We present the first observational-based assessment of the seasonal circulation and volume transport driven by the Bransfield Current (BC), a surface-intensified coastal jet which flows northeastward along the southern slope of the South Shetland Islands (SSI) in the Bransfield Strait (BS). To this aim, we construct a seasonal climatology based on an extensive dataset of direct velocity measurements which were routinely collected along ship tracks from 375 cruises between 1999 and 2014. A major finding is that the BC is a year-round feature of the circulation in the BS, flowing persistently towards the northeast along the southern slope of the SSI. Along its full path, core velocities of the BC deepen down to at least 200–250 m depth. Maximum velocities are found to reach 60 cm s⁻¹ during summer, and 40 cm s⁻¹ during autumn and spring. Available measurements confirm the BC also flows northeastward during wintertime, at least from Nelson Island to King George Island, with maximum core velocities about 40 cm s⁻¹. The spatial variability along the SSI shelf suggests two distinct regions for the BC: a narrower jet of ∼20–30 km upstream of Nelson Strait, and a wider jet of ∼40 km downstream. Upstream of Nelson Strait, the BC transports about 0.93 ± 0.15 Sv in summer, 0.88 ± 0.19 Sv in autumn and 0.65 ± 0.13 Sv in spring. Available observations during winter lead to weaker transports about 0.50 ± 0.04 Sv from Greenwich Island to Nelson Strait. Downstream of Nelson Strait, volume transport estimates show no significant differences among seasons being on average 1.31 ± 0.20 Sv. As compared to upstream of Nelson Strait, the year-round average volume transport is weaker and about 0.74 ± 0.13 Sv. A mass balance analysis supports that this downstream increase in volume transport is likely due to a recurrent inflow passing through Nelson Strait and feeding the BC with source waters coming from the northern slope of the SSI. These results highlight that future observational efforts must focus on assessing the seasonal hydrography of the BC with mesoscale-solving measurements, especially when noting that the BC has been shown in the past to behave as a summertime buoyancy-driven coastal jet driving relatively warm and fresh Transitional Zonal Water with Bellingshausen influence (TBW), whose presence in the BS might be limited during winter.

我们首次对由布兰斯菲尔德海流 (BC) 驱动的季节性环流和体积输送进行了基于观测的评估，这是一种沿布兰斯菲尔德海峡南设得兰群岛 (SSI) 南坡向东北流动的表面强化沿海急流。 BS）。为此，我们基于广泛的直接速度测量数据集构建了季节性气候学，这些数据集在 1999 年至 2014 年期间从 375 次航行中沿船轨定期收集。一个主要发现是，BC 是环流的全年特征。 BS，沿着 SSI 的南坡持续向东北流动。沿着其完整路径，BC 的核心速度加深到至少 200-250 m 深度。发现最大速度在夏季达到 60 cm s ^{-1和 40 cm s-1}在秋季和春季。现有测量结果证实，BC 在冬季也向东北流动，至少从尼尔森岛流向乔治王岛，最大核心速度约为 40 cm s ^-1. 沿 SSI 陆架的空间变化表明 BC 有两个不同的区域：纳尔逊海峡上游 20-30 公里的较窄射流和下游 40 公里的较宽射流。尼尔森海峡上游，BC 在夏季输送约 0.93 ± 0.15 Sv，秋季输送约 0.88 ± 0.19 Sv，春季输送约 0.65 ± 0.13 Sv。冬季可用的观测结果导致从格林威治岛到尼尔森海峡的传输减弱约 0.50 ± 0.04 Sv。在尼尔森海峡下游，运输量估计显示季节之间没有显着差异，平均为 1.31 ± 0.20 Sv。与尼尔森海峡上游相比，全年平均运量较弱，约为 0.74 ± 0.13 Sv。质量平衡分析支持，这种下游体积输送的增加可能是由于反复流入通过纳尔逊海峡并用来自 SSI 北坡的源水喂养 BC。这些结果表明，未来的观测工作必须侧重于通过中尺度求解测量来评估 BC 的季节性水文，特别是当注意到 BC 过去已被证明表现为夏季浮力驱动的沿海喷气机，驾驶相对温暖和新鲜时受贝林斯豪森影响的过渡带状水域 (TBW)，其在 BS 中的存在在冬季可能会受到限制。