Ocean glider observations in Greater Cook Strait, New Zealand

Continuous, long-duration and high resolution hydrographic sampling from gliders have enabled the evaluation of variability in density structure of submesoscale features in a New Zealand shelf sea. Glider sampling allows for: 1) minimal disturbance of upper stratification and 2) horizontal and temporal spacing between profiles to be typically less than one kilometer and 30 minutes depending on the profile depth. Seven glider surveys were completed from 2015 to 2018. The average glider track spanned 132 40o75S, 174o49E to 39o91S, 171o90E. In each survey, the glider transverses from east to west and back to its deployment location. For surveys 3, 4, 6, 9 and 11, the glider was deployed closer to the Cook Strait Narrows. As the glider would spend multiple days trying to overcome strong currents due to strong tidal fluctuations near the Narrows, deployments for surveys 12 and 15 were from Tasman Bay to maximise observations across the Greater Cook Strait shelf sea. This study used Teledyne Webb Research Slocum G2 gliders equipped with Seabird CTD sensor, Aanderaa Oxygen Optode and Wet Labs Environmental Characterization Optics (ECO) puck, that measured chlorophyll-a fluorescence, backscatter (at 470, 532, 660 and 700 nm) and chromophoric dissolved organic matter (CDOM). Temperature, conductivity, and pressure data were sampled at 0.5 Hz, and subsequently processed to remove spikes. The accuracy within calibration range of temperature and conductivity were +/-0.002oC and +/-0.0003 S m-1, respectively. Glider data processing was completed using the SOCIB glider toolbox (https://github.com/socib/glider_toolbox; Troupin et al. (2015)). Glider data processing includes salinity lag correction for the thermal lag error for the un-pumped CTD unit. Data were averaged in vertical bins of 1 m.

水下滑翔机的连续、长时、高分辨率水文采样，使得评估新西兰陆架海中尺度下特征（submesoscale features）密度结构的变异性成为可能。滑翔机采样具备以下特点：1）对上层分层的干扰极小；2）剖面间的水平间距与时间间隔通常小于1公里和30分钟（具体取决于剖面深度）。2015年至2018年间完成了7次滑翔机调查。平均滑翔机航迹覆盖范围为南纬40.75°、东经174.49°至南纬39.91°、东经171.90°。每次调查中，滑翔机均从东向西横穿，再返回其部署位置。在第3、4、6、9和11次调查中，滑翔机的部署位置更靠近库克海峡狭窄段（Cook Strait Narrows）。由于滑翔机在狭窄段附近需耗费数日克服由强潮汐波动引发的强劲海流，因此第12和15次调查将滑翔机部署于塔斯曼湾（Tasman Bay），以最大化对大库克海峡陆架海（Greater Cook Strait shelf sea）的观测覆盖。本研究使用的Teledyne Webb Research Slocum G2滑翔机配备了Seabird CTD传感器、Aanderaa氧气光极（Oxygen Optode）及Wet Labs环境特征光学（Environmental Characterization Optics, ECO）探头，可测量叶绿素a荧光、后向散射（波长470、532、660和700 nm）以及有色溶解有机物（chromophoric dissolved organic matter, CDOM）。温度、电导率和压力数据的采样频率为0.5 Hz，随后经过处理以去除尖峰信号。温度和电导率在校准范围内的精度分别为±0.002℃和±0.0003 S/m。滑翔机数据处理通过SOCIB滑翔机工具箱（https://github.com/socib/glider_toolbox；Troupin等，2015）完成。滑翔机数据处理包括针对非泵式CTD单元热滞后误差的盐度滞后校正。数据在1米的垂直区间内进行平均处理。