Temporal variability in currents and the benthic boundary layer at an abyssal station off central California
Temporal variability in currents and the benthic boundary layer at an abyssal station off central California
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DOI：
10.1016/s0967-0645(97)00095-7
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发表时间：
1998-01-01
影响因子：
3
通讯作者：
Baldwin, R
中科院分区：
文献类型：
--
作者：
Beaulieu, S;Baldwin, R
1993 年至 1996 年间，在加州中部附近的一个深海站（Sta. M；深度 4100 米）收集了七个连续系泊点的当前仪表记录。分析了底部以上 600、50 和 2.5 m（海底边界层上方、顶部附近和内部）的整个 2 1/4 年流量时间序列，以获取平均流量统计数据以及潮下和潮汐变化。每个高度的平均水流矢量向南移动 < 1 cm s(-1)，但与零没有显着差异。光谱分析揭示了流动中的能量中尺度和季节性振荡，由 50-175 天周期的主轴震级峰值表明。潮汐（主要是半日潮汐）和惯性强迫导致流量变化，并影响为每个记录计算的平均主轴方向。最高流速记录在距底部50 m处（平均3.8 cm s(-1)；最大18.2 cm s(-1)）。对这个高度的月平均水流矢量的检查表明，在流速最高的月份（1994年4月、1995年和1994年10月），水流向南流动，在流速最低的月份（1994年7月和1995年8月），水流向北和向西。在2 1/4年期间间歇性收集的光传输和位温剖面图表明，Sta.1的底栖混合层在水流流速最高的月份（1994年7月和1995年8月）流向北部和西部。 M 平均延伸至底部以上 40 m（范围 15-80 mab）。最近沉积的碎屑局部重新悬浮的证据来自海底的延时照片，该照片显示一段近海底浑浊期与一段近海底高流量时期相对应。然而，摩擦速度的粗略估计表明，Sta 时的床应力通常太低。 M 引起沉积物局部再悬浮。我们假设观察到的底栖混合层含有从能量较高的区域平流到斯塔北部的悬浮颗粒。 M. (C) 1998 Elsevier Science Ltd. 保留所有权利。
Current meter records from seven sequential moorings were collected during 1993-1996 at an abyssal station off central California (Sta. M; 4100 m depth). The entire 2 1/4-yr time series of the flow at 600, 50, and 2.5 m above bottom (above, near the top of, and within the benthic boundary layer) were analyzed for mean flow statistics and subtidal and tidal variability. The mean current vectors at each altitude were southward at < 1 cm s(-1), although not significantly different from zero. Spectral analysis revealed energetic mesoscale and seasonal oscillations in the flow, indicated by peaks in principal axis magnitudes at periods of 50-175 days. Tidal (mainly semidiurnal) and inertial forcing contributed to flow variability and influenced the mean principal axis orientation calculated for each record. The highest flow speeds were recorded at 50 m above bottom (with an average of 3.8 cm s(-1); maximum 18.2 cm s(-1)). An examination of monthly-averaged current vectors at this altitude revealed that flow was to the south during the months of highest how speed (April 1994 and 1995 and October 1994) and to the north and west during the months of lowest flow speed (July 1994 and August 1995).Profiles of light transmission and potential temperature, collected intermittently during the 2 1/4-yr period, showed that the benthic mixed layer at Sta. M extended on average 40 m above bottom (range 15-80 mab). Evidence for local resuspension of recently deposited detritus came from time-lapse photographs of the sea floor that showed a period of near-bottom turbidity that corresponded to a period of high near-bottom flow. However, rough estimates of friction velocity indicated that the bed stress usually was too low at Sta. M to cause local resuspension of sediments. We hypothesize that the observed benthic mixed layers contained suspended particles advected from more energetic areas to the north of Sta. M. (C) 1998 Elsevier Science Ltd. All rights reserved.