A Weddell seal with a CTD tag attached on the head. Credit: Nobuo Kokubun (NIPR).
Oceanographers have terrific problem carrying out examinations by ship in Antarctic continental shelf areas where ice is connected to the coast, so a team of scientists has changed these boat-based research studies with sensors connected to seals, which have far less trouble navigating such waters.
A research study describing the animal-born examination method and the scientists findings were released in the journal Limnology and Oceanography.
The continental shelves of Antarctica are one of the most biologically efficient areas in the worlds oceans as a result of the big amount of nutrients produced by interactions between ocean, sea ice and ice shelf. In East Antarctica, strong katabatic wind enhances sea ice production in the coastal polynyas, areas of open, unfrozen seawater surrounded by sea ice. Outside the polynyas, sometime substantial sea ice connected to the shore (referred to as landfast ice) exists where a great deal of predators such as Weddell seals and emperor penguins inhabit.
The colored arrows show the cross-shelf water inflow, and the white block arrows reveal the possible trophic energy flow. Utilizing the transmitted data from the instrumented seals, the researchers discovered that low and warm salinity water appeared in the subsurface during fall, and the depth of the warm water became deeper as the season advanced. By integrating with meteorological and oceanographic modelling, the researchers revealed that seasonally dominating easterly wind during fall causes a circulation of off-shelf surface area warm waters as well as potentially additional victim onto the continental shelf. At the same time recorded seals diving information indicated that the low and warm salinity water had positive results on the seals foraging behaviour. Now that this has actually been demonstrated, the team wants to go even more and approximate the quantity of water and prey being transported onto the shelves by this wind- driven procedure.
These ocean, sea-ice and ice-shelf water exchanges– especially those between deep warm waters originating from off-shelf areas, sea-ice zones that alter with the season, and coastal polynyas– play important functions in biological production throughout continental rack locations.
As a result of the significant seasonal and regional variation of such cross-shelf flows of water, much more information explaining how both surface area and deep waters from close-by off-shelf areas intrude onto the rack and blend with local waters is necessary for a deeper understanding of biological production here.
But due to the difficulty of conducting oceanographic observations by ship in continental shelf locations covered by landfast ice, these cross-shelf water exchanges and their seasonal variations are not well comprehended.
Schematic summary of autumn/early winter oceanographic and following biological conditions on the continental rack exposed by the study. The colored arrows reveal the cross-shelf water inflow, and the white block arrows show the possible trophic energy circulation. Water masses are abbreviated as follows and shown by different colors. mCDW: Modified Circumpolar Deep Water (Warm and high salinity), WW: Winter Water (Cold and low salinity), AASW: Antarctic Surface Water (Warm and low salinity). Credit: Illustration by Shinichiro Kinoshita.
In the last few years, scientists have started to release oceanographic information logging devices to marine animals, in specific equipment that tape-records conductivity, depth and temperature level (CTD). The CTD information are fundamental to determine the ocean waters qualities through the entire water column, and they permit researchers to estimate the origin of water.
” Previous studies using instruments strapped to migrating southern elephant seals and resident Weddell seals– a deep diving predator– had shown some intriguing physical procedures in Antarctic areas,” stated Nobuo Kokubun, an assistant teacher with Japans National Institute of Polar Research and the lead author of the research study, “but even here, there has actually hardly been anything examining coastal locations covered by landfast ice.”.
The scientists carried out a field research study checking out the winter season oceanographic conditions and their biological repercussions in eastern Dronning Maud Land and western Enderby Land in East Antarctica by connecting CTD-Satellite Relay Data Loggers with glue to the heads of 8 Weddell seals in March to September of 2017. The loggers weighed about half a kg and were about the size of a small Rubiks Cube. The areas were closed for their comprehensive amount of landfast ice and absence of broad continental racks or unique seaside polynyas.
Using the transmitted data from the instrumented seals, the researchers discovered that low and warm salinity water appeared in the subsurface throughout autumn, and the depth of the warm water ended up being deeper as the season advanced. By combining with meteorological and oceanographic modelling, the scientists revealed that seasonally prevailing easterly wind during fall causes a flow of off-shelf surface warm waters along with potentially extra prey onto the continental shelf. In truth, all at once recorded seals diving data showed that the low and warm salinity water had positive results on the seals foraging behaviour. Overall, the scientists think about that the wind-driven physical procedure may boost victim availability in the Antarctic seaside marine ecosystem.
The investigation showed that seals with oceanographic sensors connected to them could be powerful tools to explore ecological and oceanographic conditions throughout a very wide variety of Antarctic continental shelves covered with landfast ice. Now that this has actually been demonstrated, the team wishes to go even more and estimate the amount of water and prey being transferred onto the racks by this wind- driven procedure. Eventually, the researchers intend to have the ability to use these information to forecast how the Antarctic seaside marine environment is reacting to the ongoing fast changes in Antarctic sea ice.
Recommendation: “Shoreward intrusion of oceanic surface waters changes physical and biological ocean structures on the Antarctic continental rack during winter season: Observations from instrumented seals” by Nobuo Kokubun, Yukiko Tanabe, Daisuke Hirano, Vigan Mensah, Takeshi Tamura, Shigeru Aoki and Akinori Takahashi, 12 September 2021, Limnology and Oceanography.DOI: 10.1002/ lno.11914.
About National Institute of Polar Research (NIPR).
As a member of the Research Organization of Information and Systems (ROIS), the NIPR provides scientists throughout Japan with facilities support for Arctic and Antarctic observations, strategies and executes Japans Antarctic observation jobs, and conducts Arctic researches of different clinical fields such as the atmosphere, ice sheets, the ecosystem, the upper environment, the aurora and the Earths magnetic field. In addition to the research study projects, the NIPR likewise arranges the Japanese Antarctic Research Expedition and manages data and samples acquired during such expeditions and tasks.
About the Research Organization of Information and Systems (ROIS).
The Research Organization of Information and Systems (ROIS) is a parent company of four national institutes (National Institute of Polar Research, National Institute of Informatics, the Institute of Statistical Mathematics and National Institute of Genetics) and the Joint Support-Center for Data Science Research. It is ROISs mission to promote integrated, cutting-edge research study that goes beyond the barriers of these institutions, in addition to facilitating their research activities, as members of inter-university research institutes.