Intermittent Intense Turbulent Mixing under Ice in the Laptev Sea Continental Shelf
Intermittent Intense Turbulent Mixing under Ice in the Laptev Sea Continental Shelf
复制标题
DOI：
10.1175/2010jpo4425.1
复制
发表时间：
2011-03-01
影响因子：
3.5
通讯作者：
Hoelemann, Jens
中科院分区：
文献类型：
--
作者：
Lenn, Yueng-Djern;Rippeth, Tom P.;Hoelemann, Jens
拉普特夫海底部边界层和跃层的垂直混合是根据2008年10月在100%海冰下收集的微结构温度、电导率和剪切观测的快速采样12小时时间序列来评估的。当模拟潮流指向坡面时，底边界湍动能耗散增强(epsilon类似于10(-4)Wm(-3))，超过背景高度(epsilon类似于10(-6)Wm(-3))，并延伸到海床以上10m。沿拉普特夫海海床盐跃层类水域的向上热通量达到峰值，接近4-8Wm(-2)，在12h采样期间平均接近2Wm(-2)。在Laptev海跃层中，观测到了一个孤立的2小时强度耗散事件(epsilon类似于10(-3)Wm(-3))和垂直扩散系数，这不是局部性风事件的线索。停泊在拉普特夫海中部靠近M-2临界纬度的声学多普勒海流仪的观测结果与以前的模型一致，在该模型中，混合幕是由旋转的跃层切变矢量与冰下应力矢量对齐导致的顺跃层切变的增强而驱动的。来自北极盐跃层的向上交叉跃层热通量的峰值接近54Wm(-2)，12h平均值接近12Wm(-2)。这些结果突出了北冰洋陆架海洋混合过程的间歇性，以及这些过程如何影响北冰洋水团的转变。观测还清楚地表明，海冰的存在或不存在对近惯性动能的可获得性产生深远影响，以推动北极大陆架上的垂直混合。
Vertical mixing in the bottom boundary layer and pycnocline of the Laptev Sea is evaluated from a rapidly sampled 12-h time series of microstructure temperature, conductivity, and shear observations collected under 100% sea ice during October 2008. The bottom boundary turbulent kinetic energy dissipation was observed to be enhanced (epsilon similar to 10(-4) W m(-3)) beyond background levels (epsilon similar to 10(-6) W m(-3)), extending up to 10 m above the seabed when simulated tidal currents were directed on slope. Upward heat fluxes into the halocline-class waters along the Laptev Sea seabed peaked at similar to 4-8 W m(-2), averaging out to similar to 2 W m(-2) over the 12-h sampling period. In the Laptev Sea pycnocline, an isolated 2-h episode of intense dissipation (epsilon similar to 10(-3) W m(-3)) and vertical diffusivities was observed that was not clue to a localized wind event. Observations from an acoustic Doppler current meter moored in the central Laptev Sea near the M-2 critical latitude are consistent with a previous model in which mixing episodes are driven by an enhancement of the pycnocline shear resulting from the alignment of the rotating pycnocline shear vector with the under-ice stress vector. Upward cross-pycnocline heat fluxes from the Arctic halocline peaked at similar to 54 W m(-2), resulting in a 12-h average of similar to 12 W m(-2). These results highlight the intermittent nature of Arctic shelf sea mixing processes and how these processes can impact the transformation of Arctic Ocean water masses. The observations also clearly demonstrate that absence or presence of sea ice profoundly affects the availability of near-inertial kinetic energy to drive vertical mixing on the Arctic shelves.