Abstract
Abstract. In recent decades, Arctic sea ice has shifted toward a younger, thinner, seasonal ice regime. Studying and understanding this “new” Arctic will be the focus of a year-long ship campaign beginning in autumn 2019. Lagrangian tracking of sea ice floes in the Community Earth System Model Large Ensemble (CESM-LE) during representative “perennial” and “seasonal” time periods allows for understanding of the conditions that a floe could experience throughout the calendar year. These model tracks, put into context a single year of observations, provide guidance on how observations can optimally shape model development, and how climate models could be used in future campaign planning. The modeled floe tracks show a range of possible trajectories, though a Transpolar Drift trajectory is most likely. There is also a small but emerging possibility of high-risk tracks, including possible melt of the floe before the end of a calendar year. We find that a Lagrangian approach is essential in order to correctly compare the seasonal cycle of sea ice conditions between point-based observations and a model. Because of high variability in the melt season sea ice conditions, we recommend in situ sampling over a large range of ice conditions for a more complete understanding of how ice type and surface conditions affect the observed processes. We find that sea ice predictability emerges rapidly during the autumn freeze-up and anticipate that process-based observations during this period may help elucidate the processes leading to this change in predictability.
Highlights
In recent decades, sea ice in the Arctic Ocean has undergone rapid change (Serreze and Stroeve, 2015; Stroeve and Notz, 2018)
While both the seasonal and perennial Community Earth System Model Large Ensemble (CESM-LE) mean track distances are longer than the satellite-derived tracks, seasonal tracks tend to travel further than perennial tracks (Table 1)
As an initial condition ensemble, the Community Earth System Model (CESM)-LE is a tool designed to explore the effects of internal climate variability and forced change
Summary
Sea ice in the Arctic Ocean has undergone rapid change (Serreze and Stroeve, 2015; Stroeve and Notz, 2018). Passive microwave satellite observations since 1979 show that Arctic sea ice extent has decreased in all months, and the 12 lowest September sea ice extents were recorded in the past 12 years (Richter-Menge et al, 2019). Year-round in situ observations are critical for understanding the coupled air–sea–sea ice processes over the remote Arctic Ocean, but they pose enormous challenges. The Surface Heat Budget of the Arctic (SHEBA) project obtained year-round, process-based observations over sea ice when the Canadian Coast Guard icebreaker Des Groseilliers was frozen into the Beaufort Sea and drifted freely with the pack from October 1997 to October 1998 (Uttal et al, 2002).
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