French Research Institute for Exploitation of the Sea
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Product User Manual. In Situ TAC T&S REP Product INSITU_GLO_PHY_TS_DISCRETE_MY_013_001 called CORA
No full textThis Product User Manual describes the CORA-GLOBAL dataset and the additional dataset EasyCORA (subset of the previous one with best quality). These datasets are distributed as part of the product INSITU_GLO_PHY_TS_DISCRETE_MY_013_001 in the Copernicus Marine catalogue. This document explains how the datasets are build, what the content is, which data services are available to have access to the data
Processing BGC-Argo pH data at the DAC level
No full textSeawater proton concentration is a master variable that controls the air-sea gas exchange of CO2, the ability of organisms to produce calcium carbonate shells, and that tracks the production and respiration of organic carbon as CO2 is removed or added to water by biological processes. The proton concentration in seawater [H+] (mol kg-seawater-1) is typically reported as the pH = -log10 [H+]. The in situ proton concentration ranges from about 3 to 30 nmol kg-seawater-1 (7.5<pH<8.5).
Seawater pH is measured from profiling floats using a Deep-Sea DuraFET pH sensor that is manufactured at MBARI (Johnson et al., 2016) or at Sea-Bird Scientific (Float pH). The core of each sensor is an Ion Sensitive Field Effect Transistor (ISFET), produced by Honeywell, that responds to proton activity and a Ag/AgCl reference electrode that responds to chloride ion activity. When properly calibrated, the sensor measures the activity of HCl, which is the product of the activities of the two ions aH+ × aCl- (Martz et al., 2010)
Copernicus Marine In Situ TAC NetCDF Format Manual
No full textThis document specifies the NetCDF file format of Copernicus Marine In Situ used to distribute ocean in situ data and metadata. It documents the standards used herein; this includes naming conventions as well as metadata content. It was initiated in March 2019, based on OceanSITES and Argo user's manuals. This document is meant to be understood as purely format oriented; the scope is limited to just the syntax. Content, rules and relevant information is supported by VI. REFERENCES. Note on versions It is used Semantic Versioning (https://semver.org/) given a version number MAJOR.MINOR.PATCH, increment the: ● MAJOR version when you make incompatible API changes ● MINOR version when you add functionality in a backwards compatible manner ● PATCH version when you make backwards compatible bug fixes Additional labels for pre-release and build metadata are available as extensions to the MAJOR.MINOR.PATCH format. Note on updates In order to assure the stability of the format version, a maximum of one new minor version will be released every 6 months and a major version every 2 years, only when required
New age constraints for glacial terminations IV, III, and III.a based on Western Mediterranean speleothem records
No full textThe full understanding of climate feedbacks responsible for the amplification of deglaciations requires robust chronologies for these climate transitions, but, in the case of marine records, radiocarbon chronologies are possible only for the last glacial termination. Although the assumed relationships between the marine isotopic record and the orbital parameters provide a first order chronology for the previous terminations, an independent chronological control allows the relationships between orbital forcing and the climate response to be assessed over multiple previous terminations. Here we present new geochemical records of Marine Isotope Stages 11 to 7 from a western Mediterranean speleothem, establishing a new long terrestrial climate record for this region. Its absolute U/Th dates provide an exceptional chronology for the glacial terminations IV, III, and III.a. The onset of these three glacial terminations was marked by rapid δ18O depletions, reflecting ocean freshening by ice melting, thus providing an excellent tie point for regional marine records also sensitive to such freshening. These new chronologies reveal an earlier onset of the deglacial melting for the TIV and TIII.a in contrast to the generally accepted marine chronologies and indicate that the duration of these deglaciations was variable, with TIV particularly longer (~20 kyr). This study also supports that the onset of deglacial melting always occurred during declining precession index while a nonunique relation occurred with the obliquity parameter
Vertical Mixing Can Both Induce and Inhibit Submesoscale Frontogenesis
No full textPast studies separately demonstrate that vertical boundary layer turbulence can either sharpen or weaken submesoscale fronts in the surface mixed layer. These studies invoke competing interpretations that separately focus on the impact of either vertical momentum mixing or vertical buoyancy mixing, where the former can favor sharpening (frontogenesis) by generation of an ageostrophic secondary circulation, while the latter can weaken the front (frontolysis) via diffusion or shear dispersion. No study comprehensively demonstrates vertical mixing induced frontogenesis and frontolysis in a common framework. Here, we develop a unified paradigm for this problem with idealized simulations that explore how a front initially in geostrophic balance responds to a fixed vertical mixing profile. We evolve 2D fronts with the hydrostatic, primitive equations over a range of Ekman (Ek = 10−4 – 10−1) and Rossby numbers (Ro = 0.25–2), where Ek quantifies the magnitude of vertical mixing and Ro quantifies the initial frontal strength. We observe vertical momentum mixing induced, nonlinear frontogenesis at large Ro and small Ek and inhibition of frontogenesis via vertical buoyancy diffusion at small Ro and large Ek. Symmetric instability can dominate frontogenesis at very small Ek; however, the fixed mixing limits interpretation of this regime. Simulations that suppress vertical buoyancy mixing are remarkably frontogenetic, even at large Ek, explicitly demonstrating that buoyancy mixing is frontolytic. Application of two scalings to quantify the competition between cross-front buoyancy advection and vertical diffusion identifies practically equivalent controlling parameters (Ro2/Ek, Ro/Ek1/2); these ratios approximately map regime transitions across simulations with equal vertical eddy viscosity and diffusivity
How well do AMIP6 and CMIP6 reproduce the specific Extreme El Niño teleconnections to North America ?
No full textExtreme El Niño events (e.g., 1982–1983, 1997–1998) are characterized by strong, eastward-shifted warm Sea Surface Temperature anomalies, and a southward migration of the eastern Pacific Inter-Tropical Convergence Zone (ITCZ) to the equator. Using an ensemble simulation with a single AMIP6 model, Beniche et al. (2024, https://doi.org/10.1038/s41598-024-52580-9) suggested that such events uniquely yield an eastward shift of the Pacific-North American (PNA) teleconnection pattern, with specific impacts over North America. Here, we first examine the robustness of these results in 135 ensemble members from 23 different AMIP6 models. The specific, eastward-shifted extreme El Niño teleconnection pattern is robust in all models but one. It is also highly reproducible across years and ensemble members, due to stronger teleconnection amplitude than that of internal atmospheric noise. This yields specific, predictable impacts (defined as
0.5 STD) such as warm conditions over Northeast America (69% chances), and wet anomalies over California (77%) and Florida (97%). We then show that 26 out of the 42 CMIP6 models we examined reproduce extreme El Niño events, defined as El Niño events associated with large eastern Pacific rainfall anomalies. These models tend to have a weaker cold tongue bias than the rest of CMIP6. Despite a degradation in performance from AMIP6 to CMIP6, 18 out of the 26 selected models capture the specific extreme El Niño teleconnections, albeit with some underestimation of wet anomalies over California and Florida. We end by discussing implications for future North American climate projections based on CMIP6.
Key Points
In 22/23 AMIP6 ensemble simulations, the North American ENSO teleconnection pattern only shifts eastward during extreme El Niño events
The extreme El Niño teleconnection pattern and its impacts (warm Northeast America, wet California and Florida) are very reproducible
Most CMIP6 models that produce extreme El Niño events reproduce their teleconnection pattern, but downplay wet California/Florida anomalies
Plain Language Summary
The El Niño-Southern Oscillation (ENSO) alternates between a warm and wet (El Niño) or cold and dry (La Niña) central-eastern equatorial Pacific. ENSO events modify the atmospheric circulation, leading to climate impacts over remote regions, including North America. This is known as ENSO teleconnections. Occasionally, El Niño escalates into extreme events, characterized by strong and eastward-shifted equatorial Pacific warm anomalies compared to weaker events. By analyzing a large database of atmospheric models forced by observed Sea Surface Temperature, we demonstrate that these extreme El Niño events produce North American teleconnection pattern and impacts that are distinct from those of milder events, and more reproducible. Extreme El Niño in particular results in high probability of warm anomalies over Northeast America and wet anomalies over California and Florida. Not all coupled ocean-atmosphere climate models can simulate extreme El Niño events, but most of those that do reproduce their specific teleconnection pattern, albeit with underestimations of wet conditions over California and Florida. We discuss the implications of our results for future projections of the North American climate
Turbulent dissipation along contrasting internal tide paths off the Amazon shelf from AMAZOMIX
No full textThe Amazon shelf break is a key oceanic region where strong internal tides (ITs) are generated, playing a substantial role in climate processes and ecosystems through vertical dissipation and mixing. During the AMAZOMIX survey (2021), currents, hydrography, and turbulence were measured over the M2 tidal period (12.42 h) at multiple stations along both high (HTE) and low (LTE) tidal energy paths, covering IT generation and propagation regions off the Amazon shelf. This dataset provides a unique opportunity to assess IT-driven vertical dissipation and quantify its spatial extent and influence in the region.
Microstructure analyses, integrated with hydrographic data, highlighted contrasting dissipation rates. The highest rates occurred at IT generation sites along the HTE paths, while the lowest rates were observed on the slope along the LTE path. Near generation sites, the dissipation rates were elevated, [10−6] W kg−1, with IT shear contributing ∼60 % compared to the mean baroclinic current (MBC) shear. Along IT paths, rates decreased to [10−8] W kg−1 but remained substantial, driven by nearly equal contributions from IT and MBC shear.
A key finding was the relative increase in turbulent dissipation ([10−7] W kg−1) ∼230 km from two distinct IT generation sites at the shelf break. This zone of high mixing was located in an area where the general circulation vanished, coinciding with a region of potential constructive interference of IT rays originating from different generation sites. It also aligned with the occurrence of large-amplitude internal solitary waves (ISWs), suggesting that constructive IT ray interference may generate nonlinear ISWs that lead to enhanced dissipation
Decadal changes in phytoplankton functional composition in the Eastern English Channel: possible upcoming major effects of climate change
No full textGlobal change is known to exert a considerable impact on marine and coastal ecosystems, affecting various parameters such as sea surface temperature (SST), runoff, circulation patterns and the availability of limiting nutrients (like nitrogen, phosphorus and silicon), with each influencing phytoplankton communities differently. This study is based on weekly to fortnightly in vivo fine-spatial-resolution (∼ 1 km) phytoplankton observations along an nearshore–offshore gradient in the French waters of the Eastern English Channel in the Strait of Dover. The phytoplankton functional composition was addressed by automated “pulse-shape recording” flow cytometry, coupled with the analysis of environmental variables over the last decade (2012–2022). This method allows for the characterization of almost the entire phytoplankton size range (from 0.1 to 800 µm width) and the determination of the abundance of functional groups based on optical single-cell signals (fluorescence and scatter). We explored seasonal, spatial and decadal dynamics in an environment strongly influenced by tides and currents. Over the past 11 years, the SST has shown an increasing trend at all stations, with nearshore waters warming faster than offshore waters (+1.05 °C vs. +0.93 °C). Changes in nutrient concentrations have led to imbalances in nutrient ratios () relative to reference nutrient ratios. However, a return to balanced ratios has been observed since 2019. The phytoplankton total abundance has also increased over the aforementioned decade, with a higher contribution of small-sized cells (picoeukaryotes and picocyanobacteria) and a decrease in microphytoplankton, particularly near the coast. Based on an analysis of environmental parameters and phytoplankton abundance, the winters of 2013–2014 and 2019–2020 were identified as shifting periods in this time series. These changes in the phytoplankton community, favoring the smallest groups, could lead to a reduction in the productivity of coastal marine ecosystems, which could, in turn, affect higher trophic levels and the entire food web
Peak glacial-to-Heinrich-1 changes in Denmark Strait Overflow and seawater stratification in the Nordic Seas, a switchboard of changes in Atlantic Meridional Overturning Circulation and the 'Nordic Heat Pump'
No full textToday, the sub-surface Denmark Strait Over ow (DSO) and the Iceland Scotland Over ow form the starting points of Atlantic Meridional Overturning Circulation and compensate for the poleward owing Norwegian and Irminger branches of the North Atlantic surface current that drive the 'Nordic Heat Pump'. During peak glacial and early deglacial times, ice sheets on Iceland and Greenland, and ice-induced isostatic and eustatic sea-level changes reduced the Denmark Strait aperture and DSO. Nonetheless, extremely high benthic stable carbon and oxygen isotope values together with very high ventilation ages of bottom waters re ect a north-south density gradient of intermediate-waters and persistent ow of partially Arctic-sourced waters through both the Denmark Strait and the Faeroe Channel, similar to today. The rst arrival of Heinrich -1 meltwaters northwest of Iceland, arriving from the southwest around 18.4 cal ka, accompanied a tipping point in DSO circulation, documented by reduced ventilation and ventilation ages, a 3°C warming, and increased radiogenic Nd isotope signatures in sediments at lu -side Site PS2644. These records suggest a sudden subsurface incursion of Atlantic intermediate waters across basaltic sediments from S.E. of Iceland. Deep-water convection o Norway then was replaced by weak brine water formation, coeval with a breakdown of the 'Nordic Heat Pump' evidenced by a temperature drop on Greenland. After 16.2 cal. ka, a major meltwater outbreak from the Barents ice shelf led to modi ed Heinrich-1-style circulation until ~15.1 cal ka. Vice-versa, the DSO intensi ed during interstadial and Holocene times, then causing sediment hiatuses at site PS2644
Physiological responses of Starry Sturgeon (Acipenser stellatus) juvenile to thermal stress: exploring the effects of Amygdalin in enhancing Sturgeon resilience
No full textThe Acipenseridae is a crucial inhabitant of aquatic ecosystems, and environmental adversity can have harmful consequences on their health. Stress-relieving compounds and immune system stimulants are currently used to support fish resistance. This study aimed to investigate the metabolic and immune responses to thermal stress in starry sturgeon juvenile previously exposed to amygdalin as a stress-reducing compound. The juveniles were treated at different temperatures (18°C, 22°C, and 26°C) with or without amygdalin, with three replicates. Blood and liver tissue samples were collected, and various parameters were measured. The results revealed significant differences in serum enzymes, cortisol levels, antioxidant capacity, and immune system components among the different groups. It was evident that fish pre-treated with amygdalin and kept at 22 °C (A+T22) and 26 °C (A+T26) experienced a significant decline in ALT (alanine aminotransferase, AST (aspartate aminotransferase) and T-AOC (Total Antioxidant Capacity) levels compared to those who did not undergo such treatment (fish kept at 22 and 26°C). Moreover, when comparing amygdalin-exposed fish at 26°C with their counterparts who were not exposed to amygdalin, there was a noticeable decrease in ALP and cortisol levels. Thermal stress has an adverse effect on the immune parameters of starry sturgeon. However, when amygdalin is administered, it has the potential to enhance fish resilience against thermal stressors by increasing immunity, particularly in C3 and IgM. In conclusion, amygdalin could serve as a beneficial agent for fish by mitigating stress levels and enhancing their resilience against thermal stressor