scholarly journals Fatty acids and stable isotope signatures of first-year and multiyear sea ice in the Canadian High Arctic

Elem Sci Anth ◽  
2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Doreen Kohlbach ◽  
Steven W. Duerksen ◽  
Benjamin A. Lange ◽  
Joannie Charette ◽  
Anke Reppchen ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Sea Ice ◽  
Food Web ◽  
Relative Proportion ◽  
High Arctic ◽  
First Year ◽  
Biochemical Processes ◽  
Food Web Interactions ◽  
Stable Isotope Signatures ◽  
Critical Components

Ice algae are critical components to the lipid-driven Arctic marine food web, particularly early in the spring. As little is known about these communities in multiyear ice (MYI), we aimed to provide a baseline of fatty acid (FA) and stable isotope signatures of sea-ice communities in MYI from the Lincoln Sea and compare these biomarkers to first-year ice (FYI). Significant differences in the relative proportions of approximately 25% of the identified FAs and significantly higher nitrogen stable isotope values (δ15N) in bottom-ice samples of FYI (δ15N = 6.4 ± 0.7%) compared to MYI (δ15N = 5.0 ± 0.4%) reflect different community compositions in the two ice types. Yet, the relative proportion of diatom- and dinoflagellate-associated FAs, as well as their bulk and most of the FA-specific carbon stable isotope compositions (δ13C) were not significantly different between bottom FYI (bulk δ13C: –28.4% to –26.7%, FA average δ13C: –34.4% to –31.7%) and MYI (bulk δ13C: –27.6% to –27.2%, FA average δ13C: –33.6% to –31.9%), suggesting at least partly overlapping community structures and similar biochemical processes within the ice. Diatom-associated FAs contributed, on average, 28% and 25% to the total FA content of bottom FYI and MYI, respectively, indicating that diatoms play a central role in structuring sea-ice communities in the Lincoln Sea. The differences in FA signatures of FYI and MYI support the view that different ice types harbor different inhabitants and that the loss of Arctic MYI will impact complex food web interactions with ice-associated ecosystems. Comparable nutritional quality of FAs, however, as indicated by similar average levels of polyunsaturated FAs in bottom FYI (33%) and MYI (28%), could help to ensure growth and reproduction of ice-associated grazers despite the shift from a MYI to FYI-dominated sea-ice cover with ongoing climate warming.

scholarly journals Snow microstructure on sea ice: Importance for remote sensing applications

2021 ◽  
Author(s):  
Amy R. Macfarlane ◽  
Stefanie Arndt ◽  
Ruzica Dadic ◽  
Carolina Gabarró ◽  
Bonnie Light ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Sea Ice ◽  
Remote Sensing Data ◽  
High Arctic ◽  
First Year ◽  
Sensing Data ◽  
Snow Properties ◽  
Multiyear Ice ◽  
Snow Samples

<p>Snow plays a key role in interpreting satellite remote sensing data from both active and passive sensors in the high Arctic and therefore impacts retrieved sea ice variables from these systems ( e.g., sea ice extent, thickness and age). Because there is high spatial and temporal variability in snow properties, this porous layer adds uncertainty to the interpretation of signals from spaceborne optical sensors, microwave radiometers, and radars (scatterometers, SAR, altimeters). We therefore need to improve our understanding of physical snow properties, including the snow specific surface area, snow wetness and the stratigraphy of the snowpack on different ages of sea ice in the high Arctic.</p><p>The MOSAiC expedition provided a unique opportunity to deploy equivalent remote sensing sensors in-situ on the sea ice similar to those mounted on satellite platforms. To aid in the interpretation of the in situ remote sensing data collected, we used a micro computed tomography (micro-CT) device. This instrument was installed on board the Polarstern and was used to evaluate geometric and physical snow properties of in-situ snow samples.  This allowed us to relate the snow samples directly to the data from the remote sensing instruments, with the goal of improving interpretation of satellite retrievals. Our data covers the full annual evolution of the snow cover properties on multiple ice types and ice topographies including level first-year (FYI), level multi-year ice (MYI) and ridges.</p><p>First analysis of the data reveals possible uncertainties in the retrieved remote sensing data products related to previously unknown seasonal processes in the snowpack. For example, the refrozen porous summer ice surface, known as surface scattering layer, caused the formation of a hard layer at the multiyear ice/snow interface in the winter months, leading to significant differences in the snow stratigraphy and remote sensing signals from first-year ice, which has not experienced summer melt, and multiyear ice. Furthermore, liquid water dominates the extreme coarsening of snow grains in the summer months and in winter the temporally large temperature gradients caused strong metamorphism, leading to brine inclusions in the snowpack and large depth hoar structures, all this significantly influences the signal response of remote sensing instruments.</p>

scholarly journals Indirect food web interactions mediated by predator–rodent dynamics: relative roles of lemmings and voles

2013 ◽  
Vol 9 (6) ◽  
pp. 20130802 ◽  
Author(s):  
Rolf A. Ims ◽  
John-André Henden ◽  
Anders V. Thingnes ◽  
Siw T. Killengreen
Keyword(s):  
Food Web ◽  
Predictive Ability ◽  
Population Cycles ◽  
High Arctic ◽  
Food Web Interactions ◽  
Production Cycles ◽  
Low Arctic ◽  
Vole Species ◽  
Rodent Community ◽  
Predation Rates

Production cycles in birds are proposed as prime cases of indirect interactions in food webs. They are thought to be driven by predators switching from rodents to bird nests in the crash phase of rodent population cycles. Although rodent cycles are geographically widespread and found in different rodent taxa, bird production cycles appear to be most profound in the high Arctic where lemmings dominate. We hypothesized that this may be due to arctic lemmings inducing stronger predator responses than boreal voles. We tested this hypothesis by estimating predation rates in dummy bird nests during a rodent cycle in low-Arctic tundra. Here, the rodent community consists of a spatially variable mix of one lemming ( Lemmus lemmus ) and two vole species ( Myodes rufocanus and Microtus oeconomus ) with similar abundances. In consistence with our hypothesis, lemming peak abundances predicted well crash-phase nest predation rates, whereas the vole abundances had no predictive ability. Corvids were found to be the most important nest predators. Lemmings appear to be accessible to the whole predator community which makes them particularly powerful drivers of food web dynamics.

scholarly journals Growth Rate and Salinity Profile of First-Year Sea Ice in the High Arctic

1981 ◽  
Vol 27 (96) ◽  
pp. 315-330 ◽  
Author(s):  
M. Nakawo ◽  
N. K Sinha
Keyword(s):  
Growth Rate ◽  
Sea Ice ◽  
Physical Properties ◽  
High Arctic ◽  
First Year ◽  
Baffin Island ◽  
Growth Season ◽  
Method Of Calculation ◽  
Salinity Profile ◽  
Snow Conditions

AbstractThis paper describes the growth of sea ice and the salinity profiles observed in Eclipse Sound near Pond Inlet, Baffin Island, Canada, during the winter of 1977–78. A numerical method of calculation has been developed to incorporate the variations in snow conditions and physical properties of ice and snow during the growth season. It is shown that the growth rate can be predicted reasonably well. It is also shown that the vertical salinity profile in the ice towards the end of the season, provides a record of previous climatological conditions. A dependence has been shown between the predicted growth rate and the measured salinity.

scholarly journals Net heterotrophy in High Arctic first-year and multi-year spring sea ice

Elem Sci Anth ◽  
2022 ◽  
Vol 10 (1) ◽  
Author(s):  
Karley Campbell ◽  
B. A. Lange ◽  
J. C. Landy ◽  
C. Katlein ◽  
M. Nicolaus ◽  
...  
Keyword(s):  
Species Composition ◽  
Sea Ice ◽  
High Arctic ◽  
Algal Community ◽  
First Year ◽  
Light Conditions ◽  
Mixed Composition ◽  
Sampling Campaign ◽  
Variable Light ◽  
Ice Floes

The net productivity of sea ice is determined by the physical and geochemical characteristics of the ice–ocean system and the activity of organisms inhabiting the ice. Differences in habitat suitability between first-year and multi-year sea ice can affect the ice algal community composition and acclimation state, introducing considerable variability to primary production within each ice type. In this study, we characterized the biogeochemical variability between adjacent first-year and multi-year sea ice floes in the Lincoln Sea of the Canadian High Arctic, during the May 2018 Multidisciplinary Arctic Program—Last Ice sampling campaign. Combining measurements of transmitted irradiance from a remotely operated underwater vehicle with laboratory-based oxygen optode incubations, this work shows widespread heterotrophy (net oxygen uptake) in the bottom 10 cm of both ice types, particularly in thick multi-year ice (>2.4 m) and early morning of the 24-h day. Algal acclimation state and species composition varied between ice types despite similar net community production due to widespread light and nutrient limitation. The first-year ice algal community was increasingly dominated over spring by the potentially toxin-producing genus Pseudonitzschia that was acclimated to high and variable light conditions characteristic of a thinner ice habitat with mobile snow cover. In comparison, the multi-year ice harbored more shade-acclimated algae of mixed composition. This work highlights the potential for heterotrophy in sea ice habitats of the High Arctic, including first measurements of such O2-uptake in multi-year ice floes. Observed differences in photophysiology between algae of these sea ice types suggests that a shift toward higher light availability and a younger sea ice cover with climate change does not necessarily result in a more productive system. Instead, it may favor future sea ice algal communities of different species composition, with lower photosynthetic potential but greater resilience to stronger and more variable light conditions.

Carbon flows through the microbial food web of first-year ice in resolute passage (Canadian High Arctic)

1997 ◽  
Vol 11 (1-2) ◽  
pp. 173-189 ◽  
Author(s):  
Alain F. Vézina ◽  
Serge Demers ◽  
Isabelle Laurion ◽  
Télesphore Sime-Ngando ◽  
S. Kim Juniper ◽  
...  
Keyword(s):  
Food Web ◽  
High Arctic ◽  
Microbial Food Web ◽  
First Year ◽  
Canadian High Arctic

scholarly journals The Borehole Jack—Is It a Useful Arctic Tool?

1987 ◽  
Vol 109 (4) ◽  
pp. 391-397 ◽  
Author(s):  
Nirmal K. Sinha
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Melting Point ◽  
Sea Ice ◽  
High Arctic ◽  
Test System ◽  
Simultaneous Recording ◽  
First Year ◽  
Test Procedures ◽  
Operational Conditions

As the working temperatures in ice are very close to its melting point, it behaves viscoelastically and experiences what is commonly known as high temperature embrittlement. Its mechanical properties are rate sensitive and analysis must include load and displacement history. Borehole jack tests can be improved by the use of an electrohydraulic pump in conjunction with simultaneous recording of pressure and diametral displacement as a function of time. These small but significant modifications in the test procedures permit analysis of the response of a borehole jack test system under operational conditions in the High Arctic in first-year and multi-year sea ice.

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