Sample collection: The sampling was part of the Canadian Arctic Shelf Exchange Study (CASES) in which CCGS Amundsen was frozen in Franklin Bay in the coastal Beaufort Sea (Station FB/200) during winter. Upper mixed-layer microbial plankton communities were sampled 5m below the water surface using the ship CTD rosette system equipped with 12L Niskins during openwater conditions. During the time that the ship was frozen in Franklin Bay from December 2003 to early June 2004, samples were taken using a 5L Niskin bottle from 3m below the bottom ice through a 300mm hole that had been drilled 500m upstream of the ship. HPLC pigment analysis: One to two liter samples of water were filtered onto Whatman GF/F filters and stored frozen at -80C until analysis. Phytoplankton pigments on the GF/Fs were extracted in 3mL of 95 percent MeOH and 100 uL of the extracts was injected into a Varian ProStar HPLC equipped with a Symmetry C8 column. The HPLC peaks were detected by diode-array spectroscopy (350-750nm) and absorbance chromatograms were obtained at 440 (for chls) and 450nm (for carotenoids). Chlorophylls were also detected by fluorescence (excitation: 440nm; emission: 650nm). The HPLC solvent protocol was based on gradient dilution with two solvent mixtures (Zapata et al. 2000): a methanol, acetonitrile, and aqueous pyridine (50:25:25 v:v:v) solution; and a methanol, acetonitrile, and acetone (20:60:20 v:v:v) solution. The flow rate was 1mL/ min, and the equilibration time was 7min.

This dataset consists of vertical profiles of discrete depth sampled weekly at a fixed station under the ice in Franklin Bay (Southeastern Beaufort Sea) for chlorophyll a concentration of different size fractions: >0.7µm and >5µm. Sampling took place from December 2003 to May 2004 through the moon-pool of the CCGS Amundsen for depth ranging from 10m to the bottom and through a hole in the ice cover for the surface depth (3-10m). Chlorophyll a concentrations were determined by fluorimetry.

This study presents sea surface concentrations of marine dimethylsulfide (DMS) measured across the Labrador Sea and the Canadian Arctic Archipelago during summer of 2017 (July-August). Using a novel automated instrument (ACT-MIMS) more than 2500 DMS observations were collected at high frequency alongside ancillary measurements of salinity, temperature, fluorescence (chlorophyll a proxy), solar radiation, ice concentration and the algal precursor of DMS, dimethylsulfoniopropionate. DMS concentrations ranged from ca. 1 to 32 nmol L-1 (average of 6 nmol L-1) in 2017 over an area covering a wide range of contrasting marine environments from coastal to open ocean, ice-free waters, as well as under-ice waters. Surface water DMS hotspots were measured in association with thermohaline oceanographic features in high productivity coastal waters, as well as with the presence of ponded first-year ice (FYI). Nighttime increases and daytime decreases of DMS concentrations were also observed in productive areas of the Labrador Sea and Davis Strait continental shelf. The association of DMS concentrations with diurnal solar radiation variation suggests the involvement of photobiological processes. Overall, our results strengthen the view that aqueous DMS cycling in the Arctic is intimately linked with sea ice dynamics and physiological responses to light. As such, future changes in the seasonality of the Arctic cryosphere will likely play an important role in shaping DMS emissions, although the sign and magnitude of the change remain highly uncertain.

Field observations were made in the southern Beaufort Sea and the Amundsen Gulf as part of CASES 2003 expedition. Samples were collected during the first two legs of the expedition from 13 September to 14 October 2003 (open water) and from 15 October to 25 November 2003 (newly formed sea ice) onboard the Canadian icebreaker CCGS Amundsen. Temperature and salinity profiles were obtained using a SeaBird 911 Conductivity¿Temperature¿Depth (CTD) probe. Nutrient concentrations (nitrate plus nitrite, phosphate, and silicate) were determined on fresh samples (within 1 h of sampling) using standard colorimetric methodologies adapted for use on an Auto-Analyzer 3 (Bran þ Luebbe). A RAMSES ASC scalar hyperspectral irradiance sensor (TriOS) was mounted on the flight bridge to measure downwelling irradiance with 1 nm intervals during the day. A total of 50 and 102 discrete water samples were collected over the euphotic zone at 13 and 20 stations for legs 1 and 2, respectively for fluorometrically chlorophyll a measurements and absorption analysis of phytoplankton, non-algal particules (NAP) and colored dissolved organic matter (CDOM). Water samples (preserved in acidic Lugol solution) were enumerated and identified to the lowest possible taxonomic rank using an inverted microscope. Concentrations of chlorophyll a and chlorophyll b were obtained by HPLC measurements and these two pigments were used for the calculation of the ratios of chl b to chl a.

ArcticNet and IMG-Golder established southern and eastern Beaufort Sea Marine Observatories in 2011. The first pair of moorings (BRA and BRB) is in the southern Beaufort Sea, roughly 100 nautical miles northwest of Tuktoyaktuk. These deployments aimed at maintaining the existing ArcticNet time series initiated in 2009 in collaboration with Imperial Oil and BP. The second observatory, also deployed in 2011, consisted of two moorings (BR1 and BR2) north of the Mackenzie Trough at the western limit of the Beaufort Sea. Another pair of moorings BRG and BRK, launched in 2012 and 2014, are located off the northwest coast of Banks Island, starting a time series in the northeastern Beaufort Sea where year-round measurements have never been obtained before. Finally, two new moorings (BR3 and BR4) were also deployed at the end of the program in 2014 near BR2 and BRG respectively. For every year of deployment, each mooring line was equipped with various oceanographic instruments attached at different depths from approximately 150 m to 750 m. Moored instruments included conductivity-temperature sensors, ice profiling sonars, particle analyzers, current meters, current profilers, and sediment traps. Datasets include currents, ice draft and velocities, water levels, temperature, salinity and turbidity, chlorophyll, suspended particulate size and concentration, and vertical carbon flux; See CCIN10476 for Vertical flux data on Phyto and Zooplankton as well as on chemical parameters such as POC. Data are quality assessed/quality controlled (QA/QC) following the Climate and Forecast (CF http://cfconventions.org/) conventions and building upon the open-source Integrated Marine Observatory System (IMOS) toolbox developed for Matlab© by the Australian Ocean Data Network (AODN). The five moorings provided ready to use quality data for the period 2011-2015. BRG and BR1 time series were extended along with two moorings BR3 and BRK until 2018 during the iBO project (CCIN 13107).

Free-drifting, short-term particle interceptor traps were deployed from the CCGS Amundsen on eight occasions between 23 September and 16 October 2005. The traps were deployed at two or three depths below the euphotic zone (from 25 to 150 m) for 8 to 20 h. The sinking material was analyzed for particulate inorganic carbon, particulate and dissolved organic carbon, biogenic and lithogenic silica and chlorophyll a concentrations. Phytoplankton abundance and composition, fecal pellet abundance and biovolume and bacterial abundances were also assessed for the sinking material. Water column samples, from depths between 10 and 150 m, were collected to quantify fecal pellets. Lastly, phytoplankton from the deep chlorophyll maximum depth was collected and their sinking velocity determined using settling columns.

Sinking export of organic material was investigated during the fall of 2006, using free-drifting, short-term particle interceptor traps . The particle interceptor traps were deployed at 9 stations along a transect spanning between the North Water polynya (Baffin Bay) and the Beaufort Sea. The traps were deployed from the CCGS Amundsen at three depths below the euphotic zone (50, 100 and 150 m) for a period between 8 and 29 hours. The analyses on the sinking material included total chlorophyll a and phaopigments (fluorometric determination), particulate organic carbon and nitrogen, biogenic silica, cell composition and abundance and fecal pellet abundance.

The iBO project has supported the deployment of four moorings at key locations identified during the previous northern and southern Beaufort Sea monitoring initiatives (see CCIN 11925 ArcticNet-Industry 2009-2011 moorings and CCIN 11975 BREA 2011-2015 moorings). Since fall 2015, BRG and BR1 from BREA were redeployed along with two new moorings BRK and BR3. For every year of deployment, each mooring line was equipped with various oceanographic instruments attached at different depths from approximately 150 m to 750 m. Moored instruments include conductivity-temperature sensors, ice profiling sonars, particle analyzers, current meters, current profilers, and sediment traps. Datasets include currents, ice draft and velocities, water levels, temperature, salinity and turbidity, chlorophyll, suspended particulate size and concentration, and vertical carbon flux. Data collected were quality assessed/quality controlled (QA/QC) following the Climate and Forecast (CF http://cfconventions.org/) conventions, and building upon the open-source Integrated Marine Observatory System (IMOS) toolbox developed for Matlab© by the Australian Ocean Data Network (AODN). The four moorings provided ready to use quality data for the period 2015-2017. BR1 provided an extra year of data for 2017-2018, whereas BR3, BRG, and BRK are still at sea and being recovered (Fall 2019). The program ended officially in 2018; however, Amundsen Science and its collaborators maintain the observatory and monitoring capacity in the region with one mooring BRG pending new funding and interests for the program.

The datasets present new data from microscopic counts and selected nutrient and physical data assembled from the following missions. Aboard the CCGS Louis St-Laurent: IPY Canada's Three Oceans 2007. Aboard the CCGS Amundsen: International Polar Year (IPY) Circumpolar Flaw Lead Study 2008; ArcticNet 2008. Temporal coverage is July-September. Cell density of the three sub-clades MAST-1A, MAST-1B and MAST-1C was measured by cell-counts using fluorescent in situ hybridization with taxa-specific probe. Biomass of phototrophic organisms, of different size classes, was obtained by counts of DAPI-stained cells under epifluorescence microscopy. Samples for total chlorophyll a (chl a) were filtered onto GF/F filters, extracted in either ethanol or acetone and analysed by spectrofluorometry. Chl a was also measured for the < 3 µm size fraction, and chl a in the < 3 µm size fraction was calculate by simple substraction. CCGS Amundsen data: Temperature, salinity, transmissivity, oxygen, and photosynthetically active radiation were provided by Dr. Y. Gratton (Institut National de la Recherche Scientifique, Québec). Nitrate and Phosphate concentrations were provided by Dr. J.-É. Tremblay (Université Laval, Québec). CCGS Louis St-Laurent data were supplied by Drs. E.C. Carmack and J. Nelson (Institute of Ocean Sciences, Sidney, B.C.). Distance to ice edge was obtained from the Canadian Ice Services (http://ice-glaces.ec.gc.ca).

The datasets present new data from microscopic counts and selected nutrient and physical data assembled from the following cruises. Aboard the CCGS Amundsen: ArcticNet Expeditions 2006, 2008, 2009, 2010; International Polar Year (IPY) Circumpolar Flaw Lead Study 2008 and MALINA Project 2009 (French IPY project headed by Dr. M. Babin). Aboard the CCGS Louis St-Laurent: IPY Canada's Three Oceans 2007. Temporal coverage is Feb.-Nov., but varies by year, with the greatest sampling effort in July-Oct. Cryothecomonas abundance was measured by cell-counts using fluorescent in situ hybridization with a taxon-specific probe. Biomass of phototrophic and heterotrophic organisms, of different size classes, was obtained by counts of DAPI-stained cells under epifluorescence microscopy. Samples for total chlorophyll a (chl a) were filtered onto GF/F filters, extracted in either ethanol or acetone and analysed by spectrofluorometry. Chl a was also measured for the < 3 µm size fraction. CCGS Amundsen data: Temperature, salinity, oxygen, and photosynthetically active radiation were provided by Dr. Y. Gratton (Institut National de la Recherche Scientifique, Québec). Nitrate and Phosphate concentrations were provided by Dr. J.-É. Tremblay (Université Laval, Québec). CCGS Louis St-Laurent data were supplied by Drs. EC Carmack and John Nelson (Institute of Ocean Sciences, Sidney, B.C.). Distance to ice edge was obtained from the Canadian Ice Services (http://ice-glaces.ec.gc.ca).