Landfast Sea Ice Conditions in the Canadian Arctic: 1983 – 2009

We used Canadian Ice Service (CIS) digital charts from 1983 to 2009 to create a climatology of landfast sea ice in the Canadian Arctic. The climatology characterized the spatial distribution and variability of landfast ice through an average annual cycle and identified the mean onset date, breakup date, and duration of landfast ice. Trends in date and duration of onset and breakup were calculated over the 26-year period on the basis of CIS regions and sub-regions. In several sub-regions— particularly in the Canadian Arctic Archipelago—we calculated significant trends towards later landfast ice onset or earlier breakup, or both. These later onset and earlier breakup dates translated into significant decreases in landfast ice duration for many areas of the Canadian Arctic. For communities located in the most affected areas, including Tuktoyaktuk, Kugluktuk, Cambridge Bay, Gjoa Haven, Arctic Bay, and Pond Inlet, this shorter landfast ice season is of significant social, cultural, and economic importance. Landfast sea-ice duration in the interior of the Northwest Passage has not undergone any statistically significant decrease over the time series.Nous nous sommes appuyés sur les cartes numériques du Service canadien des glaces (SCG) pour les années 1983 à 2009 afin de produire la climatologie de la glace de mer de l’Arctique canadien. La climatologie permet de caractériser la distribution spatiale et la variabilité de la glace de mer au moyen d’un cycle annuel moyen, et de déterminer la date moyenne du commencement, la date de la débâcle et la durée de la glace de mer. Les tendances en matière de dates et de durées relativement au commencement et à la débâcle ont été calculées sur la période de 26 ans en fonction des régions visées par le SCG et des sous-régions. Dans plusieurs sous-régions — plus particulièrement dans l’archipel Arctique canadien — nous avons calculé d’importantes tendances indiquant des dates de commencement plus tardives de la glace de mer ou des dates de débâcle plus hâtives, ou les deux. Ces dates plus hâtives et plus tardives se traduisent par la réduction considérable de la durée de la glace de mer en maints endroits de l’Arctique canadien. Pour les localités situées dans la plupart des régions touchées, dont Tuktoyaktuk, Kugluktuk, Cambridge Bay, Gjoa Haven, Arctic Bay et Pond Inlet, cette saison de glace de mer plus courte revêt une grande importance sur les plans social, culturel et économique. Du point de vue statistique, la durée de la glace de mer à l’intérieur du passage du Nord-Ouest n’a pas connu de réduction importante au cours de cette période

Segmented flow coil equilibrator coupled to a proton-transfer-reaction mass spectrometer for measurements of a broad range of volatile organic compounds in seawater

We present a technique that utilises a segmented flow coil equilibrator coupled to a proton-transferreaction mass spectrometer to measure a broad range of dissolved volatile organic compounds. Thanks to its relatively large surface area for gas exchange, small internal volume, and smooth headspace-water separation, the equilibrator is highly efficient for gas exchange and has a fast response time (under 1 min). The system allows for both continuous and discrete measurements of volatile organic compounds in seawater due to its low sample water flow (100 cm3 min-1) and the ease of changing sample intake. The equilibrator setup is both relatively inexpensive and compact. Hence, it can be easily reproduced and installed on a variety of oceanic platforms, particularly where space is limited. The internal area of the equilibrator is smooth and unreactive. Thus, the segmented flow coil equilibrator is expected to be less sensitive to biofouling and easier to clean than membrane-based equilibration systems. The equilibrator described here fully equilibrates for gases that are similarly soluble or more soluble than toluene and can easily be modified to fully equilibrate for even less soluble gases. The method has been successfully deployed in the Canadian Arctic. Some example data from underway surface water and Niskin bottle measurements in the sea ice zone are presented to illustrate the efficacy of this measurement system

FTIR autecological analysis of bottom-ice diatom taxa across a tidal strait in the Canadian Arctic

A recent study demonstrated that an Arctic tidal strait, where a shoaled and constricted waterway increases tidally driven sub-ice currents and turbulence, represents a “hotspot” for ice algal production due to a hypothesized enhanced ocean-ice nutrient supply. Based on these findings, we sampled the bottom-ice algal community across the same tidal strait between the Finlayson Islands within Dease Strait, Nunavut, Canada, in spring 2017. Our objective was to examine cellular responses of sea-ice diatoms to two expected nutrient supply gradients in their natural environment: (1) a horizontal gradient across the tidal strait and (2) a vertical gradient in the bottom-ice matrix. Two diatom taxa, Nitzschia frigida and Attheya spp. in bottomice sections (0–2, 2–5, and 5–10 cm) under thin snow cover (<5 cm), were selected for Fourier Transform Infrared (FTIR) spectrochemical analysis for lipid and protein content. Results from the FTIR technique strongly supported the existence of a horizontal nutrient gradient across the tidal strait of the Finlayson Islands, while estimates of particulate organic carbon and chlorophyll a concentrations were difficult to interpret. The larger N. frigida cells appeared to be more sensitive to the suspected horizontal nutrient gradient, significantly increasing in lipid content relative to protein beyond the tidal strait. In contrast, the epiphytic diatoms, Attheya spp., were more sensitive to the vertical gradient: above 2 cm in the bottom-ice matrix, the non-motile cells appeared to be trapped with a depleted nutrient inventory and evidence of a post-bloom state. Application of the FTIR technique to estimate biomolecular composition of algal cells provided new insights on the response of the bottom-ice algal community to the examined spatial gradients that could not be obtained from conventional bulk measurements alone. Future studies of sea ice and associated environments are thus encouraged to employ this technique

Imaging air volume fraction in sea ice using non-destructive X-ray tomography

Although the presence of a gas phase in sea ice creates the potential for gas exchange with the atmosphere, the distribution of gas bubbles and transport of gases within the sea ice are still poorly understood. Currently no straightforward technique exists to measure the vertical distribution of air volume fraction in sea ice. Here, we present a new fast and non-destructive X-ray computed tomography technique to quantify the air volume fraction and produce separate images of air volume inclusions in sea ice. The technique was performed on relatively thin (4&ndash;22cm) sea ice collected from an experimental ice tank. While most of the internal layers showed air volume fractions 5 mm). While micro bubbles were the most abundant type of gas bubbles, most of the air porosity observed resulted from the presence of large and macro bubbles. The ice texture (granular and columnar) as well as the permeability state of ice are important factors controlling the air volume fraction. The technique developed is suited for studies related to gas transport and bubble migration

Micrometeorological and Thermal Control of Frost Flower Growth and Decay on Young Sea Ice

Frost flowers are transient crystal structures that form on new and young sea ice surfaces. They have been implicated in a variety of biological, chemical, and physical processes and interactions with the atmosphere at the sea ice surface. We describe the atmospheric and radiative conditions and the physical and thermal properties of the sea ice and atmosphere that form, decay, and destroy frost flowers on young sea ice. Frost flower formation occurred during a high-pressure system that caused air temperatures to drop to −30˚C, with relative humidity of 70% (an undersaturated atmosphere), and very calm wind conditions. The sea ice surface temperature at the time of frost flower initiation was 10˚–13˚C warmer than the air temperature. Frost flowers grew on nodules raised above the mean surface height by 5 mm, which were 4˚–6˚C colder than the bare, brine-wetted, highly saline sea ice surface that provided the necessary moisture. The cold nodules created potential water vapour supersaturation zones above them with respect to air over the brine skim. Frost flowers formed and grew overnight in the absence of shortwave radiation, while the net longwave radiation was negative and dominated the net all-wave radiation balance at the surface. The observed crystal habits of the frost flowers were long needles, betraying their origin from the vapour phase at temperatures between −20˚C and −30˚C. After a night of growth, frost flowers decayed in association with increased solar radiation, a net surface radiation balance of 0 W m-2, increased air and surface temperatures, increased wind speed, and decreased relative humidity. We hypothesize that these conditions increased vertical mixing, which eroded near-surface water vapour saturation and initiated sublimation. The frost flowers finally were rapidly destroyed by snowfall.Les fleurs de glace sont des structures cristallines transitoires qui se forment sur des surfaces de glace de mer nouvelles et jeunes. Elles découlent de divers processus et interactions biologiques, chimiques et physiques avec l’atmosphère, à la surface de la glace de mer. Nous décrivons les conditions atmosphériques et radiatives de même que les propriétés physiques et thermiques de la glace de mer qui forment, détériorent et détruisent les fleurs de glace sur la jeune glace de mer. La formation de fleurs de glace s’est produite lorsqu’un système de haute pression a fait baisser les températures de l’air à −30 ˚C, avec une humidité relative de 70 % (atmosphère sous-saturée) et un régime des vents très calme. À l’amorçage des fleurs de glace, la température à la surface de la glace de mer était de 10˚ à 13 ˚C plus chaude que la température de l’air. Les fleurs de glace se sont formées sur des nodules élevés au-dessus de la hauteur moyenne de la surface dans une mesure de 5 mm, ce qui était entre 4˚ et 6 ˚C plus froid que la surface de glace de mer brute, saumurée et fortement saline qui a fourni l’humidité nécessaire. En ce qui a trait à l’air au-dessus de l’écume de saumure, les nodules de froid ont créé des zones potentielles de sursaturation de vapeur d’eau au-dessus. Des fleurs de glace se sont formées et ont grossi pendant la nuit, en l’absence de rayonnement de courtes longueurs d’onde, tandis que le rayonnement net de grandes longueurs d’onde était négatif et dominait l’équilibre du rayonnement net de toutes ondes à la surface. L’habitus cristallin observé dans les fleurs de glace prenait la forme de longues aiguilles, trahissant son origine de la phase vapeur à des températures variant de −20 ˚C à −30 ˚C. Après une nuit de croissance, les fleurs de glace se sont détériorées en présence du rayonnement solaire accru, du bilan radiatif de la surface de 0 W m-2, des températures accrues de l’air et de la surface, de la plus grande vitesse du vent et de l’humidité relative réduite. Nous formulons l’hypothèse que ces conditions ont eu pour effet d’augmenter le mélange vertical, ce qui a érodé la saturation de vapeur d’eau près de la surface et déclenché la sublimation. Par la suite, les fleurs de glace ont été rapidement détruites par la chute de neige

Polar oceans and sea ice in a changing climate

Polar oceans and sea ice cover 15% of the Earth’s ocean surface, and the environment is changing rapidly at both poles. Improving knowledge on the interactions between the atmospheric and oceanic realms in the polar regions, a Surface Ocean–Lower Atmosphere Study (SOLAS) project key focus, is essential to understanding the Earth system in the context of climate change. However, our ability to monitor the pace and magnitude of changes in the polar regions and evaluate their impacts for the rest of the globe is limited by both remoteness and sea-ice coverage. Sea ice not only supports biological activity and mediates gas and aerosol exchange but can also hinder some in-situ and remote sensing observations. While satellite remote sensing provides the baseline climate record for sea-ice properties and extent, these techniques cannot provide key variables within and below sea ice. Recent robotics, modeling, and in-situ measurement advances have opened new possibilities for understanding the ocean–sea ice–atmosphere system, but critical knowledge gaps remain. Seasonal and long-term observations are clearly lacking across all variables and phases. Observational and modeling efforts across the sea-ice, ocean, and atmospheric domains must be better linked to achieve a system-level understanding of polar ocean and sea-ice environments. As polar oceans are warming and sea ice is becoming thinner and more ephemeral than before, dramatic changes over a suite of physicochemical and biogeochemical processes are expected, if not already underway.These changes in sea-ice and ocean conditions will affect atmospheric processes by modifying the production of aerosols, aerosol precursors, reactive halogens and oxidants, and the exchange of greenhouse gases. Quantifying which processes will be enhanced or reduced by climate change calls for tailored monitoring programs for high-latitude ocean environments. Open questions in this coupled system will be best resolved by leveraging ongoing international and multidisciplinary programs, such as efforts led by SOLAS, to link research across the ocean–sea ice–atmosphere interface

Melt Procedure Affects the Photosynthetic Response of Sea Ice Algae

The accuracy of sea ice algal production estimates is influenced by the range of melting procedures used in studies to obtain a liquid sample for incubation, particularly in relation to the duration of melt and the approach to buffering for osmotic shock. In this research, ice algal photophysiology from 14C incubations was compared in field samples prepared by three melt procedures: (i) a rapid 4 h melt of the bottommost ( < 1 cm) ice algal layer scraped into a large volume of filtered seawater (salinity 27–30), (ii) melt of a bottom 5 cm section diluted into a moderate volume of filtered seawater over 24 h (salinity 20–24), and (iii) melt of a bottom 5 cm section without any filtered seawater dilution over about 48 h (salinity 10–12). Maximum photosynthetic rate, photosynthetic efficiency and production at zero irradiance were significantly affected by the melt treatment employed in experiments. All variables were greatest in the highly diluted scrape sample and lowest in the bulk-ice samples melted in the absence of filtered seawater. Laboratory experiments exposing cultures of the common sea ice diatom Nitzschia frigida to different salinities and light conditions suggested that the field-based responses can be attributed to the rapid ( < 4 h) adverse effects of exposing cells to low salinities during melt without dilution. The observed differences in primary production between melt treatments were estimated to account for over 60% of the variability in production estimates reported for the Arctic. Future studies are strongly encouraged to replicate salinity conditions representative of in situ values during the melting process to minimize hypoosmotic stress, thereby most accurately estimating primary production

Physical length scales of wind-blown snow redistribution and accumulation on relatively smooth Arctic first-year sea ice

Snow thickness measurements over relatively smooth Arctic first-year sea ice, obtained near Cambridge Bay, Nunavut, Canada (2014, 2016 and 2017) and near Elson Lagoon, Alaska, USA (2003 and 2006), are analyzed to quantify physical length-scales and their relevant scaling behaviors. We use the Multi-Fractal Temporally Weighted Detrended Fluctuation Analysis (MF-TWDFA) method to detect two major physical length-scales from both the study areas. Our results suggest that physical processes underlying the formation of snow dunes are consistent and that the wind is the main process shaping the redistribution and variability of snow thickness. One scale, around 10 m, appears to be related to the formation of the snow "dunes", while the other scale, between 30 m and 60 m, is likely associated with the various interactions of the snow dunes including merging, calving and lateral linking showing self-organized characteristics. We suggest that a simple cellular automata model can be used to generate the variability of snow thickness on smooth Arctic first-year sea ice

Melt Procedure Affects the Photosynthetic Response of Sea Ice Algae

The accuracy of sea ice algal production estimates is influenced by the range of melting procedures used in studies to obtain a liquid sample for incubation, particularly in relation to the duration of melt and the approach to buffering for osmotic shock. In this research, ice algal photophysiology from 14C incubations was compared in field samples prepared by three melt procedures: (i) a rapid ≤ 4 h melt of the bottommost ( &lt; 1 cm) ice algal layer scraped into a large volume of filtered seawater (salinity 27–30), (ii) melt of a bottom 5 cm section diluted into a moderate volume of filtered seawater over 24 h (salinity 20–24), and (iii) melt of a bottom 5 cm section without any filtered seawater dilution over about 48 h (salinity 10–12). Maximum photosynthetic rate, photosynthetic efficiency and production at zero irradiance were significantly affected by the melt treatment employed in experiments. All variables were greatest in the highly diluted scrape sample and lowest in the bulk-ice samples melted in the absence of filtered seawater. Laboratory experiments exposing cultures of the common sea ice diatom Nitzschia frigida to different salinities and light conditions suggested that the field-based responses can be attributed to the rapid ( &lt; 4 h) adverse effects of exposing cells to low salinities during melt without dilution. The observed differences in primary production between melt treatments were estimated to account for over 60% of the variability in production estimates reported for the Arctic. Future studies are strongly encouraged to replicate salinity conditions representative of in situ values during the melting process to minimize hypoosmotic stress, thereby most accurately estimating primary production