Browsing by Subject "Sea ice"

Now showing 1 - 3 of 3
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    Open Access
    Antarctic climate change: extreme events disrupt plastic phenotypic response in Adélie penguins
    (Public Library of Science, 2014) Lescroël, Amélie; Ballard, Grant; Grémillet, David; Authier, Matthieu; Ainley, David G
    In the context of predicted alteration of sea ice cover and increased frequency of extreme events, it is especially timely to investigate plasticity within Antarctic species responding to a key environmental aspect of their ecology: sea ice variability. Using 13 years of longitudinal data, we investigated the effect of sea ice concentration (SIC) on the foraging efficiency of Adélie penguins ( Pygoscelis adeliae ) breeding in the Ross Sea. A 'natural experiment' brought by the exceptional presence of giant icebergs during 5 consecutive years provided unprecedented habitat variation for testing the effects of extreme events on the relationship between SIC and foraging efficiency in this sea-ice dependent species. Significant levels of phenotypic plasticity were evident in response to changes in SIC in normal environmental conditions. Maximum foraging efficiency occurred at relatively low SIC, peaking at 6.1% and decreasing with higher SIC. The 'natural experiment' uncoupled efficiency levels from SIC variations. Our study suggests that lower summer SIC than currently observed would benefit the foraging performance of Adélie penguins in their southernmost breeding area. Importantly, it also provides evidence that extreme climatic events can disrupt response plasticity in a wild seabird population. This questions the predictive power of relationships built on past observations, when not only the average climatic conditions are changing but the frequency of extreme climatic anomalies is also on the rise.
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    SHARC Buoy: Robust firmware design for a novel, low-cost autonomous platform for the Antarctic Marginal Ice Zone in the Southern Ocean
    (2021) Jacobson, Jamie Nicholas; Verrinder, Robyn; Mishra, Amit; Vichi, Marcello
    Sea ice in the Antarctic Marginal Ice Zone (MIZ) plays a pivotal role in regulating heat and energy exchange between oceanic and atmospheric systems, which drive global climate. Current understanding of Southern Ocean sea ice dynamics is poor with temporal and spatial gaps in critical seasonal data-sets. The lack of in situ environmental and wave data from the MIZ in the Antarctic region drove the development of UCT's first generation of in situ ice-tethered measurement platform as part of a larger UCT and NRF SANAP project on realistic modelling of the Marginal Ice Zone in the changing Southern Ocean (MISO). This thesis focuses on the firmware development for the device and the design process taken to obtain key measurements for understanding sea ice dynamics and increasing sensing capabilities in the Southern Ocean. The buoy was required to survive the Antarctic climate and contained a global positioning system, temperature sensor, digital barometer and inertial measurement unit to measure waves-in-ice. Power was supplied to the device by a power supply unit consisting of commercial-grade batteries in series with a temperature-resistant low dropout regulator, and a power sensor to monitor the module. A satellite modem transmitted data through the Iridium satellite network. Finally, Flash chips provided permanent data storage. Firmware and peripheral driver files were written in C for an STMicroelectronics STM32L4 Arm-based microcontroller. To optimise the firmware for low power consumption, inactive sensors were placed in power-saving mode and the processor was put to sleep during periods of no sampling activity. The first device deployment took place during the SCALE winter expedition in July 2019. Two devices were deployed on ice floes to test their performance in remote conditions. However, due to mechanical and power errors, the devices failed shortly after deployment. A third device was placed on the deck of SA Aghulas II during the expedition and successfully survived for one week while continuously transmitting GPS coordinates and ambient temperature. The second generation featured subsequent improvements to the mechanical robustness and sensing capabilities of the device. However, due to the 2020 COVID-19 pandemic, subsequent Antarctic expeditions were cancelled resulting in the final platform evaluation taking place on land. The device demonstrates a proof of concept for a low-cost, ice-tethered autonomous sensing device. However, additional improvements are required to overcome severe bandwidth and power constraints.
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    Where to forage in the absence of sea ice? Bathymetry as a key factor for an arctic seabird
    (Public Library of Science, 2016) Amélineau, Françoise; Grémillet, David; Bonnet, Delphine; Le Bot, Tangi; Fort, Jérôme
    The earth is warming at an alarming rate, especially in the Arctic, where a marked decline in sea ice cover may have far-ranging consequences for endemic species. Little auks, endemic Arctic seabirds, are key bioindicators as they forage in the marginal ice zone and feed preferentially on lipid-rich Arctic copepods and ice-associated amphipods sensitive to the consequences of global warming. We tested how little auks cope with an ice-free foraging environment during the breeding season. To this end, we took advantage of natural variation in sea ice concentration along the east coast of Greenland. We compared foraging and diving behaviour, chick diet and growth and adult body condition between two years, in the presence versus nearby absence of sea ice in the vicinity of their breeding site. Moreover, we sampled zooplankton at sea when sea ice was absent to evaluate prey location and little auk dietary preferences. Little auks foraged in the same areas both years, irrespective of sea ice presence/concentration, and targeted the shelf break and the continental shelf. We confirmed that breeding little auks showed a clear preference for larger copepod species to feed their chick, but caught smaller copepods and nearly no ice-associated amphipod when sea ice was absent. Nevertheless, these dietary changes had no impact on chick growth and adult body condition. Our findings demonstrate the importance of bathymetry for profitable little auk foraging, whatever the sea-ice conditions. Our investigations, along with recent studies, also confirm more flexibility than previously predicted for this key species in a warming Arctic.