MOSAiC expedition: Multidisciplinary drifting observatory for Arctic climate (2019–2020)

  1. MOSAiC project formally launches under AWI leadership

    Labels: MOSAiC project, Alfred Wegener

    The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) was organized as a year-long Arctic drift mission led by the Alfred Wegener Institute (AWI). Its central idea was to freeze a modern research icebreaker into sea ice and observe the coupled atmosphere–ice–ocean system across all seasons, including the polar night. Planning emphasized coordinated support ships, aircraft, and a large international science team.

  2. Polarstern departs Tromsø to begin expedition

    Labels: RV Polarstern, Troms

    Germany’s research icebreaker RV Polarstern sailed from Tromsø, Norway, marking the operational start of the MOSAiC field campaign. The ship headed toward the Siberian side of the Arctic Ocean with supporting logistics, aiming to enter the pack ice while it was still navigable in early autumn. This departure began the sequence of legs and resupply operations needed to keep year-round research going.

  3. Polarstern locks into chosen sea-ice floe

    Labels: Polarstern, Central Observatory

    After searching for a stable ice floe using helicopters and satellite information, the team selected a floe in the central Arctic and allowed Polarstern to become trapped in the ice. This moment created the expedition’s “Central Observatory,” a fixed reference point on drifting sea ice for coordinated measurements. It was a key transition from transit to long-term, on-ice operations.

  4. Distributed Network installed around Central Observatory

    Labels: Distributed Network, sea ice

    Teams deployed a “Distributed Network” of instruments extending tens of kilometers from the ship to measure how conditions vary across space, not just at one point. This network complemented intensive ship-and-camp observations by adding broader coverage of sea ice, ocean, and atmosphere conditions. Together, these systems helped connect local process studies to larger-scale Arctic behavior.

  5. First major winter resupply enables Leg II transition

    Labels: Kapitan Dranitsyn, winter resupply

    A scheduled resupply and personnel exchange in the polar night helped sustain the expedition through winter. The Russian icebreaker Kapitan Dranitsyn transferred people and supplies so research could continue without stopping. This demonstrated the expedition’s logistics concept: periodic rotations while the main observatory stayed embedded in drifting sea ice.

  6. Polarstern reaches record-high latitude during Arctic winter

    Labels: Polarstern, record latitude

    During the drift, Polarstern reached about 88°36′ N—roughly 156 km from the North Pole—setting a record for a ship operating that far north in winter conditions. The achievement mattered not as a “race,” but because it showed that year-round science from within central Arctic sea ice was feasible. It also kept continuous observations going through the darkest and coldest part of the year.

  7. Polarstern temporarily leaves ice to execute crew exchange

    Labels: Polarstern, buoys

    To complete pandemic-era logistics, Polarstern departed the Central Observatory in mid-May, leaving instruments behind to continue tracking the drift. This break created a gap in ship-based GPS records that was bridged using buoy data stationed on the ice. The event showed how MOSAiC relied on both human operations and autonomous systems to preserve continuity.

  8. COVID-19 forces revised crew-exchange and quarantine plan

    Labels: COVID-19, quarantine

    As the COVID-19 pandemic spread, MOSAiC’s planned logistics had to be redesigned to reduce infection risk. Incoming personnel were quarantined and tested, and the crew change could not be performed directly at the ice camp as first intended. These changes kept the mission running but added time pressure and operational complexity during the spring transition.

  9. Polarstern returns to observatory after exchange near Svalbard

    Labels: Polarstern, Svalbard

    After the off-floe crew change and resupply operations, Polarstern returned to the drifting observatory and resumed full operations in the central Arctic. This return helped preserve the expedition’s main scientific goal: capturing a continuous seasonal cycle of atmosphere, sea ice, and ocean processes. It also marked the transition into intensive summer melt-season observations.

  10. Original MOSAiC floe reaches Fram Strait ice edge

    Labels: Original floe, Fram Strait

    By late July, the original drifting floe and instrument network reached the Fram Strait region near the marginal ice zone (the transition area between open ocean and pack ice). This effectively ended the first major drift phase and brought melt-season processes to a head, including rapid floe breakup. The early arrival highlighted how dynamic and thin the sea-ice pack was during the MOSAiC year.

  11. Polarstern reaches the North Pole during final stage

    Labels: Polarstern, North Pole

    During the final phase, Polarstern reached the North Pole after sea-ice conditions allowed unusually fast travel. This milestone supported late-season science focused on the end of summer melt and the beginning of refreezing. It also provided a high-profile reference point for communicating the expedition’s broader purpose: better observing the Arctic system that influences global climate and weather.

  12. Second ice camp established to complete full-year cycle

    Labels: Floe 2, ice camp

    To capture the crucial transition back toward freeze-up, Polarstern moved north and set up a new camp (often called “floe 2.0”) after the first floe’s breakup. The new camp allowed continued oceanography and sea-ice measurements as autumn approached, including the start of new ice growth. This step “closed the loop” scientifically by returning to fall-like conditions similar to the expedition’s start.

  13. Polarstern leaves floe 2.0 as field campaign winds down

    Labels: Floe 2, camp closure

    After roughly a month of observations on the second floe, operations on floe 2.0 ended as the expedition prepared to return to port. Ending on-ice work required carefully recovering instruments and closing down the camp to avoid leaving equipment behind. This transition marked the shift from field measurements to the long process of data processing and scientific synthesis.

  14. Polarstern returns to Bremerhaven, ending expedition

    Labels: RV Polarstern, Bremerhaven

    RV Polarstern arrived back in Bremerhaven, Germany, completing the expedition’s field phase after more than a year of Arctic operations. The return marked a clear endpoint for the drifting observatory concept: a full annual cycle of coordinated measurements through autumn, winter polar night, spring, and summer melt. The expedition’s legacy is its unusually comprehensive dataset designed to improve understanding and modeling of Arctic sea ice and its role in the global climate system.

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MOSAiC expedition: Multidisciplinary drifting observatory for Arctic climate (2019–2020)