R/V Mirai Cruise MR15-03

In this cruise, to examine physical and chemical characteristics of an eddy that contains the Pacific-origin summer water in an area around the Barrow Canyon off the coast of Alaska, and to study the temporal variation of the eddy and its impact on the lower-trophic level ecosystem, we conducted ship-based observations of ADCP, TurboMAP (turbulent measurements), PRR (underwater spectral irradiance and radiance measurements), CTD/water samplings, XCTD, UCTD, GPS drifting buoys, and plankton nets. We also deployed a sediment trap in this area to investigate particle transports by the eddy. Furthermore, we recovered and re-deployed moorings to estimate transports of the Pacific-origin summer and winter waters and the associated heat and freshwater (salt) fluxes, and to study their seasonal variations. On the other hand, in an area around the Hanna Canyon, a downstream area of the eddy passage, we conducted ship-based observations of TurboMAP (turbulent measurements), PRR (underwater spectral irradiance and radiance measurements), CTD/water samplings, and plankton nets to examine physical and chemical characteristics of the water there and distributions of phyto- and zooplanktons. Another sediment trap was deployed in this area to study the spatial variation of particles with the migration of the eddy. This area is also located in a passage of the Pacific-origin winter water. Thus, the sediment trap may capture the seasonal variation and an eddy formation of the winter water. In the Chukchi Sea, we set an observation line along the 168.75W meridian near the U.S.-Russia border from the Bering Strait to the shelf slope. Along this line, we conducted ship-based observations of TurboMAP (turbulent measurements), PRR (underwater spectral irradiance and radiance measurements), CTD/water samplings, and plankton nets to examine physical and chemical characteristics of waters and wide-area distributions of phyto- and zooplanktons from a biological hotspot in the southern Chukchi Sea, where is one of the most biologically productive regions of the world's oceans, to a lower productive region in the northern end of the sea. Along the cruise track, we performed observations of radiosonde, Doppler radar, general meteorology, air sampling, sky radiometer, MAX-DOAS (Multi-Axis-Differential Optical Absorption Spectroscopy), disdrometers, sea surface water monitoring, sea bottom topography, gravity, and magnetic fields. In addition, magnetic total force intensity was measured by towing an instrument, Cesium precession magnetometer, in the North Pacific Ocean. Note that the field experiment in an area off the coast of Siberia, where the data are extremely scarce, was canceled due to a heavy sea ice condition.本次巡航旨在考察阿拉斯加沿岸巴罗峡谷（Barrow Canyon）周边海域内一道携带有太平洋夏季水的涡旋的物理化学特性，研究该涡旋的时间演化及其对低营养级生态系统的影响。为此我们开展了多类船载观测：包括声学多普勒流速剖面仪（ADCP）、湍流测量系统（TurboMAP）、水下光谱辐照度与辐亮度测量系统（PRR）、CTD/水体采样、XCTD、UCTD、GPS漂流浮标以及浮游生物网。同时在该海域部署了沉积物捕获器，以探究涡旋驱动的颗粒物输运过程。此外，我们回收并重新部署了锚系设备，用于估算太平洋夏季水与冬季水的输运量及其伴随的热通量与淡水（盐）通量，并研究其季节变化特征。 另一方面，在涡旋途经的下游区域汉娜峡谷（Hanna Canyon）周边海域，我们同样开展了船载观测，涵盖TurboMAP、PRR、CTD/水体采样以及浮游生物网，以考察该海域水体的物理化学特性以及浮游植物与浮游动物的分布情况。该区域还部署了另一台沉积物捕获器，用于研究随涡旋迁移的颗粒物的空间分布变化。此处同时也是太平洋冬季水的途经通道，因此该沉积物捕获器可同步捕捉冬季水的季节变化与涡旋形成过程。 在楚科奇海（Chukchi Sea），我们沿白令海峡（Bering Strait）至陆坡的168.75°W经线设置了观测断面。沿该断面开展船载观测，包括TurboMAP、PRR、CTD/水体采样以及浮游生物网，以解析从楚科奇海南部生物热点区（全球海洋生物生产力最高的区域之一）至北部低生产力海域的水体物理化学特性，以及浮游植物与浮游动物的广域分布特征。 沿本次巡航航迹，我们还开展了无线电探空、多普勒雷达、常规气象观测、大气采样、天空辐射计、多轴差分吸收光谱仪（MAX-DOAS）、雨滴谱仪、表层海水监测、海底地形测量、重力场观测以及磁场观测。此外，在北太平洋海域，我们通过拖曳铯旋进磁力仪（Cesium precession magnetometer），测量了地磁总强度。 值得注意的是，原计划在数据极度匮乏的西伯利亚沿岸海域开展的野外实验，因海冰厚重条件而取消。