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Ringed seals like meltwater plumes

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Alistair Everett is a Research Scientist at the Norwegian Polar Institute interested in ice-ocean interactions at marine-terminating glaciers. Here he describes recent research as part of the TIGRIF project, which seeks to understand the influence of tidewater glaciers on fjord dynamics and marine ecosystems, with particular focus on how these fjords may change in future when the glaciers retreat onto land.

In a recently published study (Everett et al. 2018), we investigated the water properties close to a glacier terminus in Kongsfjorden, northwestern Svalbard using a unique dataset collected by ringed seals (Pusa hispida) instrumented with GPS-CTD-SRDLs in 2012. The dataset had already been used to look at seal behaviour and their response to variations in sea ice (Hamilton et al., 2016). But in this new study the focus was instead on glaciology and the meltwater plume that could be observed very close to the glacier terminus; a place where it remains otherwise very challenging to collect data with boats and conventional CTD instruments.

The SRDLs used in this study (glued onto the hair of the seals) collected over one thousand CTD profiles within our study area during a period of around four months, providing us with a valuable time-series of oceanographic data. We were particularly interested in a number of profiles that showed ‘spikes’ of low temperature and salinity at depths of up to 60 metres. In our study, we showed that these ‘spikes’ were caused by the seals entering plumes of meltwater released from underneath the glacier. This was supported by running a clustering algorithm on the GPS locations returned by the SRDLs, which showed that the seals focused their foraging in plume locations, particularly during periods of high meltwater runoff from the glacier.

The data collected by the seals in Kongsfjorden provide important insights into a region where it has previously been very difficult to collect data. The results highlight the importance of plumes and marine-terminating glaciers for the ecosystems in these fjords. Further measurements within plumes can help us to constrain the volume of subglacial discharge, the associated melt rates and the influence on fjord circulation. In the future, as these glaciers retreat onto land, the plumes will eventually disappear, leading to the loss of this important foraging area for ringed seals and changes to the upwelling and circulation patterns within these fjords.


References:

Everett, A., Kohler, J., Sundfjord, A., Kovacs, K.M., Torsvik, T., Pramanik, A., Boehme, L., Lydersen, C., 2018. Subglacial discharge plume behaviour revealed by CTD-instrumented ringed seals. Sci. Rep. 8 (1), https://doi.org/10.1038/s41598-018-31875-8.

Hamilton, C. D., Lydersen, C., Ims, R. A. & Kovacs, K. M. 2016. Coastal habitat use by ringed seals Pusa hispida following a regional sea-ice collapse: importance of glacial refugia in a changing Arctic. Mar. Ecol. Prog. Ser. 545, 261–277, https://doi.org/10.3354/meps11598.    

Amundsen Sea data and Northern Seas data released in the public domain

A new release of the MEOP-CTD database is available publicly (version MEOP-CTD_2018-04-10) that now includes :

  • the deployment ct104 (M. Fedak, SMRU), obtained as part of the iSTAR A Programme (PI: K. Heywood, UEA)


  • A large number of deployments on hooded seals and harbour seals carried outover the previous decade by researchers at the Norwegian Polar Institute (PI: Kit Kovacs and Christian Lydersen).

Note also that the list of publication has been updated with more than 10 publications in 2017 and already 5 publications in 2018.

New release of the MEOP-CTD database

A new release of the MEOP-CTD database is now available. In this new release, about 80 CTD-SRDL tags have been added.

The data processing has been improved, with in particular two additional steps ensuring a better accuracy of salinity data:

  • A thermal cell effect correction has been applied on the entire database. Details of the method can be found in the following submitted manuscript:
    Mensah, V., Roquet, F., Picard, B., Pauthenet, E., Guinet, C., 2017.  A correction methodology for the thermal mass induced-errors of CTD tags mounted on marine mammals. In review in the Journal of Atmospheric and Oceanic Technologies. [PDF]
  • A density inversion removal algorithm is also applied, which seeks the minimum adjustment on the salinity profile to achieve neutral stability. The method is described in: Barker, P. M. and McDougall, T. J., 2017. Stabilizing Hydrographic Profiles with Minimal Change to the Water Masses. Journal of Atmospheric and Oceanic Technology, 34:1935-1945. doi: 10.1175/JTECH-D-16-0111.1

New data formats are also proposed, which hopefully will facilitate the use of our database by the largest number. In particular, a netCDF file version of data with profiles interpolated on a regular vertical grid is now available. Furthermore, the csv format is now proposed on a regular vertical grid as well.

If you want to learn more about the MEOP consortium, please read the recently published paper “Marine Mammals Exploring the Oceans Pole to Pole: A Review of the MEOP consortium” by Anne Treasure et al. published in Oceanography.

And don’t hesitate to send us feedbacks on your use of the MEOP-CTD database !!

Finally, you can follow the MEOP project on ResearchGate if you want to be the first to hear about the latest news.

Fabien and the MEOP consortium

The MEOP review is out in Oceanography

I am pleased to announce the publication of "Marine Mammals Exploring the Oceans Pole to Pole: A Review of the MEOP Consortium" by Anne Treasure et al. Marine Mammals Exploring the Oceans Pole to Pole: A Review o...

Another short note gives an overview of the current state of ocean observations using tagged animals: Ocean Observations Using Tagged Animals by Roquet et al.

These papers are part of the Special Issue on Autonomous and Lagrangian Platforms and Sensors (ALPS) in Oceanography, following the meeting ALPS (https://alps-ocean.us/) that took place in San Diego last February and was aimed at developing a broad vision for ALPS technology, capabilities, infrastructure, and user base in the next decade, and in the coming decades.

Note that this special issue also include the following papers on new exciting technologies of great potential for bio-logging:

      Do Southern Elephant Seals Behave Like Weather Buoys? by Cazau et al.

      A New Technology for Continuous Long-Range Tracking of Fish  by Rossby et al.

Antarctic predators unravel the mysteries of the Weddell Sea

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Sara Labrousse is Doctor in Marine and Antarctic Science interested in the foraging ecology of southern elephant seals (Mirounga leonina) in relation to physiography, hydrological factors, and sea ice condition. She tells us here about her recent experience in the Weddell Sea, where she deployed CTD-SRDL tags on Weddell seals as part of an oceanographic cruise led by Jean-Baptiste Sallée (CNRS researcher at LOCEAN in Paris) on board the R/V James Clark Ross.  [French link: http://phoques-antarctique-wapiti-2017.blogspot.se/]  


In January-March 2017, I was involved in an oceanographic cruise led by Jean-Baptiste Sallée (CNRS researcher at LOCEAN in Paris) in the Weddell Sea aboard the British Antarctic Survey vessel, the James Clark Ross. 

The Weddell Sea is a unique region responsible for 50 - 70% of the formation of deep water in Antarctica, motor of the global thermohaline circulation regulating the Earth's climate. The Weddell Sea also harbors rich ecosystems associated with the seasonal sea ice dynamics (krill, copepods, fish, birds and marine mammals). However, this sector remains under-sampled and little is known about the oceanographic and biological processes taking place in this region due to compact and extended sea ice making the access difficult even in summer. The cruise represented a unique opportunity to study the ecology of marine top predators by equipping them with satellite-relayed data loggers, in a region where little is known on their movements, foraging activity and their preferences in terms of oceanographic conditions.    

The cruise was part of the WAPITI project (Water-mass transformation and Pathways In The Weddell Sea: uncovering the dynamics of a global climate chokepoint from In-situ measurements) funded by the European Research Council (ERC). WAPITI aims to understand how and where water-masses are pre-conditioned and transported on the Antarctic shelf, before coming into contact with the ice shelves: an highly sensitive process ultimately controlling the rate of melt of the Earth’s largest ice reservoir. Associated with this cruise, we did opportunistic deployment from the R/V James Clark Ross of five Argos tags coupled with diving recorder and a CTD miniaturized sensor on one emblematic specie of pinnipeds, major consumer of the ecosystem of the Antarctic sea ice the Weddell seals (Leptonychotes weddellii). 

Such deployment coordinated within the framework of the physics-based WAPTITI will allow unique interdisciplinary research: (i) acquiring essential information on the feeding ecology of Antarctic seals, where only few studies are available, and (ii) acquiring a vast amount of information on the regional water-mass seasonal cycle and circulation acquired from instruments deployed as part of the WAPITI project, and valuable hydrological data under sea ice in late summer, autumn and winter from the CTD profiles recorded during dives of this predator. The study of the seal diving behavior under sea ice combined with simultaneously recorded hydrographic profiles will first highlight preferred feeding habitat in terms of oceanographic conditions. Secondly, this telemetry monitoring will help to quantify the role of hydrological and sea ice conditions on the abundance and availability of resources in the peri-Antarctic shelf, improving our still very patchy knowledge on ecosystem functioning under winter sea ice. 

Acknowledgements: Jean-Baptiste Sallée (ERC), Jean-Benoit Charrassin (CNES), Clive McMahon & Robert Harcourt (IMOS), and all the WAPITI TEAM;

The MEOP-CTD database in ODV has been updated

The updated version of the MEOP-CTD database is now available in Ocean Data View as a ready-to-use data collection, thanks to Reiner Schlitzer (AWI, Germany):

https://odv.awi.de/en/data/ocean/meop_ctd_marine_mammals_database/

Use ODV to explore MEOP-CTD data, easily plotting the data profiles, property sections and making beautiful horizontal maps with the DIVA gridding software.

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Antarctic bottom water formation in Prydz Bay

Research published today in Nature Communications (Williams et al. 2016), and supported through the Australian Antarctic Program, has demonstrated that fresh water from Antarctic’s melting ice shelves slows the processes responsible for the formation of deep-water ocean currents that regulate global temperatures.

A fourth production region for the globally important Antarctic bottom water has been attributed to dense shelf water formation in the Cape Darnley Polynya, adjoining Prydz Bay in East Antarctica. Here we show new observations from CTD-instrumented elephant seals in 2011–2013 that provide the first complete assessment of dense shelf water formation in Prydz Bay. After a complex evolution involving opposing contributions from three polynyas (positive) and two ice shelves (negative), dense shelf water (salinity 34.65–34.7) is exported through Prydz Channel. This provides a distinct, relatively fresh contribution to Cape Darnley bottom water. Elsewhere, dense water formation is hindered by the freshwater input from the Amery and West Ice Shelves into the Prydz Bay Gyre. This study highlights the susceptibility of Antarctic bottom water to increased freshwater input from the enhanced melting of ice shelves, and ultimately the potential collapse of Antarctic bottom water formation in a warming climate. 

The evolution of Prydz Bay’s dense shelf water contribution to Cape Darnley bottom water. 

   

Release of MEOP-CTD_2016-07-12

Already one year that the MEOP portal has been launched!

A very successful year for our growing community… in one year, 23 new publications using MEOP data have been added, increasing the number of MEOP-related peer-reviewed publications to 94. Simultaneously, the MEOP-CTD database has been included in major oceanographic data centres, including the NODC, Coriolis, and the BODC. More than 100 individual users have requested the database using the MEOP web interface.

It is now time to release a major update of the MEOP-CTD database. In this new version, namely the MEOP-CTD_2016-07-12, more animal-borne instrument data are included. The number of profile publicly distributed has increased from slightly less than 300,000 to almost 400,000 profiles. Also, 125,000 other profiles are included into the database, although they remain private, i.e. accessible only upon request. In total, the database has now reached the 500,000 profiles milestone.

Two datasets have been added in particular, that expand considerably the spatial coverage of the MEOP-CTD database. The first consists of 30,000+ profiles in the northeastern sector of the North Pacific, obtained by instrumenting Northern Elephant Seals in California (D. Costa, University of Santa Cruz, USA group). The second dataset provides 70,000+ temperature-only profiles in the Labrador Sea/Irminger Sea and in Baffin Bay/Hudson Bay/Gulf of St Lawrence shelf areas (see e.g. Straneo et al. 2010, Grist et al. 2011, 2014) from Hooded and Ringed seals (G. Stenson, DFO, Canada group).

Finally, a new stream of data has been added, obtained from TDR (time-depth recorder) attached to elephant seals in the Kerguelen area (PI: C. Guinet, CEBC, French group). The MEOP-TDR database includes 285,000 temperature profiles obtained from 69 different loggers. This dataset has a very high spatial and temporal resolution, with 60-100 profiles per day (i.e. ~4 profiles/hour), allowing to observe mesoscale ocean activity.

To facilitate the access to our database, we have developed Matlab tools and Python tools to read and manipulate files with the netCDF format. Note also that this format can be easily read by the software Ocean Data View. For those not comfortable with the netCDF format, a csv format is also available.

Please continue using our data, and support us by providing us your feedbacks, citing our work and spreading the word around you.

Unraveling the circulation and melwater distribution in the Bellingshausen Sea

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Xiyue Zhang in a mountain trek

Xiyue (Sally) Zhang is a PhD student in Environmental Science and Engineering at the California Institute of Technology. She here reporting on some exciting science recently published in the Geophysical Research Letters.


The polar regions have long been fascinating to me, not only for their exoticness, but also their importance to the global climate. My thesis focuses on polar cloud dynamics, and I also worked closely with oceanographers at Caltech to enhance our understanding of ocean/ice shelf interactions in Antarctica.

We started by exploring data from 13 seals that were tagged in 2010. A couple of seals traveled all the way from the tip of the Antarctic Peninsula to the western Bellingshausen Sea shelf break. What really inspired us to focus on the Bellingshausen Sea is the observational study that showed high ice shelf basal melt rates in the region. Therefore, we decided to use all available data in the MEOP consortium in the Bellingshausen Sea (Figure 1). The seal-borne data are advantageous over the limited cruise-based measurements due to the inaccessible nature of the region: it is geographically hard to reach, and hampered by seasonal sea ice cover.


Figure 1: The Bellingshausen Sea region with dots showing the MEOP profiles. Contours show bottom bathymetry. The big black box highlights the main canyon Belgica Trough (BT). For more information, see Zhang et al. (2016).

Using the temperature, salinity, and pressure data collected by 80 seals in the Bellingshausen Sea region from 2007 to 2014, Zhang et al. 2016 analyzed the three-dimensional water masses distribution at the continental shelf break and on the shelf. The Bellingshausen Sea hosts 6 ice shelves that have thinned rapidly over recent decades. A cyclonic circulation within the Belgica Trough, the main shelf canyon, is identified based on the meltwater distribution. This circulation brings water at least 3 degrees Celsius warmer than the freezing temperature towards the coast on the eastern boundary. Water is modified to be colder and fresher as it exits the Belgica Trough via the western boundary. Furthermore, a westward slope current is implied west of the trough. Our findings support the high basal melt rate and thinning of ice shelves in the region detected by satellite observations. We plan to continue using data from the MEOP consortium to improve our understanding of shelf circulation in Antarctica.    

Find out more in the press, on The Washington Post and (in German) in the Klimaretter.

Fieldwork at Davis Station, Antarctica

This year the Integrated Marine Observing system (IMOS) Animal Tracking facility again sent a team of three researchers to Davis Station in Antarctica for the southern summer to partner with some unlikely research collaborators - southern elephant seals. Sophisticated Conductivity-Temperature-Depth (CTD) relay loggers were attached to the seals to collect ocean profiles from south of 60 degrees South.

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Doctors Clive McMahon, Esther Tarszisz and Louise McMahon, all from the Sydney Institute of Marine Science, teamed up to build on ten years of ocean sampling by the Australian and French Antarctic Programs and IMOS between Iles Kerguelen and Prydz Bay. The CTD profiles that are currently being beamed back to us via the ARGOS satellite system build on the time-series of high-resolution oceanographic data that looks at annual variation in ocean structure and the formation of the globally important Antarctic Bottom Water. 

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This year the teams at Davis and at Kerguelen managed to get 16 instruments out on southern elephant seals all of which are sending back crucial information on ocean structure of particularly interest is the information being collected in the Barrier and Amundsen Polynyas that will help us build a better picture of dense water formation in the Antarctic. Dense water is the precursor of Antarctic Bottom Water that drives the Southern Ocean component of the ‘global ocean conveyor belt’, a constantly moving system of deep-ocean circulation driven by temperature and salinity. 

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Being part of this globally importnat project is not only scientifically stimulating but, also personally rewarding – after all how fantastic to spend a summer in the Antarctic surrounded by seals, penguins and scenery that is simply stunning.

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The team returned in March and while it still seems like a long way off preparations are in full swing for the upcoming season which include; ordering and shipping equipment, recruiting field staff and of course the all important grant and proposal writing.


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