Estimating Water Transport from Short-Term Vessel-Based and Long-Term Bottom-Mounted Acoustic Doppler Current Profiler Measurements in an Arctic Lagoon Connected to the Beaufort Sea

Abstract

Acoustic Doppler current profilers (ADCP) are quasi-remote sensing instruments widely used in oceanography to measure velocity profiles continuously. One of the applications is the quantification of land–ocean exchange, which plays a key role in the global cycling of water, heat, and materials. This exchange mostly occurs through estuaries, lagoons, and bays. Studies on the subject thus require that observations of total volume or mass transport can be achieved. Alternatively, numerical modeling is needed for the computation of transport, which, however, also requires that the model is validated properly. Since flows across an estuary, lagoon, or bay are usually non-uniform and point measurements will not be sufficient, continuous measurements across a transect are desired but cannot be performed in the long run due to budget constraints. In this paper, we use a combination of short-term transect-based measurements from a vessel-mounted ADCP and relatively long-term point measurements from a moored ADCP at the bottom to obtain regression coefficients between the transport from the vessel-based observations and the depth-averaged velocity from the bottom-based observations. The method is applied to an Arctic lagoon by using an ADCP mounted on a buoyant platform towed by a small inflatable vessel and another ADCP mounted on a bottom deployed metal frame. The vessel-based measurements were performed continuously for nearly 5 h, which was sufficient to derive a linear regression between the datasets with an R2-value of 0.89. The regression coefficients were in turn applied to the entire time for the moored instrument measurements, which are used in the interpretation of the subtidal transport variations.

Field survey and analysis of water flux and salinity gradients considering the effects of sea ice coverage and rubber dam: a case study of the Liao River Estuary, China

“…The investigation and identification of freshwater input processes are important to understanding how salinity and freshwater transport change in the LRE, a part of which is the estimation of freshwater flux into the estuary. Some researchers developed a convenient way for water volume transport by establishing a correlation between the flow velocity from the bottom-mounted ADCP and an ADCP mounted to the auto-boat in a short period (Li et al, 2018;Weeks et al, 2018;Li and Boswell, 2022). In this study, we carried out a series of field surveys in the LRS, where the width of water surface is about 200 m. The investigation showed that this section of the LRS has complex topographic features and great variation in water depth, as shown in Figure 2.…”

“…The water volume transported into sea was derived from the measured index velocity and tidal level, which has been shown to be a reliable method (Ganju et al, 2012;Weeks et al, 2018;Li and Boswell, 2022) and returned high accuracy in their studies. The results showed that there were apparent spring-neap cycles in the data-based water flux into sea in the LRS.…”

“…In general, quantifying freshwater fluxes along estuarine cross sections can be achieved using a variety of methods. In terms of spatial and temporal measurements, Acoustic Doppler Current Profilers (ADCPs) are advanced tools capable of measuring different water body parameters, and have become standard in measurement methods (Lane et al, 1997;Sakho et al, 2019;Zhu et al, 2021;Li and Boswell, 2022). Straightforward volume calculations can be used to determine water fluxes, where the detailed intertidal bathymetry, tidal current, and accurate tidal water level data based on field surveys are required to obtain a complete coverage of tidally affected areas over tidal timescales (Fukamachi et al, 2010;Li et al, 2018;Shin et al, 2022).…”