Fig. 3

Comparison between our dataset and ship-based observations³⁵. (a) Ice and open-water regimes in the course from DEEP-AA and observations. The band along the top comes from DEEP-AA. The light grey blocks indicate the ship was not in a polynya; black ones indicate that it was in the Terra Nova Bay polynya (TNBP); green ones indicate that it was in the Ross Sea polynya (RSP); and blue ones refer to the open sea. The onboard observed ice and polynya regimes are marked below the band; MIZ indicates the marginal ice zone, and FYI indicates first-year ice. All of them come from the PIPERS report in Ackley et al.³⁵. The time of entry or exit from the polynya is also marked in (b) with dotted lines. In (b), the blue line shows the ice thickness from the ship-based observations; the blue shaded areas highlight where the ice was thinner than 10 cm (i.e., where the blue line is below the grey dashed line), and the underway wide break is marked by the blue inverted triangle. The red line shows the distance from the ship to the polynyas found by our dataset. The ship trajectory is shown in Supplementary Figure 5.