The Hudson Bay system is undergoing climate-driven changes in sea ice and freshwater inflow and has seen an increase in winter river inflow since the 1960s due in part to flow regulation for hydropower production. Southeast Hudson Bay and adjacent James Bay are at the forefront of these changes, with more than 1-month shortening of the season of sea ice cover as defined using satellite data, increases in winter inflow from the regulated La Grande River complex, and changes in coastal ice and polynya behavior described by Belcher Islands’ Inuit. In summer, there is a fresh coastal domain in southeast Hudson Bay fueled by river runoff and sea ice melt. To investigate winter oceanographic conditions and potential interactions between runoff and ice melt or brine in southeast Hudson Bay, we initiated the first winter study of the shallow waters surrounding the Belchers, collecting conductivity-temperature-depth (CTD) profiles and conductivity-temperature (CT) time series using under-ice moorings, and collecting water samples and ice cores during four campaigns between January 2014 and March 2015. Tandem measurements of salinity and δ¹⁸O were made for the water and ice samples to discriminate between freshwater sources (river runoff and sea ice melt). We find that southeast Hudson Bay, and particularly the nearshore domain southeast of the Belchers, is distinguished in winter by the presence of river water and strong surface stratification, which runs counter to expectations for a system in which local freshwater remains frozen on land until spring freshet (May–June) and sea ice growth is adding brine to surface waters. The amount of river water around the Belcher Islands increased significantly from fall through to late winter according to δ¹⁸O records of ice. The accumulation of river water in surface waters during the winter is directly associated with an accumulation of brine, which considerably exceeds the capacity of local ice formation to produce brine. We therefore infer that brine is advected into the study area together with river water, and that interplay between these properties establishes and maintains the level of surface stratification throughout winter. With reference to a NEMO ocean model simulation of winter circulation in the study area, we propose a conceptual model in which winter river inflow into James Bay drives the northward transport of both river water and brine captured near the surface, with reductions in brine-driven deep convection in the area’s flaw leads. While past changes in winter oceanographic conditions and sea ice cannot be reconstructed from the few available scientific data, the presence of significant runoff in winter in southeast Hudson Bay implies heightened sensitivity to delayed freeze-up under a warmer climate, which will have the effect of reducing brine early in the winter, also promoting increased stratification and river plume transport.

中文翻译：

---

哈德逊湾东南部冬季河流径流和海冰排除在控制分层中的作用

自1960年代以来，哈德逊湾（Hudson Bay）系统正经历着气候驱动的海冰和淡水流入变化，冬季河流的流入量有所增加，部分原因是水力发电的流量调节。东南哈德逊湾和邻近的詹姆斯湾处于这些变化的最前沿，根据卫星数据定义，海冰覆盖季节缩短了1个月以上，受管制的拉格兰德河综合体的冬季流入量增加，并且Belcher Islands的因纽特人描述的沿海冰和波利尼亚行为。夏季，哈德逊湾东南部有一个新鲜的沿海地区，其河流径流和海冰融化助长了该地区。为了调查哈德逊湾东南部的冬季海洋条件以及径流与融冰或盐水之间的潜在相互作用，对水和冰样品进行了¹⁸ O的区分，以区分淡水来源（河流径流和海冰融化）。我们发现东南哈德逊湾，特别是Belchers东南近岸地区，在冬季以河水和强烈的地层分层为特征，这与人们对当地淡水保持冻结直到春季的系统的期望背道而驰。淡水（5月至6月）和海冰的生长正在向地表水中添加盐水。周围的贝尔彻群岛河水量显著下跌，从通过按照δ增加至冬末¹⁸O记录冰。冬季，地表水中河水的积聚与盐水的积聚直接相关，而盐水的积聚大大超过了当地冰层形成盐水的能力。因此，我们推断盐水与河水一起被平流到研究区域，并且这些属性之间的相互作用建立并维持了整个冬季的地表分层水平。参照研究区域冬季环流的NEMO海洋模型模拟，我们提出了一个概念模型，其中冬季河流流入詹姆斯湾，驱使在表层附近捕获的河水和盐水向北输送，同时减少了盐水驱动该区域缺陷对流的深度对流。