean model resolution in the North Atlantic alone may contribute a better representation of both boundary currents and propagation of heat and freshwater anomalies into the Labrador Sea, it may not be sufficient. Addressing the atmospheric heat flux bias with better resolution in the atmosphere and land topography may allow for deep convection to occur in the Labrador Sea in some of the models that miss it entirely, but the greatest priority remains improving the representation of ocean stratification.
AGU Fall Meeting Abstracts, Dec 1, 2010
ABSTRACT Positively buoyant organisms such as the macroalgae Sargassum and the cyanobacteria Tric... more ABSTRACT Positively buoyant organisms such as the macroalgae Sargassum and the cyanobacteria Trichodesmiumm often form surface accumulations visible in satellite imagery. Here we discuss the accumulation of floating material in the ocean in presence of meso- and submesoscales activity. Using high resolution simulations of the ocean mesoscale in both idealized and realistic domains (specifically in a 3D box where coherent eddies are forced by small-scale winds, and in the western Gulf of Mexico, where extensive concentrations of floating Sargassum have been recorded in satellite images) we show that the distribution of tracers at ocean surface departs rapidly from the one observed few tens of meters below it. Such distribution does not resemble what observed for passive tracers in quasigeostrophic turbulence. The strong divergence and convergence zones generated at the surface by the eddy field are responsible for the creation of `lines' where the floating material accumulates. Floating particles are expelled from the core of the eddies, and concentrate in convergence regions of size and strength comparable to the ones observed through the satellite images. In light of those results, Sargassum and/or Trichodesmium may provide a useful proxy to track convergence/divergence processes at the ocean surface.
Progress in Oceanography, Mar 1, 2023
Journal Of Geophysical Research: Oceans, May 6, 2022
• LCS and MARS show two-way interaction related with river representation and resolution. • Sprea... more • LCS and MARS show two-way interaction related with river representation and resolution. • Spread of SST and SSS show strong, but opposite, seasonalities. • Increasing resolution decreases the predictability of surface relative vorticity.
published before the data being registered and available, such that the persistent identifier res... more published before the data being registered and available, such that the persistent identifier resolves. These repositories are known, community-accepted repositories, and acceptable for use. Authors must still provide preliminary access to reviewers at the time of submission. Please ensure that your data and software are available with details of the online access location(s), data product names, variable names, time ranges, spatial locations, or any other search criteria to allow a reader and reviewer to Find and Access the data used and/or generated for the paper (including those represented in figures and tables). In summary, any data and software utilized in the work contained in the manuscript must be documented for free and open availability. Data or software that are sensitive and require restrictions on access (e.g., personal data, medical information, fossil locations, strategic models) must be preserved in a repository with appropriate access controls. 2. Availability Statement in Open Research Section (required) a. Data Availability Statement (required): A Data Availability Statement is required in the Open Research section of your paper describing where and how your data are available, including an online means to access your data. Check links and files before submitting your paper to the journal so as to ensure the data are accessible for peer review. Many data repositories provide confidential data access for this purpose. For data that are not publicly available, sensitive, or restricted, examples, templates, and specific guidance are provided in this document. b. Software Availability Statement (required): A Software Availability Statement is required in the Open Research section of your paper for software that is central to your research such as for model simulations, data analysis, data visualization, and model output analysis. The Availability Statement should contain a citation, licensing information, access restrictions, and a link to the development platform (e.g. GitHub). Note that "git/GitHub/GitLab" are not acceptable software repositories because they are not archival. For software that are not publicly available, sensitive, or restricted, examples, templates, and specific guidance, are provided in this document.
Bulletin of the American Physical Society, Mar 6, 2018
Proceedings, May 1, 2021
As a marginal sea connected to neighboring basins through straits, the Gulf of Mexico (GoM) is dy... more As a marginal sea connected to neighboring basins through straits, the Gulf of Mexico (GoM) is dynamically and topographically complex. Physical processes are strongly influenced by the interaction of circulation in the GoM deep basin interior and in the surrounding shelf areas of diverse morphologies that include deltas, estuaries, barrier islands and marshes. This was particularly evident during the 2010 Deepwater Horizon (DwH) incident, a deep blow-out close to the Northern GoM shelves, over an area strongly affected by the brackish river plume originated from the Mississippi River Delta. The specific physical conditions are revisited, to illustrate the synergy between the evolution of the Loop Current-Florida Current system and the rapidly changing shelf and coastal currents under the influence of river runoff and winds. Each of these physical factors had been studied prior to the DwH incident, but their combined effects on hydrocarbon pathways were not known. Examples are given on what has been learned through research under the Gulf of Mexico Research Initiative (GoMRI) in the last 10 years. The focus is on transport processes in the GoM along the ocean continuum from the deep basin interior to the coastal and
Journal of the Acoustical Society of America, Oct 1, 2022
Accurate numerical simulations of underwater acoustic propagation in a dynamic ocean—and its asso... more Accurate numerical simulations of underwater acoustic propagation in a dynamic ocean—and its associated uncertainty—require using realistic environmental parameters as inputs and especially a high-fidelity representation of the expected spatio-temporal variability of the ocean sound speed in the volume of interest. In areas characterized by strong temperature and salinity variations (e.g., associated with long-living mesoscale eddies in the Gulf of Mexico), the approximate simulation of the 3D sound-speed field and its variability requires predictive oceanographic models capable of resolving such variations. This study investigates the impact of vertical resolution focusing on how it shapes the representation of the 3D sound speed variability through a suite of simulations of the northern Gulf of Mexico performed with a regional ocean model run at submesoscale permitting horizontal resolution (0.5 km) using increasing vertical resolution from 30 to 200 terrain-following layers over a one-month simulation interval (as described in the companion paper presented by Touret et al.). Geo-acoustic parameters were matched to the existing sediment database. In selected areas influenced by mesoscale eddies, ray tracing is used to determine the significance of increased resolution on acoustic propagation as a function of the sensor configurations and the expected sound speed variability.
Journal of the Acoustical Society of America, Oct 1, 2022
Vertical resolution affects the representation of ocean sound speed according to a suite of regio... more Vertical resolution affects the representation of ocean sound speed according to a suite of regional simulations of the De Soto Canyon circulation in the Gulf of Mexico. Simulations have identical horizontal resolution of 0.5 km, partially resolving submesoscale dynamics, and increasing vertical resolution from 30 (i.e., comparable to what commonly used in mesoscale permitting or resolving hindcast and forecast products such as HYCOM) to 200 terrain-following layers. Simulations with 30- and 70-layers underestimate the ageostrophic contributions in and around the eddies below the mixed-layer and do not reproduce the sharp vorticity and density variations associated with the mesoscale circulations compared to the 140- and 200-layers runs. The ocean sound speed (based on the classical MacKenzie formula) was found to be far more variable when the submesoscale, ageostrophic circulations are captured also in their vertical structure and vertical contributions to the density field. Hence, the results of this study indicate that to better predict the influence of the submesocale oceanic circulation on ocean sound speed variability, model simulations should consider enhancing both horizontal and vertical resolution to resolve at least the first 3 baroclinic modes. To do so, more than 100 vertical layers were found to be needed in this study.
Authorea (Authorea), Mar 26, 2023
Diatoms are among the most efficient marine organisms for primary production and carbon sequestra... more Diatoms are among the most efficient marine organisms for primary production and carbon sequestration, absorbing at least 10 billion tonnes of carbon dioxide every year. Yet, the spatial distributions of these planktonic organisms remain puzzling and the underlying physical processes poorly known. Here we investigate what dynamical conditions are conductive to episodic diatom blooms in oligotrophic waters based on Lagrangian diagnosis and satellite-derived phytoplankton functional types and ocean currents. The Lagrangian coherence of the flow is diagnosed in space and time simultaneously to identify which structures favor diatom growth. Observations evidence that flow structures with a high degree of coherence (40 days or longer) in high turbulent kinetic energy and vorticity sustain high concentrations of diatoms in the sunlite layers. Our findings show that the integration of Eulerian kinematic variables into a Lagrangian frame allows revealing new dynamical aspects of geophysical turbulence and unveil transport properties having large biological impacts.
arXiv (Cornell University), Oct 7, 2021
The threat of global warming and the demand for reliable climate predictions pose a formidable ch... more The threat of global warming and the demand for reliable climate predictions pose a formidable challenge being the climate system multiscale, high-dimensional and nonlinear. Spatiotemporal recurrences of the system hint to the presence of a low-dimensional manifold containing the highdimensional climate trajectory that could make the problem more tractable. Here we argue that reproducing the geometrical and topological properties of the low-dimensional attractor should be a key target for models used in climate projections. In doing so, we propose a general data-driven framework to characterize the climate attractor and showcase it in the tropical Pacific ocean using a reanalysis as observational proxy and two state-of-the-art models. The analysis spans four variables simultaneously over the periods 1979-2019 and 2060-2100. At each time t, the system can be uniquely described by a state space vector parameterized by N variables and their spatial variability. The dynamics is confined on a manifold with dimension lower than the full state space that we characterize through manifold learning algorithms, both linear and nonlinear. Nonlinear algorithms describe the attractor through fewer components than linear ones by considering its curved geometry, allowing for visualizing the high-dimensional dynamics through low-dimensional projections. The local geometry and local stability of the high-dimensional, multi-variable climate attractor are quantified through the local dimension and persistence metrics. Model biases that hamper climate predictability are identified and found to be similar in the multivariate attractor of the two models during the historical period while diverging under the warming scenario considered. Finally, the relationships between different sub-spaces (univariate fields), and therefore among climate variables, are evaluated. The proposed framework provides a comprehensive, physically based, test for assessing climate feedbacks and opens new avenues for improving their model representation.
Frontiers in Marine Science, Dec 10, 2021
Fine-scale larval dispersal and connectivity processes are key to species survival, growth, recov... more Fine-scale larval dispersal and connectivity processes are key to species survival, growth, recovery and adaptation under rapidly changing disturbances. Quantifying both are required to develop any effective management strategy. In the present work, we examine the dispersal pattern and potential connectivity of a common deepwater coral, Paramuricea biscaya, found in the northern Gulf of Mexico by evaluating predictions of physical models with estimates of genetic connectivity. While genetic approaches provide estimates of realized connectivity, they do not provide information on the dispersal process. Physical circulation models can now achieve kilometerscale resolution sufficient to provide detailed insight into the pathways and scales of larval dispersal. A high-resolution regional ocean circulation model is integrated for 2015 and its advective pathways are compared with the outcome of the genetic connectivity estimates of corals collected at six locations over the continental slope at depths comprised between 1,000 and 3,000 m. Furthermore, the likely interannual variability is extrapolated using ocean hindcasts available for this basin. The general connectivity pattern exhibits a dispersal trend from east to west following 1,000 to 2,000-m isobaths, corresponding to the overall westward near-bottom circulation. The connectivity networks predicted by our model were mostly congruent with the estimated genetic connectivity patterns. Our results show that although dispersal distances of 100 km or less are common, depth differences between tens to a few hundred meters can effectively limit larval dispersal. A probabilistic graphic model suggests that stepping-stone dispersal mediated by intermediate sites provides a likely mechanism for long-distance connectivity between the populations separated by distances of 300 km or greater, such as those found in the DeSoto and Keathley canyons.
Climate Dynamics, Nov 15, 2022
Earth’s Future, Nov 1, 2018
During recent decades, through theoretical considerations and analyses of observations and model ... more During recent decades, through theoretical considerations and analyses of observations and model simulations, the scientific community has fundamentally advanced our understanding of the coupled climate system, thereby establishing that humans affect the Earth's climate. Resulting from this remarkable accomplishment, the COP21 agreement marks a historic turning point for climate research by calling for actionable regional climate change information on time scales from seasonal to centuries for the benefit of humanity, as well as living and nonliving elements of the Earth environment. Out of the underlying United National Framework Convention on climate Change process, improving seamless regional climate forecast capabilities emerges as a key challenge for the international research community. Addressing it requires a multiscale approach to climate predictions. Here we offer a vision that emphasizes enhanced scientific understanding of regional to local climate processes as the foundation for progress. The scientific challenge is extreme due to the rich complexity of interactions and feedbacks between regional and global processes, each of which affects the global climate trajectory. To gain the necessary scientific insight and to turn it into actionable climate information require technical development, international coordination, and a close interaction between the science and stakeholder communities. Plain Language Summary During recent decades, through theoretical considerations and analyses of observations and model simulations, the scientific community has fundamentally advanced our understanding of the coupled climate system, thereby establishing that humans affect the Earth's climate. Building on this remarkable accomplishment, the COP21 agreement marks a historic turning point for climate research by calling for actionable regional climate change information on time scales from seasonal to centuries for the benefit of humanity and the full biosphere. Out of the underlying United National Framework Convention on climate Change process, improving seamless regional climate forecast capabilities emerges as a closely linked challenge for the international research community. Addressing this challenge requires a multiscale approach to climate predictions. Here we offer a vision for realizing an approach that emphasizes enhanced scientific understanding of regional to local climate processes as the foundation for progress. The scientific challenge is extreme due to the rich complexity of interactions and feedbacks between regional and global processes, each of which affects the global climate trajectory. Technical development, international coordination, and a close interaction between the science and stakeholder communities are also required. In their absence scientific insight cannot be gained or turned into actionable climate information.
Journal Of Geophysical Research: Oceans, Jun 1, 2019
Coastal waters in the Labrador Sea are influenced by the seasonal input of meltwater from the Gre... more Coastal waters in the Labrador Sea are influenced by the seasonal input of meltwater from the Greenland ice sheet, which is predicted to more than double by the end of the century. Mechanisms controlling the offshore export of meltwater can have a significant effect on stratification and vertical stability in the Labrador Sea, being particularly important if the meltwater is transported toward the interior of the basin where winter convection occurs. Here we use a high-resolution ocean model to show that coastal upwelling winds play a critical role transporting the meltwater offshore to about 150 km from the coast, where increased eddy activity and mean circulation can then transport the meltwater farther offshore. While meltwater discharged from West Greenland is either transported to Baffin Bay or circumnavigates the basin flowing mostly along isobaths, meltwater from East Greenland can reach the interior of the basin where it may influence stratification and winter convection whenever winds are anomalously upwelling favorable in late summer and early fall. Plain Language Summary Every summer, coastal waters off Greenland are influenced by the input of freshwater from ice sheet melting. Based on analyses of ocean model simulations, we show that meltwater transport in the Labrador Sea is controlled by multiple processes. Winds play an important role, transporting the freshwater to about 150 km from the coast, where the large-scale circulation and eddies can transport the meltwater farther offshore. Most of the meltwater is transported either northward into Baffin Bay or around the basin. When winds are anomalously upwelling favorable in late summer or early fall, however, meltwater from East Greenland can be transported into the interior of the basin where it may influence vertical stratification and winter convection.