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28.12.2024 - 01.02.2025 Cape Town - Antarctica - Cape Town M/V Silver Mary
No full textThe TrollTransect2025 cruise (TT25) was the annual cargo supply mission to Troll Station, Antarctica. The cruise was conducted aboard the M/V Silver Mary, travelling from Cape Town to the Antarctic ice shelf edge near 70°S, 3°E carrying equipment and supplies for the research station. The ship left Cape Town on December 28, 2024 and returned to the same port on February 1, 2025.
Since 2020, the Norwegian Polar Institute (NPI) has taken advantage of the opportunity given by annual cargo missions to Troll research station to conduct a program of scientific observations in order to better understand the most important physical, biogeochemical and biological processes in King Haakon VII Sea of the Southern Ocean. The cruise objectives alternate every other year; for the TT25 cruise, priorities included the turnover of the three Multidisciplinary Ocean Moored Observatory DML ocean moorings on the Antarctic shelf break and multidisciplinary hydrographic surveying across the continental slope.
This report details the scientific part of the cruise.publishedVersio
Fur lice in Arctic foxes in Svalbard: prevalence, intensity and impacts on health status and demographics
Full text linkIn November 2019, bloodsucking lice were identified in Arctic foxes in Svalbard for the first time, coinciding with similar findings in Nunavut, Canada. Genetic analysis revealed that lice from both regions were 100 % identical, suggesting the presence of a previously undescribed species distinct from dog lice. The origin of the lice remains uncertain, but historical evidence of lice in Canadian Arctic foxes from the 1990’s supports the hypothesis that they may have been introduced to Svalbard by migrating Arctic foxes.
The prevalence of lice in Arctic foxes in Svalbard has increased since the 2019–2020 trapping season, initially affecting an estimated 10 % of the population and rising to 76 % in the 2021–2022 season. Morphological and molecular analyses, along with observations of abnormal fur loss patterns in infested foxes, highlight the impact of lice infestations. These species-specific ectoparasites, which are highly dependent on their hosts, cause pruritis and fur damage, and in severe cases, can lead to anaemia.
The study aimed to collect all Arctic fox carcasses trapped during the 2022–2023 season to investigate the impact of fur lice by documenting the prevalence, abundance, and distribution of lice, changes in fur quality and skin pathology, and develop and establish methods and protocols for the evaluation of the intensity of lice infestation. The project also conducted a pilot study to test camera traps on Arctic fox den sites to provide a non-invasive method for monitoring lice infections.
During the 2022–2023 trapping season, a total of 36 Arctic foxes were captured, with fur lice detected in 16 individuals, resulting in an overall prevalence of 41.7 %. This was a decline from the previous year’s prevalence of 76 % but remains higher than earlier seasons. Lice were mainly found in the neck and shoulder areas but were distributed across the entire body in heavily infested foxes. Heavier lice burdens in the pelts were related to lower body weights. Infestations were associated with significant fur damage, including discoloration and shortened fur, with infected foxes showing these changes more frequently than uninfected ones. The total lice burden ranged from 0 to 10 984 per pelt, with an average of 3 161. Egg density was higher than other life stages (eggs, larvae and adults), and the highest lice concentrations were found in the neck and shoulders. Histopathological analysis of the skin showed chronic irritation caused by lice, though there was no evidence of inflammation or immune response. Hair follicles appeared healthy and undamaged and hair loss was attributed to mechanical damage from scratching and biting, driven by tactile irritation rather than hypersensitivity.
Camera traps at five breeding dens captured over 24 000 images, with 409 showing Arctic foxes. Signs of lice infestation were evident in 279 of these images, documenting infestation at all dens. Infestation severity developed throughout the season (from January–February) and peaked in late spring (May–June). Despite this, foxes with no sign of lice on the fur were also observed on the dens. The observed seasonal trend in louse infections is noteworthy. Although the trapped fox dataset did not show a clear correlation between infection intensity and trapping dates, the trapping ends in mid-March, well before the peak seasonal changes observed in May and June through camera trap evidence. Thus, prevalence and abundance estimates based on trapped foxes may underestimate the impact of lice on the population.
Based on these findings and the literature we hypothesize that the recent introduction of fur lice to Arctic foxes in Svalbard, a previously naïve population, may lead to a gradual development of partial immunity. Over time, younger naive individuals or older foxes with weakened immune systems may become more susceptible to heavy infestations compared to healthy adults with prior exposure to lice. Immunity could also explain why some uninfected foxes coexist with infected individuals at the same breeding dens despite close physical contact. Another aspect related to the seasonal molt is the finding that seasonal shedding of winter fur in spring in other species significantly reduces louse infection intensity. Similarly, the seasonal molt of Arctic foxes from dense winter fur to summer fur in May probably plays a role in reducing louse prevalence and abundance. Hairs with attached eggs are shed during molting, decreasing the overall infection burden. So far, we have no information about fur lice in Arctic foxes during summer. Continued monitoring is recommended to better understand the dynamics of lice infestations, their health impacts, and potential development of immunity in the Arctic fox population.publishedVersio
Formation and fate of freshwater on an ice floe in the Central Arctic
Full text linkThe melt of snow and sea ice during the Arctic summer is a significant source of relatively fresh meltwater. The fate of this freshwater, whether in surface melt ponds or thin layers underneath the ice and in leads, impacts atmosphere–ice–ocean interactions and their subsequent coupled evolution. Here, we combine analyses of datasets from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition (June–July 2020) for a process study on the formation and fate of sea ice freshwater on ice floes in the Central Arctic. Our freshwater budget analyses suggest that a relatively high fraction (58 %) is derived from surface melt. Additionally, the contribution from stored precipitation (snowmelt) outweighs by 5 times the input from in situ summer precipitation (rain). The magnitude and rate of local meltwater production are remarkably similar to those observed on the prior Surface Heat Budget of the Arctic Ocean (SHEBA) campaign, where the cumulative summer freshwater production totaled around 1 m during both. A relatively small fraction (10 %) of freshwater from melt remains in ponds, which is higher on more deformed second-year ice (SYI) compared to first-year ice (FYI) later in the summer. Most meltwater drains laterally and vertically, with vertical drainage enabling storage of freshwater internally in the ice by freshening brine channels. In the upper ocean, freshwater can accumulate in transient meltwater layers on the order of 0.1 to 1 m thick in leads and under the ice. The presence of such layers substantially impacts the coupled system by reducing bottom melt and allowing false bottom growth; reducing heat, nutrient, and gas exchange; and influencing ecosystem productivity. Regardless, the majority fraction of freshwater from melt is inferred to be ultimately incorporated into the upper ocean (75 %) or stored internally in the ice (14 %). Terms such as the annual sea ice freshwater production and meltwater storage in ponds could be used in future work as diagnostics for global climate and process models. For example, the range of values from the CESM2 climate model roughly encapsulate the observed total freshwater production, while storage in melt ponds is underestimated by about 50 %, suggesting pond drainage terms as a key process for investigation.publishedVersio
Enhanced basal melting in winter and spring: seasonal ice–ocean interactions at the Ekström Ice Shelf, East Antarctica
Full text linkBasal melting of Antarctic ice shelves significantly contributes to ice sheet mass loss, with distinct regional disparities in melt rates driven by ocean properties. In Dronning Maud Land (DML), East Antarctica, cold water predominantly fills the ice shelf cavities, resulting in generally low annual melt rates. In this study, we present a 4-year record of basal melt rates at the Ekström Ice Shelf, measured using an autonomous phase-sensitive radio-echo sounder (ApRES). Observations reveal a low mean annual melt rate of 0.44 m a−1, with a seasonal variability. Enhanced melting occurs in winter and spring, peaking at over 1 m a−1, while rates are decreased in summer and autumn. We hypothesise that the dense water formed during sea-ice formation erodes the water column stratification during late winter and spring, leading to an increase in the buoyancy of the ice shelf water plume. An idealised plume model supports this hypothesis, indicating that the plume velocity is the primary driver of seasonal basal melt rate variability, while changes in ambient water temperature play a secondary role in the range of oceanographic conditions that are observed below the Ekström Ice Shelf. These findings offer new insights into the dynamics of ice–ocean interactions in East Antarctica, emphasising the need for further observations to refine our understanding of ocean variability within ice shelf cavities and improve assessments of ice shelf mass balance
