Antarctic Mode Water

An estimate of Southern Ocean volume in temperature-salinity (T-S) classes is made with a focus on cold water masses south of the Polar Front, at depths shallower than 2,000 m. The volumetric diagram for waters below 5° C shows a deficit at temperatures near 0° C and 34.2 psu, surrounded by a ring of larger volumes, related to water mass formation near the Polar Front and near the continental margins as well as mixing effects. The cold, fresh extreme of the Antarctic Intermediate Water T-S relation shows a volumetric maximum, apparently distinct from the interior T-S relationship. We identify this mode as Antarctic Mode Water with a volumetric maximum centered near 2.0° C and 33.9 psu. This maximum lies on a large-scale ridge of high volume representing the Antarctic Surface Water mixed layers south of the Polar Front, at the northern edge of the seasonal sea-ice cover. Additional maxima on the diagram near freezing temperatures seem to be related to processes operating on the slope and shelf, though the data coverage in these regions is much reduced. The origin of the Antarctic Mode Water is ultimately due to sea-ice melt, which systematically shifts the T-S relation of surface water to lower salinities, whereas its thickness and distribution is linked to circumpolar northward Ekman transport and the eddy fluxes of the Polar Front

Structure and Variability of the Jan Mayen Current in the Greenland Sea Gyre From a Yearlong Mooring Array

The Jan Mayen Channel is located North of the Jan Mayen Island in the Nordic Seas, and is an important gateway for the exchanges of volume, heat and freshwater between the Greenland and the Norwegian basins via the Jan Mayen Current. Based on observations from moored instruments deployed on the shelf and the continental slope of the Jan Mayen Island from August 2017 to August 2018, we document the mean state and the variability of the currents, temperature and salinity and their associated vertical structure. We found that the main feature of circulation is an intense and permanent south‐eastward jet‐like current centered at 150 m depth, located on the 400 m depth slope, with a maximum mean magnitude of 7 cm·s−1. While the velocities recorded on the shelf are largely constant in speed and direction, without any strong seasonal cycle, the moorings located offshore are capturing larger anomalies on short time scales that are likely the signature of eddies passing across the mooring array. Overall, the variability of the transport across the section is correlated with the large‐scale wind pattern over the Nordic Seas, highlighting that the Jan Mayen Current is part of a complex system of currents that operates at larger scale in the region

The REHAB-LAB model for individualized assistive device co-creation and production

Assistive devices are designed to enhance individuals with disabilities' functional abilities. The rise of 3D printing technology enabled the production of individualized assistive devices (IADs). A REHAB-LAB is intended for IAD provision involving technical referents and occupational therapists. This study aimed to develop the REHAB-LAB logic model; to explore its fidelity and desirability; and to explore the characteristics of arising initiatives of IAD production. The REHAB-LAB logic model development involved stakeholders throughout the research process. A pragmatic multimethod approach followed two phases 1) logic model development and 2) exploration of its fidelity and desirability. The REHAB-LAB logic model presented the resources (equipment, space, human) required to implement IAD provision in a rehabilitation center, and the expected deliverables (activities and outputs). The REHAB-LAB logic model highlights the interdisciplinarity of IAD provision including occupational therapists, doctors, engineers, managers, and technical referents and places the users at the center of the IAD production. Results confirmed the fidelity and desirability of the REHAB-LAB logic model. The REHAB-LAB logic model can be used as a reference for future healthcare organizations wishing to implement an IAD provision. This research highlighted the interest of IAD provision based on the REHAB-LAB model involving users and transdisciplinary practice

Synchronized autonomous sampling reveals coupled pulses of biomass and export of morphologically different diatoms in the Southern Ocean

The Southern Ocean hosts a large diversity of diatoms that play a major role in carbon fluxes. How the seasonal dynamics in the abundance of specific taxa in surface waters are linked to their contribution to carbon export remains, however, poorly understood. We present here synchronized observations from autonomous samplers deployed in the mixed layer (42 m) and at depth (300 m) during an entire productive season (October 2016 to March 2017) in the iron fertilized region of the central plateau of Kerguelen. Microscopic observations of surface water collected every 11 d revealed 30 different diatom taxa, each contributing to > 1% of total carbon biomass throughout the season. The synchronized sampling revealed a common pattern for diatom taxa belonging to 12 different genera, consisting, for a given taxon, in short pulses of abundance in surface waters followed by export. We explain these coupled dynamics by the formation of aggregates that are produced when a critical diatom cell abundance is reached. This control of the maximum abundance of a given diatom drives the seasonal change in the slope of the size‐class distribution of the diatom community. It further constrains the total carbon diatom biomass in a narrow range of values due to the inverse relationship between total diatom abundance and their community‐weighted mean biomass. This coupling let us conclude that aggregate formation, and the export to depth, occurs throughout the season for diatoms with different morphologies

Southern Ocean

International audienc

Observing the Antarctic continental shelf with CTD-instrumented elephant seals

Since 2004, several hundreds of diving marine animals, mainly Antarctic and Arctic seals, were fitted with a new generation of Argos-CTD tags developed by the Sea Mammal Research Unit of the University of St. Andrews in Scotland. These tags can be used to investigate simultaneously the at-sea ecology of these animals while collecting valuable oceanographic data. Some of these species are able to travel thousands of kilometres, continuously diving to great depths (590 ± 200 m, with maxima around 2000m). Through the years, these animals have become an essential source of temperature and salinity profiles (MEOP-CTD database available at http://www.meop.net), especially for the polar oceans, complementing efficiently the Argo array. One region where the use of instrumented seals has been particularly successful is the Antarctic continental shelf. Recent contributions to the study of the Antarctic Bottom Water production area near Prydz Bay, the rapidly-thinning ice shelves in Amundsen Bay, or the stratification in the marginal ice zone, are demonstrating the rapidly growing value of these data for Polar Research

Reemergence of Antarctic sea ice predictability and its link to deep ocean mixing in global climate models

Satellite observations show a small overall increase in Antarctic sea ice extent (SIE) over the period 1979–2015. However, this upward trend needs to be balanced against recent pronounced SIE fluctuations occurring there. In the space of 3 years, the SIE sank from its highest value ever reached in September 2014 to record low in February 2017. In this work, a set of six state-of-the-art global climate models is used to evaluate the potential predictability of the Antarctic sea ice at such timescales. This first multi-model study of Antarctic sea ice predictability reveals that the ice edge location can potentially be predicted up to 3 years in advance. However, the ice edge location predictability shows contrasted seasonal performances, with high predictability in winter and no predictability in summer. The reemergence of the predictability from one winter to next is provided by the ocean through its large thermal inertia. Sea surface heat anomalies are stored at depth at the end of the winter and influences the sea ice advance the following year as they resurface. The effectiveness of this mechanism across models is found to depend upon the depth of the mixed layer. One should be very cautious about these potential predictability estimates as there is evidence that the Antarctic sea ice predictability is promoted by deep Southern Ocean convection. We therefore suspect models with excessive convection to show higher sea ice potential predictability results due to an incorrect representation of the Southern Ocean