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Open water in ice-covered oceans is an essential condition for shipping and resource exploitation. We investigate the interannual and spatial variations of the open water onset time in the Kara Sea (KS) and the underlying mechanisms through analyzing satellite-based observations and model simulation results. The empirical orthogonal function (EOF) analysis on the satellite sea ice concentration during 1979–2020 reveals two primary spatial distribution patterns of the open water onset time. The first mode EOF1 shows the coherent advance or delay of the open water onset time within the KS, which is consistent with the multiyear-averaged state. The second mode EOF2 exhibits a seesaw pattern between the southwest and middle regions, which represents the regional difference of the open water onset time within the KS. In 1997 with significant anomaly in EOF2, analysis of the model simulation reveals that the strong easterly wind-induced ice transport is the main reason for the earlier opening in the middle region and delayed opening in the southwestern region. When compared with the multiyear-averaged state, this dynamic process causes a noticeable redistribution of local sea ice in the early melting season (May to June), with much more ice in the southwestern region, thence influences the regional onset time of open water. A similar situation also occurred in the years 1985, 2001, and 2004, as these years presented stronger easterly wind energy accumulated over May to June, which cause earlier opening in the middle region and later opening in the southwestern region. Significance Statement: Variability of the open water in the Arctic Ocean has a significant impact on climate and ecosystem variability and also human activities. This study focuses on understanding why the onset time of open water was asynchronous over the Kara Sea. Generally, the open water first forms in the western region of the Kara Sea under the influences of warm inflow from the Barents Sea and river runoff. However, when strong easterly winds prevail across the whole region at the beginning of the melting season, sea ice is transported from east to west, resulting in the advanced opening in the middle and delayed opening in the southwest regions. This finding points out that wind can combine with surface and lateral heat fluxes to influence the interannual variability in the distribution of the open water onset time in the Kara Sea. [ABSTRACT FROM AUTHOR]

It is shown that the flag‐transitive, point‐primitive automorphism groups of 2‐(v,k,λ) $(v,k,\lambda)$ designs with λ $\lambda $ prime must be of affine type or almost simple type. [ABSTRACT FROM AUTHOR]

This paper contributes to the classification of flag-transitive symmetric 2- (v , k , λ) designs with λ prime. We investigate the structure of flag-transitive, point-quasiprimitive automorphism groups (G) of such 2-designs by applying the classification of quasiprimitive permutation groups. It is shown that the automorphism groups (G) have either an abelian socle or a non-abelian simple socle. Moreover, according to the classification of finite simple groups, we demonstrate that point-quasiprimitivity implies point-primitivity of G, except when the socle of G is P S L n (q) . [ABSTRACT FROM AUTHOR]