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.

The navigation data of the Amundsen scientific expeditions between 2003 and 2019 were recorded with the Position and Orientation Systems for Marine Vessels (POS-MV) and C-Nav Differential Global Navigation Satellite System (DGNSS) Precise Point Positioning systems. Two sets of controlled data are provided for each year of expedition. The first set is at time intervals of seconds for every day of the cruise and the second set is at 15 minute intervals. The data consist of Latitude, Longitude, Heading, Roll, Pitch, Heave, Track, Speed and Global Positioning System (GPS) sources at the second time intervals. The vessel's tracks in .kml (Google Earth format) were derived from the 15 minute time intervals dataset and are also provided. Research programs participating in the Amundsen expeditions between 2003 and 2017 were CASES, ArcticNet, IPY-CFL, Solas, Geotraces, Malina, IOL and BP, Jamstec, Netcare, Weston, BREA, iBO and GreenEdge.

The data set is composed of raw files recorded with the Kongsberg Maritime SX90 long-range, low frequency (20-30 kHz) fisheries sonar during the CCGS Amundsen 2013 summer expedition in the Eastern Canadian Arctic. The sonar transducer is lowered 2.5 feet below the hull through a gate-valve. The cylindrical 256-elements transducer allows both a horizontal and a vertical sound transmission, and the omni-directional (horizontal) sonar beam can be tilted from +10 to -60 degrees to scan a large portion of the water column. The raw acoustic data were saved onto an external drive and print screens of interesting targets (fish schools) were recorded.

Real-time atmospheric measurements were made on board the CCGS Amundsen. Sampling lines were placed on the forward mast of the ship, and instruments were housed in a sampling shed located on the top deck. Mixing ratios of volatile organic compounds (VOCs: dimethylsulfide, acetone, methanol, benzene, etc.) were measured using proton-transfer-reaction mass spectrometry. Aerosol size distributions between 10 and 500 nm were measured using a scanning mobility particle sizer and total aerosol number concentrations > 3 nm were measured using an ultrafine condensation particle counter. All data have time resolution of minutes.

During the ArcticNet annual cruises of the research icebreaker CCGS Amundsen, characteristics of the near-surface atmosphere (basic meteorological elements, incident radiation) are monitored. Central to this integrated dataset, the following meteorological variables were recorded at 1 minute intervals (instrument used to collect each variable is in parentheses, and approximate instrument height above surface is indicated): wind speed (RM Young Wind Monitor 05106-10) - 16m height; wind direction (RM Young Wind Monitor 05106-10) -16m height; air temperature (Vaisala HMP45C) - 15m height; relative humidity (Vaisala HMP45C) -15m height; and, surface temperature (Apogee IR Transducer SI-111) - 8m height, atmospheric pressure. All instruments were mounted on a meteorological tower on the bow of the research icebreaker CCGS Amundsen, except for the IR transducer SI-111, which was mounted on top of the gunwale at the ship's bow, overlooking the water surface.

Processed atmospheric ceiling heights were recorded from a CT25K ceilometer. The instrument was mounted on the CCGS Amundsen icebreaker on the port side directly behind the ship's wheelhouse. Data were collected during transit, set transects, 24-hour stations, and multi-day drift stations. The instrument was running continuously during the IPY-CFL project, with only minor interruptions for maintenance activities.

The surface temperature of the target within the passive microwave (PMW) systems field of view were collected on a high temporal resolution. An infrared transducer was positioned on the port side of the CCGS Amundsen, at a height of approximately 7 meters. Data collection occurred every 15 seconds. The instrument collected data throughout the entirety of the Amundsen Cruise at a fixed angle. Brightness temperature data of target is in degrees Celsius.

During the ArcticNet annual cruises of the research icebreaker CCGS Amundsen, characteristics of the near-surface atmosphere (basic meteorological elements, incident radiation) are monitored. Central to this integrated dataset, the following meteorological variables were recorded at 1 minute intervals (instrument used to collect each variable is in parentheses, and approximate instrument height above surface is indicated): wind speed (RM Young Wind Monitor 05106-10) - 16m height; wind direction (RM Young Wind Monitor 05106-10) -16m height; air temperature (Vaisala HMP45C) - 15m height; relative humidity (Vaisala HMP45C) -15m height; and, surface temperature (Apogee IR Transducer SI-111) - 8m height, atmospheric pressure. All instruments were mounted on a meteorological tower on the bow of the research icebreaker CCGS Amundsen, except for the IR transducer SI-111, which was mounted on top of the gunwale at the ship's bow, overlooking the water surface.

The dataset is composed of Ichthyoplankton and zooplankton captured during the ArcticNet cruise aboard the CCGS Amundsen from 2017 to 2019. Three samplers fitted with 200 µm to 500 µm mesh nets were used for zooplankton collection . One was a metallic structure with 4 nets of 1 square meter opening each (2x2 multiple net sampler) for water column integrated sampling pulled vertically over from 10 m above the bottom to the surface to catch mesozooplankton. The other sampler was 2 nets of 1 square meter opening each towed at 10 m depth for 20 minutes at 2 knots to catch ichthyoplankton and macrozooplankton. Finally, a 0.5 square meter opening multinet Hydrobios for stratified sampling into nine layer also hauled vertically from 10 m above the sea bottom to the surface. Zooplankton samples were preserved in a 10% buffered formalin seawater solution and were sieved through 1000 µm and 200 µm sieves for analysis. Ichthyoplankton was identified to the lowest taxonomic level possible, a sub-sample was measured and all larvea were kept in ethanol.

To obtain the data, water samples of vertical profiles were firstly collected from the Rosette onboard the CCGS Amundsen, and then analyzed with instruments both onboard and in the lab in University of Manitoba. The total mercury were measured on a Tekran 2600 Model with the method EPA 1631 in the Portable In-situ Laboratory for Mercury Species onboard, while the methylmercury data were analyzed with the method EPA 1630 in the Ultra-Clean Trace Element Laboratory, which is located at the University of Manitoba. The main data types are the contaminants (along with O18 isotopes and dissolved organic carbon) concentrations in vertical profiles at the study sites.