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.

Total inorganic carbon, alkalinity, total organic carbon, and salinity measured in melted ice core sections. Full core profiles with 10-cm resolution taken weekly at Takatuk. Partial pressure of CO2 measured 2-3 times per week through peepers at three depths at each of 6 locations, 3 at Takatuk and 3 at Bruney Island. Total inorganic carbon measured coulometrically, alkalinity by potentiometric titration, organic carbon by high temperature catalytic combustion, and salinity by diffraction. pCO2 measured by gas chromatograph.

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.

Sea ice drift data were obtained from an array of ten ice beacons and one ice mass balance buoy launched from the CCGS Amundsen in the marginal ice zone of the southern Beaufort Sea in September, 2009. From this array, four triangular configurations were selected, hereinafter referred to as triplets A to D, to monitor sea ice deformation with initial inter-beacon distances of approximately 11, 11, 11.5, and 7 km for the shortest leg, and 15, 37, 11.5, and 12.5 km for the longest leg, respectively. Triplets A to D were deployed on multiyear ice (MYI) and labeled according to their proximity to the continental coastline, with Triplet A located closest to the coastline and then sequentially further away through to Triplet D. Position coordinates were available for all beacons in: Triplet A until October 6th; Triplet B until November 4th; Triplet C until November 25th, and Triplet D until November 3rd, yielding time intervals with durations of 28, 56, 77, and 59 days, respectively.

The IR Transducer is installed at the 400 level of the CCGS Amundsen icebreaker on the port side of the ship. The data recording is done on a separate storage module and then transferred to the backup drive. It can record the data at a user-specified time interval. The data file is an ASCII DAT file which can be processed either by the given software or in any graph plotting program. The sensor recorded continuously, 24 hours per day.

The data set is composed of raw files recorded with a SIMRAD EK60 three-frequency split-beam echosounder that was operated continuously during the annual ArcticNet (2005-2013) sampling expeditions in the Canadian Arctic and Subarctic aboard the CCGS Amundsen. Three 7° transducers were hull-mounted, two in oil-filled arctic wells protected by a 2.5 cm thick acoustically transparent polycarbonate plate (38 and 120 kHz) and one in a Traveocean piston well in direct contact with water (200 kHz). The acoustic signal was recorded continuously on a PC using ER60 software version 2.0.0. Ping interval was set at 2 or 3 s and the pulse length was set at 1.024 ms.

The BO105 helicopter on board the CCGS Amundsen was used during the northern section of the ArcticNet 1b leg to collect the ice thickness and video data along flight paths across Kennedy Channel. The main collection of data was done on three days between August 21 and August 24. In addition a total of 5 beacons were deployed on thick ice floes during these flights to monitor the ice drift of the floes within Kennedy Channel. From the two data sets the ice flux through Kennedy Channel can be estimated as shown below. At the end of the survey, ice thickness data was collected with an EM sled from a floe in Barrow Strait (74.0N and -96.4W) on September 1, 2013.

The dataset is composed of raw files recorded with a SIMRAD EK60 three-frequency split-beam echosounder that was operated continuously during the annual ArcticNet (2005-2014) sampling expeditions in the Canadian Arctic aboard the CCGS Amundsen. Three 7° transducers were hull-mounted, two in oil-filled arctic wells protected by a 2.5 cm thick acoustically transparent polycarbonate plate (38 and 120 kHz) and one in a Traveocean piston well in direct contact with water (200 kHz). The acoustic signal was recorded continuously on a PC using ER60 software version 2.0.0. Ping interval was set at 2 or 3 s and the pulse length was set at 1.024 ms.

Replicate cores spanning the entire thickness of the floe were taken from a single sampling site on a multi-year sea ice floe in the southwestern Beaufort Sea in August 2011 as part of the ArcticNet 2011 cruise of the CCGS Amundsen. Quantification of total mercury (THg), methylmercury (MeHg), Chlorophyll a, dissolved organic carbon (DOC) and delta 18O was performed on separate cores, and temperature and salinity profiles were recorded. THg was analyzed via CVAFS on board the Amundsen in the Portable In-situ Lab for Mercury Speciation (PILMS), while MeHg was analyzed via GC-CVAFS in the Ultra-Clean Trace Elements Lab (UCTEL) at the University of Manitoba. Chlorophyll a concentrations were analyzed onboard the Amundsen via fluorimetry, and salinity was recorded using a Hach Sension probe. DOC was analyzed by Dr. Michel Gosselin's lab at the Université du Québec à Rimouski via a high-temperature combustion Shimadzu TOC-5000A autoanalyzer. Delta 18O analysis was performed by G.G. Hatch Isotope Laboratories, University of Ottawa, Canada. Samples and standards (calibrated against several samples of Vienna - SMOW) were flushed with a gas mixture of 2 % CO2 in helium off-line, equilibrated at 21°C for 5 d, then analyzed using the Gasbench + DeltaPlus XP isotope ratio mass spectrometer (ThermoFinnigan, Germany).

The data set is composed of raw files recorded with a SIMRAD EK60 three-frequency split-beam echosounder that was operated continuously during the annual ArcticNet (2005-2010) and the 15 months IPY-CFL (2007-2008) sampling expeditions aboard the CCGS Amundsen. Three 7° transducers were hull-mounted, two in oil-filled arctic wells protected by a 2.5 cm thick acoustically transparent polycarbonate plate (38 and 120 kHz) and one in a Traveocean piston well in direct contact with water (200 kHz). The acoustic signal was recorded continuously on a PC using ER60 software version 2.0.0. Ping interval was set at 2 or 3 s and the pulse length was set at 1.024 ms.