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The Global Ocean Data Analysis Project (GLODAP) is a synthesis effort providing regular compilations of surface to bottom ocean biogeochemical bottle data, with an emphasis on seawater inorganic carbon chemistry and related variables determined through chemical analysis of seawater samples. GLODAPv2.2023 is an update of the previous version, GLODAPv2.2022 (Lauvset et al., 2022). The major changes are as follows: data from 23 new cruises were added. In addition, a number of changes were made to the data included in GLODAPv2.2022. GLODAPv2.2023 includes measurements from more than 1.4 million water samples from the global oceans collected on 1108 cruises. The data for the now 13 GLODAP core variables (salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon, total alkalinity, pH, chlorofluorocarbon-11 (CFC-11), CFC-12, CFC-113, CCl 4 , and SF 6) have undergone extensive quality control with a focus on the systematic evaluation of bias. The data are available in two formats: (i) as submitted by the data originator but converted to World Ocean Circulation Experiment (WOCE) exchange format and (ii) as a merged data product with adjustments applied to minimize bias. For the present annual update, adjustments for the 23 new cruises were derived by comparing those data with the data from the 1085 quality-controlled cruises in the GLODAPv2.2022 data product using crossover analysis. SF 6 data from all cruises were evaluated by comparison with CFC-12 data measured on the same cruises. For nutrients and ocean carbon dioxide (CO 2), chemistry comparisons to estimates based on empirical algorithms provided additional context for adjustment decisions. The adjustments that we applied are intended to remove potential biases from errors related to measurement, calibration, and data-handling practices without removing known or likely time trends or variations in the variables evaluated. The compiled and adjusted data product is believed to be consistent to better than 0.005 in salinity, 1 % in oxygen, 2 % in nitrate, 2 % in silicate, 2 % in phosphate, 4 µ mol kg -1 in dissolved inorganic carbon, 4 µ mol kg -1 in total alkalinity, 0.01–0.02 in pH (depending on region), and 5 % in the halogenated transient tracers. The other variables included in the compilation, such as isotopic tracers and discrete CO 2 fugacity (f CO 2), were not subjected to bias comparison or adjustments. The original data, their documentation, and DOI codes are available at the Ocean Carbon and Acidification Data System of NOAA National Centers for Environmental Information (NCEI), which also provides access to the merged data product. This is provided as a single global file and as four regional ones – the Arctic, Atlantic, Indian, and Pacific oceans – under https://doi.org/10.25921/zyrq-ht66 (Lauvset et al., 2023). These bias-adjusted product files also include significant ancillary and approximated data, which were obtained by interpolation of, or calculation from, measured data. This living data update documents the GLODAPv2.2023 methods and provides a broad overview of the secondary quality control procedures and results. [ABSTRACT FROM AUTHOR]

In recent decades the decline of the Arctic sea ice has modified vertical momentum fluxes from the atmosphere to the ice and the ocean, thereby affecting the surface circulation. In the past ten years satellite altimetry has contributed to understand these changes. However, data from ice-covered regions require dedicated processing, originating inconsistency between ice-covered and open ocean regions in terms of biases, corrections and data coverage. Thus, efforts to generate consistent Arctic-wide datasets are still required to enable the study of the Arctic Ocean surface circulation at basin-wide scales. Here we provide and assess a monthly gridded dataset of sea surface height anomaly and geostrophic velocity. This dataset is based on Cryosat-2 observations over ice-covered and open ocean areas of the Arctic up to 88° N for the period 2011 to 2018, interpolated using the Data-Interpolating Variational Analysis (DIVA) method. Geostrophic velocity was not available north of 82° N before this study. To examine the robustness of our results, we compare the generated fields to one independent altimetry dataset and independent data of ocean bottom pressure, steric height and near-surface ocean velocity from moorings. Results from the comparison to near-surface ocean velocity show that our geostrophic velocity fields can resolve seasonal to interannual variability of boundary currents wider than about 50 km. We further discuss the seasonal cycle of sea surface height and geostrophic velocity in the context of previous literature. Large scale features emerge, i.e. Arctic-wide maximum sea surface height between October and January, with the highest amplitude over the shelves, and basin wide seasonal acceleration of Arctic slope currents in winter. We suggest that this dataset can be used to study not only the large scale sea surface height and circulation but also the regionally confined boundary currents. The dataset is available in netCDF format from PANGAEA at [data currently under review]. [ABSTRACT FROM AUTHOR]

Sedimentary 231Pa / 230Th ratios provide clues to estimate the strength of past ocean circulation. For its estimation, understanding the processes controlling the distributions of dissolved 231Pa and 230Th in the ocean is important. However, simulations of dissolved and particulate 231Pa and 230Th in the modern ocean, recently obtained from the GEOTRACES project, remain challenging. Here we show an improved model simulation of 231Pa and 230Th in the global ocean by introducing bottom scavenging and the dependence of scavenging efficiency on particle concentration with water-column reversible scavenging. The incorporation of bottom scavenging improves the simulated distribution of dissolved 231Pa and 230Th in the deep ocean, which has been overestimated in models not considering the bottom scavenging. We further demonstrate that introducing the dependence of scavenging efficiency on particle concentration results in a high concentration of dissolved 230Th in the Southern Ocean. Our best simulation can well reproduce not only the oceanic distribution of 231Pa and 230Th but also the sedimentary 231Pa / 230Th ratios. Sensitivity analysis reveals that oceanic advection of 231Pa primarily determines sedimentary 231Pa / 230Th ratios. On the other hand, 230Th advection and bottom scavenging have an opposite effect to 231Pa advection on the sedimentary 231Pa / 230Th ratios, reducing their latitudinal contrast. Our model realistically simulates the residence times of 231Pa and 230Th, whereas previous models that reported the similar distribution of sedimentary 231Pa / 230Th ratios significantly overestimate the residence times for both 231Pa and 230Th. [ABSTRACT FROM AUTHOR]

In recent decades, rapid ice shelf disintegration along the Antarctic Peninsula has had a global impact through enhancing outlet glacier flow and hence sea level rise and the freshening of Antarctic Bottom Water. Ice shelf thinning due to basal melting results from the circulation of relatively warm water in the underlying ocean cavity. However, the effect of sub-shelf circulation on future ice shelf stability cannot be predicted accurately with computer simulations if the geometry of the ice shelf cavity is unknown. To address this deficit for Larsen C Ice Shelf, West Antarctica, we integrate new water column thickness measurements from recent seismic campaigns with existing observations. We present these new data here along with an updated bathymetry grid of the ocean cavity. Key findings include a relatively deep seabed to the southeast of the Kenyon Peninsula, along the grounding line and around the key ice shelf pinning-point of Bawden Ice Rise. In addition, we can confirm that the cavity's southern trough stretches from Mobiloil Inlet to the open ocean. These areas of deep seabed will influence ocean circulation and tidal mixing and will therefore affect the basal-melt distribution. These results will help constrain models of ice shelf cavity circulation with the aim of improving our understanding of sub-shelf processes and their potential influence on ice shelf stability. The datasets are comprised of all the new point measurements of seabed depth. We present the new depth measurements here, as well as a compilation of previously published measurements. To demonstrate the improvements to the sub-shelf bathymetry map that these new data provide we include a gridded data product in the Supplement of this paper, derived using the additional measurements of both offshore seabed depth and the thickness of grounded ice. The underlying seismic datasets that were used to determine bed depth and ice thickness are available at 10.5285/315740B1-A7B9-4CF0-9521-86F046E33E9A (Brisbourne et al., 2019), 10.5285/5D63777D-B375-4791-918F-9A5527093298 (Booth, 2019), 10.5285/FFF8AFEE-4978-495E-9210-120872983A8D (Kulessa and Bevan, 2019) and 10.5285/147BAF64-B9AF-4A97-8091-26AEC0D3C0BB (Booth et al., 2019). [ABSTRACT FROM AUTHOR]

In recent decades, rapid ice-shelf disintegration along the Antarctic Peninsula has had a global impact through enhancing outlet glacier flow, and hence sea level rise, and the freshening of Antarctic Bottom Water. Ice shelf thinning due to basal melting results from the circulation of relatively warm water in the underlying ocean cavity. However, the effect of sub-shelf circulation on future ice-shelf stability cannot be predicted accurately with computer simulations if the geometry of the ice-shelf cavity is unknown. To address this deficit for Larsen C Ice Shelf, west Antarctica, we integrate new water-column thickness measurements with existing observations. We present these new data here along with an updated bathymetry grid of the ocean cavity. Key findings include relatively deep seabed to the south-east of the Kenyon Peninsula, along the grounding line and around the key ice shelf pinning point of Bawden Ice Rise. In addition, we can confirm that the cavity’s southern trough stretches from Mobiloil Inlet to the open ocean. These areas of deep seabed will influence ocean circulation and tidal mixing, and will therefore affect the basal-melt distribution. These results will help constrain models of ice-shelf cavity circulation with the aim of improving our understanding of sub-shelf processes and their potential influence on ice shelf stability. The data set comprises all point measurements of seabed depth and a gridded data product, derived using additional measurements of both offshore seabed depth and the thickness of grounded ice. We present all new depth measurements here as well as a compilation of previously published measurements used in the gridding process. The gridded data product is included in the supplementary material. [ABSTRACT FROM AUTHOR]

Small-scale diapycnal mixing participates to the circulation of the abyssal ocean, and is known to be intensified near the sea-floor, where internal tides are generated and eventually break. Parametrization of this bottom-intensified mixing in global circulation models still needs to be improved, and this requires observations. Such processes are characterized by :- a high level of turbulence, requiring high sampling rate measurements;- intermittency, requiring a large number of samples;- and vertical inhomogeneity, requiring a large number of instruments.To satisfy these constraints, we chose to focus on temperature measurements, by means of innovative and versatile instruments, the High Sampling Rate Thermistors developed at the NIOZ. These autonomous sensors have been successfully used over the last decade in several deep seas and oceans, over a large variety of topographic features (seamounts, banks, trenches, ridges). Typically, one hundred sensors are mounted on a steel cable, moored at the ocean bottom, and measure temperature every second for month- or year-long durations. In the presence of weak stratifications, the 1mK resolution of the sensors is particularly useful. This original dataset gives an insight to phenomena occurring in the abyssal oceanic boundary layer, where tidal and higher frequency internal waves of large amplitude are systematically observed. It also provides via Thorpe scale analysis a quantitative estimation of turbulent dissipation and diffusivity. When averaged in space and time, these quantities confirm that, despite intermittency, vertical turbulent fluxes remain fairly high close to sloping boundaries due to internal wave breaking and subsequent re-stratification. [ABSTRACT FROM AUTHOR]

An extensive grid of seismic reflection data collected on Ekström Ice Shelf, East Antarctica, between 2010–2018, using an on-ice vibroseis source and snowstreamer, are used to make a detailed bathymetry map of the sea floor and ice-shelf cavity. The maps shows a deep sea-floor trough, likely a paleao-ice stream, under the western side of the ice shelf. The trough contains a number of points of higher topography, indicating probable former grounding line positions. At the shelf front a sill running across the width of the shelf has implications for ocean circulation and thus ice-ocean interaction and ice shelf melt. This new bathymetry is markedly different from previous models, which show a generally flat and shallow sea floor in the region. This is presumably the case for many of the smaller ice-shelves in Dronning Maud Land, which highlights the need for better bathymetry measurements in these key threshold regions. [ABSTRACT FROM AUTHOR]

It has been long been recognized that the large-scale circulation of the abyssal ocean isenabled by small-scale diapycnal mixing. Theories developed in the fifties and sixties positedthat the diapycnal mixing drives widespread upwelling of abyssal waters and broad polewardmeridional flows. We will argue that these predictions need to be revised in view ofobservations collected over the last twenty years which suggest that mixing is stronglyenhanced towards the ocean bottom, where the breaking of internal tides and lee waves ismost vigorous. The bottom-intensified mixing induces a a pattern of near-bottom up- anddownwelling that is quite different from the traditionally-assumed widespread upwelling.The up- and downwelling flows result in a horizontal circulation characterized byzonal flows, while the meridional flows are confined along the ocean’s westernboundaries. We will discuss the implications of these circulation patterns for the residencytime of abyssal waters in the ocean and for the role of the abyssal ocean on Earth’sclimate. [ABSTRACT FROM AUTHOR]

The Southern Weddell Sea is a pivotal region for the global ocean circulation, by producing large amount of dense waters, which ultimately sink at the bottom of the oceans, the area is fuelling the overturning circulation. As they are produced on the continental shelf, some amount of dense waters interact with the largest ice-shelf of Antarctica, leading to basal melt and altering the characteristics of the outflowing dense waters. Warmer water located off the continental shelf, can also locally access the base of the ice-shelf, though their access is thought to be very limited in today's climate. A change of warm water access to the ice-shelf base could would dramatically increase basal melt, leading to global and widespread consequences on sea level rise, as well as, on water production. However, the dynamics at play in the blocking or access of warm water towards the ice-shelf base remains poorly described and understood. Here, the circulation of warm water toward ice shelves is studied with a set of experiments in order to understand the parameters governing this circulation. In addition, in situ measurements are also used to understand this circulation : a set of autonomous floats deployed in 2017 have been sampling on the continental shelf for almost a year, providing unprecedented year-round observation of top to bottom ocean characteristics directly next to ice-shelf. Theses floats allows us to describe the seasonal cycle of both the warm water flowing toward the ice shelf draft, and the dense water exiting the ice-shelf and being transformed as deep water on their way out of the Weddell Sea. [ABSTRACT FROM AUTHOR]