McKinney Paul, Austin Jay, Fai Gills
U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, 6201 Congdon Blvd., Duluth, MN 55804, USA.
Large Lakes Observatory and Department of Physics and Astronomy, University of Minnesota Duluth, Duluth, Minnesota, USA.
Limnol Oceanogr. 2019 May 1;64(3):1309-1322. doi: 10.1002/lno.11117.
Wind-driven turbidity plumes frequently occur in the western arm of Lake Superior and may represent a significant cross shelf transport mechanism for sediment, nutrient and biota. Here we characterize a plume that formed in late April 2016 using observations from in situ sensors and remote sensing imagery, and estimate the volume of cross shelf transport using both the observations and an idealized analytical model of plume formation. The steady-state, barotropic model is used to determine a relationship between the intensity and duration of a wind event and the volume of water transported from nearshore to offshore during the event. The model transport is the result of nearshore flow in the direction of the wind and a pressure-gradient-driven counter flow in the deeper offshore waters, consistent with observations. The volume of offshore transport associated with the 2016 plume is estimated by both methods to have been on the order of 10 m. Analysis of similar events from 2008-2016 shows a strong relationship between specific wind impulse and plume volume. Differences in the intensity and duration of individual events as well as ice cover, which prevents plume formation, lead to interannual variability of offshore transport ranging over an order of magnitude and illustrates how wind-driven processes may contribute to interannual variability of ecosystem functioning.
风生浊流羽流经常出现在苏必利尔湖的西部水域，可能是沉积物、营养物质和生物群跨陆架输运的重要机制。在此，我们利用原位传感器的观测数据和遥感影像，对2016年4月下旬形成的一股羽流进行了特征描述，并使用观测数据和羽流形成的理想化分析模型估算了跨陆架输运的量。稳态正压模型用于确定风事件的强度和持续时间与事件期间从近岸向近海输运的水量之间的关系。模型输运是近岸水流沿风向流动以及较深近海区域由压力梯度驱动的反向水流的结果，这与观测结果一致。两种方法估算出与2016年羽流相关的近海输运量约为10立方米。对2008 - 2016年类似事件的分析表明，特定风冲量与羽流体积之间存在很强的关系。个别事件的强度和持续时间以及阻止羽流形成的冰盖的差异，导致近海输运的年际变化范围超过一个数量级，说明了风生过程可能如何导致生态系统功能的年际变化。
