Deep-sea currents in the Northeast Pacific Ocean are examined using observations at Station M, located on the abyssal plain 220 km offshore of central California. Collected near the seabed at ~4000 m depth from October 2014–October 2018, the current meter observations supplement long-term investigations of deep-sea benthic ecology at this site. To investigate mechanisms for variability at different time scales, the observed currents are separated into low-frequency fluctuations with periods of 1.4–60 days, fluctuations that are coherent with astronomical tidal forcing, and other high-frequency fluctuations. These motions contribute similarly to the overall variability at this location. Low-frequency currents exhibit elevated energy at periods of ~30 days, consistent with previous observations elsewhere in the abyssal North Pacific. However, unlike some other observations in the deep ocean, there is no consistent seasonal cycle in the variability of low-frequency motion. The theoretical prediction of Sverdrup balance between transport and local wind stress curl does not explain the timing or the magnitude of low frequency currents, suggesting that they are driven by remote winds or eddy dynamics. The non-tidal high-frequency fluctuations show evidence of a near-inertial peak and clockwise rotary motion, consistent with theoretical expectations for the internal gravity wave spectrum. Like the low-frequency currents, interannual variability of internal wave energy appears to be stronger than seasonal variability. Observations of the vertical structure 2.5–17.5 m above bottom are used to characterize the interactions between currents and the seabed. Observational estimates of diurnal and semidiurnal tidal ellipses are consistent with results from an analytical model that incorporates the effects of the Earth's rotation and tidal acceleration. A numerical model of the time dependent boundary layer provides estimates of bottom roughness and friction velocity that are consistent with previous observations at this site. This study shows that the strength, time scale and polarization of the near-bottom currents at Station M vary significantly between years, demonstrating the value of multi-year records in studies of the lateral transport of organic matter, sediment and organisms at this abyssal site.

东北太平洋的深海洋流使用M站的观测数据进行了检查，M站位于加利福尼亚中部深海220公里处的深海平原上。从2014年10月至2018年10月，该海表收集于海床附近，深度约4000 m，目前的观测值补充了对该地点深海底栖生态的长期调查。为了研究不同时间尺度上的变化机制，将观测到的电流分为1.4–60天的低频波动，与天文潮汐强迫相一致的波动以及其他高频波动。这些运动对这个位置的整体变化有相似的贡献。低频电流在约30天的时间内显示出较高的能量，这与深海北部太平洋其他地方的先前观测结果一致。然而，与深海中的其他一些观测结果不同，低频运动的变异性没有一致的季节性周期。在运输和局部风应力卷曲之间的Sverdrup平衡的理论预测不能解释低频电流的时间或大小，这表明它们是由远程风或涡流动力学驱动的。非潮汐高频波动显示出接近惯性的峰值和顺时针旋转运​​动的证据，这与内部重力波谱的理论预期一致。像低频电流一样，内部波能的年际变化似乎比季节变化要强。底部上方2.5–17.5 m的垂直结构的观测值用于表征洋流与海床之间的相互作用。昼夜和半日潮汐椭圆的观测估计与分析模型的结果一致，该模型综合了地球自转和潮汐加速度的影响。随时间变化的边界层的数值模型可提供底部粗糙度和摩擦速度的估算值，这些估算值与该位置以前的观测结果一致。这项研究表明，M站附近海流的强度，时间尺度和极化在几年之间存在显着变化，这证明了多年记录在该深海地区有机物，沉积物和生物体横向运输研究中的价值。 。随时间变化的边界层的数值模型可提供底部粗糙度和摩擦速度的估算值，这些估算值与该位置以前的观测结果一致。这项研究表明，M站附近海流的强度，时间尺度和极化在几年之间存在显着变化，这证明了多年记录在该深海地区有机物，沉积物和生物体横向运输研究中的价值。 。随时间变化的边界层的数值模型可提供底部粗糙度和摩擦速度的估算值，这些估算值与该位置以前的观测结果一致。这项研究表明，M站附近海流的强度，时间尺度和极化在几年之间存在显着变化，这证明了多年记录在该深海地区有机物，沉积物和生物体横向运输研究中的价值。 。