Overview of the MOSAiC expedition: Physical oceanography

Arctic Ocean properties and processes are highly relevant to the regional and global coupled climate system, yet still scarcely observed, especially in winter. Team OCEAN conducted a full year of physical oceanography observations as part of the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC), a drift with the Arctic sea ice from October 2019 to September 2020. An international team designed and implemented the program to characterize the Arctic Ocean system in unprecedented detail, from the seafloor to the air-sea ice-ocean interface, from sub-mesoscales to pan-Arctic. The oceanographic measurements were coordinated with the other teams to explore the ocean physics and linkages to the climate and ecosystem. This paper introduces the major components of the physical oceanography program and complements the other team overviews of the MOSAiC observational program. Team OCEAN’s sampling strategy was designed around hydrographic ship-, ice- and autonomous platform-based measurements to improve the understanding of regional circulation and mixing processes. Measurements were carried out both routinely, with a regular schedule, and in response to storms or opening leads. Here we present alongdrift time series of hydrographic properties, allowing insights into the seasonal and regional evolution of the water column from winter in the Laptev Sea to early summer in Fram Strait: freshening of the surface, deepening of the mixed layer, increase in temperature and salinity of the Atlantic Water. We also highlight the presence of Canada Basin deep water intrusions and a surface meltwater layer in leads. MOSAiC most likely was the most comprehensive program ever conducted over the ice-covered Arctic Ocean. While data analysis and interpretation are ongoing, the acquired datasets will support a wide range of physical oceanography and multi-disciplinary research. They will provide a significant foundation for assessing and advancing modeling capabilities in the Arctic Ocean

Secretory IgA Induces Tolerogenic Dendritic Cells through SIGNR1 Dampening Autoimmunity in Mice.

IgA plays ambivalent roles in the immune system. The balance between inhibitory and activating responses relies on the multimerization status of IgA and interaction with their cognate receptors. In mucosal sites, secretory IgA (SIgA) protects the host through immune-exclusion mechanisms, but its function in the bloodstream remains unknown. Using bone marrow-derived dendritic cells, we found that both human and mouse SIgA induce tolerogenic dendritic cells (DCs) following binding to specific ICAM-3 grabbing nonintegrin receptor 1. This interaction was dependent on Ca(2+) and mannose residues. SIgA-primed DCs (SIgA-DCs) are resistant to TLR-dependent maturation. Although SIgA-DCs fail to induce efficient proliferation and Th1 differentiation of naive responder T cells, they generate the expansion of regulatory T cells through IL-10 production. SIgA-DCs are highly potent in inhibiting autoimmune responses in mouse models of type 1 diabetes and multiple sclerosis. This discovery may offer new insights about mucosal-derived DC immunoregulation through SIgA opening new therapeutic approaches to autoimmune diseases

Microstructure profiler raw data (MSS 90L sno 046) during legs 1-3 of the MOSAiC expedition in 2019/2020

During the MOSAiC drift, vertical profiles of turbulence and auxiliary parameters were measured with MSS microstructure profilers manufactured by Sea and Sun Technology, Germany. Here, the raw binary data from one of in total three different probes deployed during the drift is archived, in the instrument-specific .MRD data format. Every profile is stored in one individual binary file

Microstructure profiler raw data (MSS091) during legs 4 and 5 of the MOSAiC expedition in 2020

During the MOSAiC drift, vertical profiles of turbulence and auxiliary parameters were measured with MSS microstructure profilers manufactured by Sea and Sun Technology, Germany. Here, the raw binary data from one of in total three different probes deployed during the drift is archived, in the instrument-specific .MRD data format. Every profile is stored in one individual binary file

Turbulent microstructure profile (MSS) measurements from the MOSAiC drift, Arctic Ocean

During the year-long drift expedition MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) from September 2019 to September 2020, we obtained an unprecedented data set of vertical turbulent dissipation rate profiles and high resolved hydrodynamic properties, including oxygen concentration and fluorescence, also covering the winter season. Nearly 1,700 individual profiles, covering the upper ocean down to approximately 400~m, were collected on a near-daily base and complemented with several periods of intensified continuous sampling

Turbulent microstructure profile (MSS) measurements from the MOSAiC drift, Arctic Ocean, version 2

During the year-long drift expedition MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) from September 2019 to September 2020, we obtained an unprecedented data set of vertical turbulent dissipation rate profiles and high resolved hydrodynamic properties, including oxygen concentration and fluorescence, also covering the winter season. Nearly 1,700 individual profiles, covering the upper ocean down to approximately 400~m, were collected on a near-daily base and complemented with several periods of intensified continuous sampling. Version 2: To ensure the quality of the dataset, we compared the MSS data to the Polarstern and Ocean City CTD data, which provide the only in-situ calibrated measurements of salinity. As casts of two different instruments were rarely co-located, this comparison was done statistically, i.e., by comparing as many as possible pairs of casts closest in time. Most data channels are found to agree well, with the exception of the casts performed with the profiler MSS055, which was mostly used during leg 3 and was equipped with a substitute conductivity sensor. For this probe, a calibration cast was performed with the MSS attached to the Ocean City CTD on February 2, 2020, which showed a constant offset in conductivity of 0.11 mS/cm. After reprocessing the affected data with this offset correction, values were in good agreement with the CTD data. In addition, we calibrated the dissolved oxygen readings from MSS091 (used during legs 4 and 5) with the CTD data

Microstructure profiler raw data (MSS_55_IOW) during leg 3 of the MOSAiC expedition in 2020

During the MOSAiC drift, vertical profiles of turbulence and auxiliary parameters were measured with MSS microstructure profilers manufactured by Sea and Sun Technology, Germany. Here, the raw binary data from one of in total three different probes deployed during the drift is archived, in the instrument-specific .MRD data format. Every profile is stored in one individual binary file

Under-ice temperature and salinity measurements at Ice Ridge Observatory during MOSAiC from an RBR Concerto CTD

Two RBR Concerto Conductivity Temperature Depth (CTD) sensors (SN 60611 & SN 60610) were deployed as part of the Sea Ice Ridge Observatory, also called Fort Ridge, in the Arctic Ocean during the 2nd leg of the MOSAiC ice drift expedition in February 2020. The CTDs are autonomous instruments that measured conductivity (salinity), temperature, and pressure (depth) approximately 2-3 m below the sea ice on either side of a large ice ridge. The RBR 60610 was lost due to ice rafting before data was downloaded. The RBR 60611 was recovered in May 2020, resulting in one time series between January 3rd and May 6th2020. RBR 60611 was redeployed on May 6th but also lost due to ice rafting shortly after. Each CTD was deployed together with a Nortek Signature1000 acoustic Doppler current profiler (doi:10.1594/PANGAEA.941882), installed at a 2 m distance. Here we describe the instrument hardware, setup, and processing that resulted in the final data set. The instruments were deployed as part of the project Ridges - Safe HAVens for ice-associated Flora and Fauna in a Seasonally ice-covered Arctic OCean (HAVOC), funded by the Research Council of Norway, project number: 280292

Under-ice current and turbulence raw data (Nortek Signature1000 Acoustic Doppler profilers nortek_100098) at Ice Ridge Observatory during MOSAiC expedition

Two Nortek Signature1000 acoustic Doppler current profilers (SN 100098 & SN 101048) were deployed as part of the Sea Ice Ridge Observatory (also called Fort Ridge) in the Arctic Ocean during the 2nd leg of the MOSAiC ice drift expedition in February 2020. The ADCPs are autonomous instruments that measured ice-relative horizontal and vertical ocean currents and turbulence in the upper ~20 m of the water column. The instruments were deployed under the ice, pointing downward on either side of a large ice ridge. In addition to currents, temperature, pressure, tilt, and compass direction were measured. Both instruments were eventually lost due to ice rafting, resulting in one time series between January 3rd and May 6th2020 and one between January 3rd and February 21st, 2020. This dataset contains the rawdata for adcp_100098. Nortek Signature software (Nortek Discover) is needed to read and convert the data (https://www.nortekgroup.com/software). For more information see the Nortek Signature Principles of Operation (https://www.nortekgroup.com/assets/software/N3015-011-SignaturePrinciples.pdf). A processed and temporally averaged version of this dataset together with a data report can be found under doi:10.1594/PANGAEA.941882