Combining continuous spatial and temporal scales for SGD investigations using UAV-based thermal infrared measurements

Mallast, Ulf; Siebert, Christian

doi:10.5194/hess-23-1375-2019

Cited by 17 publications

(12 citation statements)

References 46 publications

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“…3 for an example). As the bubbles in the turbulent wake reflect the sound more efficiently than water, they induce an elevated echo amplitude in the turbulent wake region (NDRC, 1946;Marmorino and Trump, 1996;Trevorrow et al, 1994;Weber et al, 2005;Ermakov and Kapustin, 2010;Francisco et al, 2017). Generally, the wake signal could be clearly distinguished from bubbles induced by waves or signal noise from fish or zooplankton.…”

Section: Compiling the Adcp Wake Datasetmentioning

confidence: 99%

In situ observations of turbulent ship wakes and their spatiotemporal extent

et al. 2021

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Abstract. In areas of intensive ship traffic, ships pass every 10 min. Considering the amount of ship traffic and the predicted increase in global maritime trade, there is a need to consider all types of impacts shipping has on the marine environment. While the awareness about, and efforts to reduce, chemical pollution from ships is increasing, less is known about physical disturbances, and ship-induced turbulence has so far been completely neglected. To address the potential importance of ship-induced turbulence on, e.g., gas exchange, dispersion of pollutants, and biogeochemical processes, a characterisation of the temporal and spatial scales of the turbulent wake is needed. Currently, field measurements of turbulent wakes of real-size ships are lacking. This study addresses that gap by using two different methodological approaches: in situ and ex situ observations. For the in situ observations, a bottom-mounted acoustic Doppler current profiler (ADCP) was placed at 32 m depth below the shipping lane outside Gothenburg harbour. Both the acoustic backscatter from the air bubbles in the wake and the dissipation rate of turbulent kinetic energy were used to quantify the turbulent wake depth, intensity, and temporal longevity for 38 ship passages of differently sized ships. The results from the ADCP measurements show median wake depths of 13 m and several occasions of wakes reaching depths > 18 m, which is in the same depth range as the seasonal thermocline in the Baltic Sea. The temporal longevity of the observable part of the wakes had a median of around 10 min and several passages of > 20 min. In the ex situ approach, sea surface temperature was used as a proxy for the water mass affected by the turbulent wake (thermal wake), as lowered temperature in the ship wake indicates vertical mixing in a thermally stratified water column. Satellite images of the thermal infrared sensor (TIRS) onboard Landsat-8 were used to measure thermal wake width and length, in the highly frequented and thus major shipping lane north of Bornholm, Baltic Sea. Automatic information system (AIS) records from both the investigated areas were used to identify the ships inducing the wakes. The satellite analysis showed a median thermal wake length of 13.7 km (n=144), and the longest wake extended over 60 km, which would correspond to a temporal longevity of 1 h 42 min (for a ship speed of 20 kn). The median thermal wake width was 157.5 m. The measurements of the spatial and temporal scales are in line with previous studies, but the maximum turbulent wake depth (30.5 m) is deeper than previously reported. The results from this study, combined with the knowledge of regional high traffic densities, show that ship-induced turbulence occurs at temporal and spatial scales large enough to imply that this process should be considered when estimating environmental impacts from shipping in areas with intense ship traffic.

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Section: Compiling the Adcp Wake Datasetmentioning

confidence: 99%

In situ observations of turbulent ship wakes and their spatiotemporal extent

et al. 2021

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“…More recently, Mallast and Siebert [44] investigated variations in thermal radiatio induced by focused and diffuse SGD in a sedimentary fan of the Dead Sea. The autho used a hoovering UAS equipped with a long-wave TIR camera and a radiometry modu This work evidenced that UASs offer better results in the study of SGD dynamics in small, localized target areas (0.01-1 km 2 ) than manned aircrafts, which are more adequate for regional characterizations.…”

Section: Submarine Groundwater Discharge (Sgd) Mappingmentioning

confidence: 99%

“…More recently, Mallast and Siebert [44] investigated variations in thermal radiation induced by focused and diffuse SGD in a sedimentary fan of the Dead Sea. The authors used a hoovering UAS equipped with a long-wave TIR camera and a radiometry module and assumed that thermally stable areas indicated focused SGD whereas highly variable areas indicated diffuse SGD.…”

Section: Submarine Groundwater Discharge (Sgd) Mappingmentioning

confidence: 99%

Applications of Unmanned Aerial Systems (UASs) in Hydrology: A Review

et al. 2021

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In less than two decades, UASs (unmanned aerial systems) have revolutionized the field of hydrology, bridging the gap between traditional satellite observations and ground-based measurements and allowing the limitations of manned aircraft to be overcome. With unparalleled spatial and temporal resolutions and product-tailoring possibilities, UAS are contributing to the acquisition of large volumes of data on water bodies, submerged parameters and their interactions in different hydrological contexts and in inaccessible or hazardous locations. This paper provides a comprehensive review of 122 works on the applications of UASs in surface water and groundwater research with a purpose-oriented approach. Concretely, the review addresses: (i) the current applications of UAS in surface and groundwater studies, (ii) the type of platforms and sensors mainly used in these tasks, (iii) types of products generated from UAS-borne data, (iv) the associated advantages and limitations, and (v) knowledge gaps and future prospects of UASs application in hydrology. The first aim of this review is to serve as a reference or introductory document for all researchers and water managers who are interested in embracing this novel technology. The second aim is to unify in a single document all the possibilities, potential approaches and results obtained by different authors through the implementation of UASs.

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“…Second, since the temporal variability of the STE-associated processes is high, an interesting approach would be to have a TIR remote sensing approach that enables a multi-temporal observation possibility. The recent advance of UAVs do provide such a possibility, as shown in Mallast and Siebert (2019), but cannot cover a regional scale simultaneously. The revisiting times will be reduced for Landsat with the launch of Landsat-9 in spring 2021 and the Indian-French THRISHNA mission, whose launch is planned for 2024 (Lagouarde et al, 2018).…”

Section: Remote Sensingmentioning

confidence: 99%

A State-Of-The-Art Perspective on the Characterization of Subterranean Estuaries at the Regional Scale

et al. 2021

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Subterranean estuaries the, subsurface mixing zones of terrestrial groundwater and seawater, substantially influence solute fluxes to the oceans. Solutes brought by groundwater from land and solutes brought from the sea can undergo biogeochemical reactions. These are often mediated by microbes and controlled by reactions with coastal sediments, and determine the composition of fluids discharging from STEs (i.e., submarine groundwater discharge), which may have consequences showing in coastal ecosystems. While at the local scale (meters), processes have been intensively studied, the impact of subterranean estuary processes on solute fluxes to the coastal ocean remains poorly constrained at the regional scale (kilometers). In the present communication, we review the processes that occur in STEs, focusing mainly on fluid flow and biogeochemical transformations of nitrogen, phosphorus, carbon, sulfur and trace metals. We highlight the spatio-temporal dynamics and measurable manifestations of those processes. The objective of this contribution is to provide a perspective on how tracer studies, geophysical methods, remote sensing and hydrogeological modeling could exploit such manifestations to estimate the regional-scale impact of processes in STEs on solute fluxes to the coastal ocean.

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Combining continuous spatial and temporal scales for SGD investigations using UAV-based thermal infrared measurements

Abstract: Submarine groundwater discharge (SGD) isPublished by Copernicus Publications on behalf of the European Geosciences Union.

Cited by 17 publications

References 46 publications

In situ observations of turbulent ship wakes and their spatiotemporal extent

In situ observations of turbulent ship wakes and their spatiotemporal extent

Applications of Unmanned Aerial Systems (UASs) in Hydrology: A Review

A State-Of-The-Art Perspective on the Characterization of Subterranean Estuaries at the Regional Scale

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