Declining sea ice is expected to change the Arctic's physical and biological systems in ways that are difficult to predict. This study used stable isotope compositions (δ13C and δ15N) of archaeological, historic, and modern Pacific walrus (Odobenus rosmarus divergens) bone collagen to investigate the impacts of changing sea ice conditions on walrus diet during the last ~4000 yr. An index of past sea ice conditions was generated using dinocyst-based reconstructions from three locations in the northeastern Chukchi Sea. Archaeological walrus samples were assigned to intervals of high and low sea ice, and δ13C and δ15N were compared across ice states. Mean δ13C and δ15N values were similar for archaeological walruses from intervals of high and low sea ice; however, variability among walruses was greater during low-ice intervals, possibly indicating decreased availability of preferred prey. Overall, sea ice conditions were not a primary driver of changes in walrus diet. The diet of modern walruses was not consistent with archaeological low sea ice intervals. Rather, the low average trophic position of modern walruses (primarily driven by males), with little variability among individuals, suggests that trophic changes to this Arctic ecosystem are still underway or are unprecedented in the last ~4000 yr.

预计海冰的减少将以难以预测的方式改变北极的物理和生物系统。本研究使用考古、历史和现代太平洋海象 ( Odobenus rosmarus divergens ) 骨胶原的稳定同位素组成（δ 13 C 和 δ 15 N）来研究过去约 4000 年海冰条件变化对海象饮食的影响。使用来自楚科奇海东北部三个位置的基于恐龙的重建生成了过去海冰状况的指数。考古海象样本被分配到高海冰和低海冰的区间，并比较了冰态的 δ 13 C 和 δ 15 N。平均 δ 13 C 和 δ 15来自高海冰和低海冰间隔的考古海象的 N 值相似；然而，在低冰期，海象之间的变异性更大，这可能表明首选猎物的可用性降低。总体而言，海冰条件不是海象饮食变化的主要驱动力。现代海象的饮食与考古学的低海冰间隔不一致。相反，现代海象的低平均营养位置（主要由雄性驱动），个体之间几乎没有差异，这表明这个北极生态系统的营养变化仍在进行中，或者在过去约 4000 年中是前所未有的。