Vertical mixing of upper water masses in Arctic fjords is important for circulation and transport of nutrients and heat. However, the distribution of turbulent mixing is poorly known. Here we present hydrographic and microscale turbulence measurements from six fjords in Northwestern (69°N–75°N) Greenland. Water mass distributions showed the presence of warm bottom water of Atlantic origin in all fjord transects and a significant modification of upper water masses in fjords with tidewater outlet glaciers. Spatial and temporal distribution of turbulence in the fjords showed, in general, low rates of turbulent kinetic energy, ε (∼10⁻⁹ W kg⁻¹), and strong stratification implies that vertical exchange in the upper ∼200 m was relatively weak. However, measurements within 2 km of the terminus of a tidewater outlet glacier showed values of ε and inferred turbulent diffusion coefficients >10⁻⁴ m² s⁻¹ that were about two orders of magnitude larger than elsewhere in the deep fjords. This elevated mixing corresponded to comparatively large heat and salt fluxes. These observations suggest that vertical mixing near tidewater outlet glaciers results in localized mixing hot spots, likely due to subglacial discharge and near-glacial current shear, that contribute significantly to vertical exchange in the deep fjords.

中文翻译：

---

格陵兰岛西北部潮水出口冰川附近分层峡湾的垂直混合

北极峡湾上层水团的垂直混合对于营养物质和热量的循环和运输很重要。然而，湍流混合的分布知之甚少。在这里，我们展示了格陵兰岛西北部 (69°N–75°N) 六个峡湾的水文和微尺度湍流测量结果。水团分布显示，所有峡湾横断面都存在源自大西洋的温暖底层水，并且在有潮水出口冰川的峡湾中，上层水团发生了显着变化。峡湾湍流的时空分布显示，一般而言，湍流动能 ε (∼10 ^-9  W kg ^-1)，强分层意味着上部~200 m 的垂直交换相对较弱。然而，在距潮水出口冰川终点 2 公里范围内的测量结果显示，ε 值和推断的湍流扩散系数 >10 ^-4  m ² s ^-1比深峡湾中的其他地方大两个数量级左右。这种提高的混合对应于相对较大的热和盐通量。这些观察结果表明，潮水出口冰川附近的垂直混合导致局部混合热点，这可能是由于冰下排放和近冰流剪切，这对深峡湾的垂直交换有显着贡献。