ALBERT

Description: We present sea ice temperature and salinity data from first-year ice (FYI) and second-year ice (SYI) relevant to the temporal development of sea ice permeability and brine drainage efficiency from the early growth phase in October 2019 to the onset of spring warming in May 2020. Our dataset was collected in the central Arctic Ocean during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition in 2019 to 2020. MOSAiC was an international transpolar drift expedition in which the German icebreaker RV Polarstern anchored into an ice floe to gain new insights into Arctic climate over a full annual cycle. In October 2019, RV Polarstern moored to an ice floe in the Siberian sector of the Arctic at 85 degrees north and 137 degrees east to begin the drift towards the North Pole and the Fram Strait via the Transpolar Drift Stream. The data presented here were collected during the first three legs of the expedition, so all the coring activities took place on the same floe. The end dates of legs 1, 2, and 3 were 13 December, 24 February, and 4 June, respectively. The dataset contributed to a baseline study entitled, Deciphering the properties of different Arctic ice types during the growth phase of the MOSAiC floes: Implications for future studies. The study highlights downward directed gas pathways in FYI and SYI by inferring sea ice permeability and potential brine release from several time series of temperature and salinity measurements. The physical properties presented in this paper lay the foundation for subsequent analyses on actual gas contents measured in the ice cores, as well as air-ice and ice-ocean gas fluxes. Sea ice cores were collected with a Kovacs Mark II 9 cm diameter corer. To measure ice temperatures, about 4.5 cm deep holes were drilled into the core (intervals varied by site and leg) . The temperatures were measured by a digital thermometer within minutes after the cores were retrieved. The ice cores were placed into pre-labelled plastic sleeves sealed at the bottom end. The ice cores were transported to RV Polarstern and stored in a -20 degrees Celsius freezer. Each of the cores was sub-sampled, melted at room temperature, and processed for salinity within one or two days. The practical salinity was estimated by measuring the electrical conductivity and temperature of the melted samples using a WTW Cond 3151 salinometer equipped with a Tetra-Con 325 four-electrode conductivity cell. The practical salinity represents the the salinity estimated from the electrical conductivity of the solution. The dataset also contains derived variables, including sea ice density, brine volume fraction, and the Rayleigh number.

Description: We present sea ice temperature and salinity data from first-year ice (FYI) and second-year ice (SYI) relevant to the temporal development of sea ice permeability and brine drainage efficiency from the early growth phase in October 2019 to the onset of spring warming in May 2020. Our dataset was collected in the central Arctic Ocean during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition in 2019 to 2020. MOSAiC was an international transpolar drift expedition in which the German icebreaker RV Polarstern anchored into an ice floe to gain new insights into Arctic climate over a full annual cycle. In October 2019, RV Polarstern moored to an ice floe in the Siberian sector of the Arctic at 85 degrees north and 137 degrees east to begin the drift towards the North Pole and the Fram Strait via the Transpolar Drift Stream. The data presented here were collected during the first three legs of the expedition, so all the coring activities took place on the same floe. The end dates of legs 1, 2, and 3 were 13 December, 24 February, and 4 June, respectively. The dataset contributed to a baseline study entitled, Deciphering the properties of different Arctic ice types during the growth phase of the MOSAiC floes: Implications for future studies. The study highlights downward directed gas pathways in FYI and SYI by inferring sea ice permeability and potential brine release from several time series of temperature and salinity measurements. The physical properties presented in this paper lay the foundation for subsequent analyses on actual gas contents measured in the ice cores, as well as air-ice and ice-ocean gas fluxes. Sea ice cores were collected with a Kovacs Mark II 9 cm diameter corer. To measure ice temperatures, about 4.5 cm deep holes were drilled into the core (intervals varied by site and leg) . The temperatures were measured by a digital thermometer within minutes after the cores were retrieved. The ice cores were placed into pre-labelled plastic sleeves sealed at the bottom end. The ice cores were transported to RV Polarstern and stored in a -20 degrees Celsius freezer. Each of the cores was sub-sampled, melted at room temperature, and processed for salinity within one or two days. The practical salinity was estimated by measuring the electrical conductivity and temperature of the melted samples using a WTW Cond 3151 salinometer equipped with a Tetra-Con 325 four-electrode conductivity cell. The practical salinity represents the the salinity estimated from the electrical conductivity of the solution. The dataset also contains derived variables, including sea ice density, brine volume fraction, and the Rayleigh number.

Description: This data set contains the hydrographic profile data collected with a CTD rosette in a shelter on the ice (Ocean City) during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC). The CTD is an SBE911plus with 12 bottles, 5 liters each, operated with a small winch and crane in the shelter on the ice. The data set contains calibrated and quality-controlled parameters (temperature, conductivity, oxygen and their derived variables) as well as only pre-cruise calibrated parameters where no post-cruise calibration or quality control was applied (all other). CDOM fluorescence data are the exception. Quality control was performed but data have to be handled with care, as the sensor seems to have broken down during leg 3 such that no post-cruise calibration could be applied. The data are provided as text file (all cruise legs in one file) as well as in netCDF format (one file per cruise leg). The accuracy for salinity and conductivity is 0.004 while the accuracy for temperature is 0.002. Additional information on the sensor used for the final data set, the water depth as well as the availability of profile or bottle data is given in a separate info-text-file. Contact: Sandra.Tippenhauer@awi.de Quality flags are given based on paragraph 6. "Quality flags" from https://www.seadatanet.org/content/download/596/file/SeaDataNet_QC_procedures_V2_%28May_2010%29.pdf. QC flag meanings: 0 = unknown, 1 = good_data, 2 = probably good_data, 3 = probably bad data, 4 = bad data set to nan. This work was carried out and data was produced as part of the international Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC) with the tag MOSAiC20192020. We thank all persons involved in the expedition of the Research Vessel Polarstern during MOSAiC in 2019-2020 (AWI_PS122_00) as listed in Nixdorf et al. (2021).

Description: Second-year sea-ice thickness, draft, salinity, temperature, and density were measured during near-weekly surveys at the main second-year ice coring site (MCS-SYI) during the MOSAiC expedition (legs 1 to 3) and new second-year ice coring site leg 4, since the earlier site was not accessible any longer. The ice cores were extracted either with a 9-cm (Mark II) or 7.25-cm (Mark III) internal diameter ice corers (Kovacs Enterprise, US). This data set includes data from 18 coring site visits and were performed from 28 October 2019 to 20 July 2020 at coring locations within 50 m to each other in the MOSAiC Central Observatory. During each coring event, ice temperature was measured in situ from a separate temperature core, using Testo 720 thermometers in drill holes with a length of half-core-diameter at 5-cm vertical resolution. Ice bulk practical salinity was measured from melted core sections at 5-cm resolution using a YSI 30 conductivity meter. Ice density was measured using the hydrostatic weighing method (Pustogvar and Kulyakhtin, 2016) from a density core in the freezer laboratory onboard Polarstern at the temperature of –15°C. Relative volumes of brine and gas were estimated from ice salinity, temperature and density using Cox and Weeks (1983) for cold ice and Leppäranta and Manninen (1988) for ice warmer than –2°C. The data contains the event label (1), time (2), and global coordinates (3,4) of each coring measurement and sample IDs (13, 15). Each salinity core has its manually measured ice thickness (5), ice draft (6), core length (7), and mean snow height (22). Each core section has the total length of its top (8) and bottom (9) measured in situ, as well estimated depth of section top (10), bottom (11), and middle (12). The depth estimates assume that the total length of all core sections is equal to the measured ice thickness. Each core section has the value of its practical salinity (14), isotopic values (16, 17, 18) (Meyer et al., 2000), as well as sea ice temperature (19) and ice density (20) interpolated to the depth of salinity measurements. The global coordinates of coring sites were measured directly. When it was not possible, coordinates of the nearby temperature buoy 2019T62 (legs 1-3) or 2019T61 (leg 4) were used. Ice mass balance buoy 2019T62 installation is described in doi:10.1594/PANGAEA.940231, ice mass balance buoy 2020T61 installation is described in doi: 10.1594/PANGAEA.926580. Brine volume (21) fraction estimates are presented only for fraction values from 0 to 30%. Each core section also has comments (23) describing if the sample is from a new coring site or has any other special characteristics. Macronutrients from the salinity core will be published in a subsequent version of this data set.

Description: This data set contains the hydrographic water sample data collected with the ship based CTD rosette during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC). The CTD is an SBE911plus with 24 bottles, 12 liters each, operated with a winch and crane on the side of Polarstern. The data set contains calibrated and quality-controlled parameters (temperature, conductivity, oxygen and their derived variables) as well as only pre-cruise calibrated parameters where no post-cruise calibration or quality control was applied (all other). CDOM fluorescence data are the exception. Quality control was performed but data have to be handled with care, as the sensor seems to have broken down during leg 3 such that no post-cruise calibration could be applied. Due to issues during processing SPAR data is missing in the bottle data. The data are provided as text file (all cruise legs in one file) as well as in netCDF format (one file per cruise leg). The accuracy for salinity and conductivity is 0.004 while the accuracy for temperature is 0.002. Additional information on the sensor used for the final data set, the water depth as well as the availability of profile or bottle data is given in a separate info-text-file. Contact: Sandra.Tippenhauer@awi.de. Quality flags are given based on paragraph 6. "Quality flags" from https://www.seadatanet.org/content/download/596/file/SeaDataNet_QC_procedures_V2_%28May_2010%29.pdf. QC flag meanings: 0 = unknown, 1 = good_data, 2 = probably good_data, 3 = probably bad data, 4 = bad data set to nan. This work was carried out and data was produced as part of the international Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC) with the tag MOSAiC20192020. We thank all persons involved in the expedition of the Research Vessel Polarstern during MOSAiC in 2019-2020 (AWI_PS122_00) as listed in Nixdorf et al. (2021).

Description: Algal pigment concentrations were retrieved from samples from first-year (FYI) ice, during the whole MOSAiC expedition (Multidisciplinary drifting Observatory for the Study of Arctic Climate) in 2019 to 2020. During MOSAiC, RV Polarstern anchored into an ice floe to gain new insights into Arctic climate over a full annual cycle. Sea ice data were collected starting with the onset of the study, at 85 degrees north and 137 degrees east, following the drift towards the Fram Strait, and returning to the North Pole in the last leg of the expedition. Ice cores were collected at the various coring sites together with teams ICE and BGC (Nicolaus et al. 2022), to study the development of pigment patterns over time, on 3 specific ice-locations. Altogether, 292 samples have been collected and analysed. Ice cores were sliced in sections of 5-10 cm before analyses. Each of the sections was melted at room temperature after additions of filtered ambient seawater, under dark conditions. After extraction in 90 % acetone, samples were analysed using high-performance liquid chromatography (HPLC) on a Waters system (AWI). Algal pigments contain a multiple set of information. Firstly, pigment concentrations can show the presence of algal biomass in the various domains sampled. Secondly, marker pigments can reveal seasonal and temporal dynamics in algal community structure, by discerning specific algal classes like diatoms, cryptophytes, haptophytes and chlorophytes that have specific roles in biogeochemical cycles. Thirdly, certain pigments are indicative of the (photo)-physiological state of micro-algae and fourth, degradation products of the main chlorophyll a pigment further give an indication about senescence and grazing in the various habitats.

Description: Algal pigment concentrations were retrieved from ocean samples, during the whole MOSAiC expedition (Multidisciplinary drifting Observatory for the Study of Arctic Climate) in 2019 to 2020. During MOSAiC, RV Polarstern anchored into an ice floe to gain new insights into Arctic climate over a full annual cycle. Ocean data were collected starting with the onset of the study, at 85 degrees north and 137 degrees east, following the drift towards the Fram Strait, and returning to the North Pole in the last leg of the expedition. Ocean samples were collected with a CTD, either from the ship, or from the ice floe in Ocean City (Rabe et al. 2022). Altogether 216 samples have been collected and analysed. After extraction in 90 % acetone, samples were analysed using high-performance liquid chromatography (HPLC) on a Waters system. Algal pigments contain a multiple set of information. Firstly, pigment concentrations can show the presence of algal biomass in the various water masses sampled. Secondly, marker pigments can reveal seasonal and temporal dynamics in algal community structure, by discerning specific algal classes like diatoms, cryptophytes, haptophytes and chlorophytes that have specific roles in biogeochemical cycles. Thirdly, certain pigments are indicative of the (photo)-physiological state of micro-algae and fourth, degradation products of the main chlorophyll a pigment further give an indication about senescence and grazing in the various habitats.

Description: This data set contains the hydrographic profile data collected with the ship based CTD rosette during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC). The CTD is an SBE911plus with 24 bottles, 12 liters each, operated with a winch and crane on the side of Polarstern. The data set contains calibrated and quality-controlled parameters (temperature, conductivity, oxygen and their derived variables) as well as only pre-cruise calibrated parameters where no post-cruise calibration or quality control was applied (all other). CDOM fluorescence data are the exception. Quality control was performed but data have to be handled with care, as the sensor seems to have broken down during leg 3 such that no post-cruise calibration could be applied. The data are provided as text file (all cruise legs in one file) as well as in netCDF format (one file per cruise leg). The accuracy for salinity and conductivity is 0.004 while the accuracy for temperature is 0.002. Additional information on the sensor used for the final data set, the water depth as well as the availability of profile or bottle data is given in a separate info-text-file. Contact: Sandra.Tippenhauer@awi.de. Quality flags are given based on paragraph 6. "Quality flags" from https://www.seadatanet.org/content/download/596/file/SeaDataNet_QC_procedures_V2_%28May_2010%29.pdf. QC flag meanings: 0 = unknown, 1 = good_data, 2 = probably good_data, 3 = probably bad data, 4 = bad data set to nan. This work was carried out and data was produced as part of the international Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC) with the tag MOSAiC20192020. We thank all persons involved in the expedition of the Research Vessel Polarstern during MOSAiC in 2019-2020 (AWI_PS122_00) as listed in Nixdorf et al. (2021).

Description: Concentrations of Chlorophyll a and phaeopigments from CTD-rosette casts during the MOSAiC (PS122) drift expedition in the central Arctic Ocean. 2-4L of water were filtered onto precombusted GF/F filters (nominal pore size 0.7µm) and frozen at -80°C. Samples were subsequently extracted in 90°C acetone,homogenized using a cell mill, and meaured on the following day using a Turner flourometer, followed by an acidification step to determine pheopigments (see Knap et al. 1994 for details and calculations). Samples were collected roughly once per week from end of October 2019 to beginning of October 2020.

Description: This dataset gives an overview of the abundance of microorganisms (smaller than 20 µm) enumerated using flow cytometry (FCM) during the Multidisciplinary drifting observatory for the study of Arctic Climate (MOSAiC) sampled from ship-based and on-ice CTD rosettes during leg 1, 2, 3, 4 and 5 (November 2019 – September 2020). Additional expedition and sampling details can be found in the ECO-overview paper (Fong et al., to be submitted to Elementa). We thank all persons involved in the expedition of the Research Vessel Polarstern during MOSAiC in 2019-2020 (AWI_PS122_00) as listed in Nixdorf et al. (2021). Flow cytometry (FCM) is a fast, high-throughput method to enumerate the abundance of microorganism (smaller than 20 µm). FCM uses the hydrodynamic focusing of a laminar flow to separate and line up microscopic particles. When particles pass a laser beam, the generated light scattering can be used to estimate their cell size, obtain information about cell granularity and surface characteristics and determine fluorescence from inherent pigments or applied stains, such as DNA binding ones. Photosynthetic microorganisms have auto-fluorescent pigments, such as chlorophylls which in combination with the light scattering properties (cell size) or surface properties, can be used to group them into clusters of similar or identical organism types. Heterotrophic microorganisms, including archaea, bacteria and heterotrophic nanoflagellates, and virus do not have fluorescent pigments and require staining, for example using SYBR Green to stain Nucleic Acids (DNA/RNA) in order to distinguish these cells from other organic and inorganic particles in the sample. Samples for flow cytometric analysis were taken in triplicates or quadruplicates of 1.8 mL of sample water and fixed with 36 μL 25 % glutaraldehyde (0.5 % final concentration) at 4 °C in the dark for approximately 2 hours, then flash frozen in liquid nitrogen and stored at -80 °C until analysis. The abundance of pico- and nano-sized phytoplankton and heterotrophic nanoflagellates (HNF) were determined using an Attune® NxT, Acoustic Focusing Cytometer (Invitrogen by Thermo Fisher Scientific) with a 20 mW 488 nm (blue) laser. Autotrophic pico-and nano-sized plankton were counted directly after thawing and the various groups discriminated based on their red fluorescence (BL3) vs. orange fluorescence (BL2), red fluorescence (BL3) vs. side scatter (SSC) and orange fluorescence (BL2) vs. side scatter (SSC). For HNF analysis, the samples were stained with SYBR Green I for 2 h in the dark and 1-2 mL were subsequently measured at a flow rate of 500 µl min-1 following the protocol of Zubkov et al. 2007. The abundance of virus and bacteria was determined using a FACS Calibur (Becton Dickinson) flow cytometer with a 15 mW 480 nm (blue) laser. Prior analysis of virus and bacteria, samples were first thawed, diluted x10 and x100 with 0.2 μm filtered TE buffer (Tris 10 mM, EDTA 1 mM, pH 8), stained with a green fluorescent nucleic acid dye (SYBR Green I ; Molecular Probes, Eugene, Oregon, USA) and then incubated for 10 min at 80°C in a water bath (Marie et al. 1999). Stained samples were counted at a flow rate of around 60 µL min-1 and different groups discriminated on a biparametric plot of green florescence (BL1) vs. side scatter (SSC). This allowed to distinguish virus particles of different sizes, and different bacterial groups including low nuclear acid (LNA) and high nuclear acid (HNA) bacteria. Names of size groups of photosynthetic and heterotrophic organisms are in accordance to "Standards and Best Practices For Reporting Flow Cytometry Observations: a technical manual (Version 1.1)" (Neeley et al., 2023). A short summary is listed here: RedPico = picophytoplankton (1-2 µm); RedNano = Nanophytoplankton (2-20µm), which includes subgroups RedNano_small (2-5 µm), RedNano_large (5-20 µm); OraPico = Nanophytoplankton with more orange fluorescence; OraNano = Cryptophytes; OraPicoProk = Synechococcus; HetNano = heterotrophic nanoflagellates; HetProk = bacteria (and when present archaea); HetLNA = low nucleic acid (LNA) containing bacteria; HetHNA = high nucleic acid (HNA) containing bacteria with the subgroups HetProk_medium = HNA-bacteria subgroup with less fluorescence signal, HetProk_large = HNA-bacteria subgroup with more fluorescence signal and HetProk_verylarge = HNA-bacteria subgroup with very strong fluorescence signal; Virus = virus-like particles, including size refined subgroups: LFV (low fluorescence virus or small virus); MFV (medium fluorescence virus or medium virus); HFV (high fluorescence virus or large virus) according to Larsen et al., 2008. Exemplary plots showing the gating strategies that were followed can be found in "Interoperable vocabulary for marine microbial flow cytometry" (Thyssen et al., 2022).