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Physical Controls on the Macrofaunal Benthic Biomass in Barrow Canyon, Chukchi Sea
Journal of Geophysical Research: Oceans ( IF 3.6 ) Pub Date : 2021-04-15 , DOI: 10.1029/2020jc017091
Robert S. Pickart 1 , Michael A. Spall 1 , Peigen Lin 1 , Frank Bahr 1 , Leah T. McRaven 1 , Kevin R. Arrigo 2 , Jacqueline M. Grebmeier 3
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A region of exceptionally high macrofaunal benthic biomass exists in Barrow Canyon, implying a carbon export process that is locally concentrated. Here we offer an explanation for this benthic “hotspot” using shipboard data together with a set of dynamical equations. Repeat occupations of the Distributed Biological Observatory transect in Barrow Canyon reveal that when the northward flow is strong and the density front in the canyon is sharp, plumes of fluorescence and oxygen extend from the pycnocline to the seafloor in the vicinity of the hotspot. By solving the quasi‐geostrophic omega equation with an analytical flow field fashioned after the observations, we diagnose the vertical velocity in the canyon. This reveals that, as the along stream flow converges into the canyon, it drives a secondary circulation cell with strong downwelling on the cyclonic side of the northward flow. The downwelling quickly advects material from the pycnocline to the seafloor in a vertical plume analogous to those seen in the observations. The plume occurs only when the phytoplankton reside in the pycnocline, since the near‐surface vertical velocity is weak, also consistent with the observations. Using a wind‐based proxy to represent the strength of the northward flow and hence the pumping, in conjunction with a satellite‐derived phytoplankton source function, we construct a time series of carbon supply to the bottom of Barrow Canyon.

中文翻译:

楚科奇海巴罗峡谷大型动物底栖生物量的物理控制

巴罗峡谷(Barrow Canyon)中存在大量大型底栖生物,这意味着碳出口过程局部集中。在这里,我们使用船上数据和一组动力学方程式对底栖“热点”进行解释。对巴罗峡谷的分布式生物天文台样带的重复占领表明,当向北流动强烈并且峡谷中的密度锋线锋利时,荧光和氧气的羽状流从比多可可林一直延伸到热点附近的海底。通过用观测后形成的解析流场求解拟地转欧米伽方程,我们可以诊断峡谷中的垂直速度。这表明随着顺流汇入峡谷,它在向北流动的旋风侧驱动具有强烈下沉的二次循环单元。下行流以类似于观测中所见的垂直羽状迅速将物质从比考克林平移到海底。由于近地表垂直速度较弱,浮游生物仅在浮游生物驻留在碧容线中时才出现羽状流,这也与观测结果一致。利用基于风的代理来代表北向流动的强度,从而代表泵送,再结合卫星衍生的浮游植物源函数,我们构造了巴罗峡谷底部碳供应的时间序列。由于近地表垂直速度较弱,浮游生物仅在浮游生物驻留在碧容线中时才出现羽状流,这也与观测结果一致。利用基于风的代理来代表北向流动的强度,从而代表泵送,再结合卫星衍生的浮游植物源函数,我们构造了巴罗峡谷底部碳供应的时间序列。由于近地表垂直速度较弱,浮游生物仅在浮游生物驻留在碧容线中时才出现羽状流,这也与观测结果一致。利用基于风的代理来代表北向流动的强度,从而代表泵送,再结合卫星衍生的浮游植物源函数,我们构造了巴罗峡谷底部碳供应的时间序列。
更新日期:2021-05-05
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