Underwater frazil ice and its suspension depth detected from ADCP backscatter data around sea ice edge in the Sea of Okhotsk
Underwater frazil ice and its suspension depth detected from ADCP backscatter data around sea ice edge in the Sea of Okhotsk
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DOI：
10.1016/j.coldregions.2021.103382
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发表时间：
2021-09-21
影响因子：
4.1
通讯作者：
Kikuchi, Takashi
中科院分区：
文献类型：
--
作者：
Ito, Masato;Ohshima, Kay I.;Kikuchi, Takashi
小的海洋冰晶，即所谓的frazil冰，是在水柱中最初的冰形成过程中产生的。在湍流条件下，冰可以悬浮，并且它可以通过与再悬浮的沉积物相互作用来吸收颗粒物。本研究探讨了悬浮深度的frazil冰从150 kHz的声学多普勒海流剖面仪（ADCPs）的后向散射数据的基础上停泊在库页岛以东的鄂霍次克海的深海区域，从800至1700米的底部深度在1998 - 2000年。ADCP后向散射强度揭示了浮游动物昼夜垂直迁移的主导信号。此外，从表面延伸到水柱中的悬浮冰柱增强了后向散射。在海冰季节，在每个系泊点多次检测到冰。这些事件发生在系泊地点位于海冰区域边缘且风速较高（通常超过8 m/s）时。只要使用深度大于-15米的有效ADCP后向散射数据，冰碛的估计平均悬浮深度为35米。最大悬浮深度达-100 m，比以往各海冰区报道的深得多，这是因为冰是由大气在表面吸收热量而形成的。这些结果表明，冰碛冰与底部接触，并在较浅的区域清除海底沉积物，导致将沉积物来源的常量营养元素纳入海冰，这将在生物相关的物质循环中发挥重要作用。
Small sea ice crystals, so-called frazil ice, are created during initial ice formation in the water column. Frazil ice can be suspended under turbulent conditions, and it can scavenge particulate matter through interaction with resuspended sediment. This study examined the suspension depth of frazil ice based on backscatter data from 150-kHz Acoustic Doppler Current Profilers (ADCPs) moored in the pelagic regions east of Sakhalin Island in the Sea of Okhotsk with bottom depths from 800 to 1700 m during 1998-2000. ADCP backscatter strength revealed dominant signals from the diurnal vertical migration of zooplankton. In addition, the backscatter was enhanced by suspended frazil ice that extended down the water column from the surface. Frazil ice was detected several times at each mooring site during sea-ice seasons. These events occurred when the mooring sites were on the edge of the sea ice regions and the wind speed was high, typically exceeding 8 m/s. The estimated mean suspension depth of frazil ice was 35 m as long as valid ADCP backscatter data from depths greater than -15 m were used. The maximum suspension depth reached -100 m, which was much deeper than that previously reported in various sea-ice regions as frazil ice originating from the atmospheric heat absorption at the surface. These results suggest that frazil ice comes into contact with the bottom and scavenges seafloor sediment in shallower regions, resulting in incorporation of sediment-origin macronutrients into sea ice, which would play an important role in bio-related material cycle.