DOI: 10.7280/d1vh54
title: Data from: Fate of internal waves on a shallow shelf

description: Internal waves strongly influence the physical and chemical environment of
 coastal ecosystems worldwide. We report novel observations from a
 distributed temperature sensing (DTS) system that tracked the
 transformation of internal waves from the shelf break to the surf zone
 over a narrow shelf-slope region in the South China Sea. The
 spatially-continuous view of temperature fields provides a perspective of
 physical processes commonly available only in laboratory settings or
 numerical models, including internal wave reflection off a natural slope,
 shoreward transport of dense fluid within trapped cores, and observations
 of internal run-down (near-bed, offshore-directed jets of water preceding
 a breaking internal wave).  Analysis shows that the fate of
 internal waves on this shelf – whether transmitted into shallow waters or
 reflected back offshore – is mediated by local water column density
 structure and background currents set by the previous shoaling internal
 waves, highlighting the importance of wave-wave interactions in nearshore
 internal wave dynamics.
description: In this paper we present
 observations of internal waves shoaling on the shallow shelf-slope of
 Dongsha Atoll, a coral reef ecosystem in the South China Sea (Fig. 1a-c).
 Dongsha is directly in the path of some of the world’s largest internal
 solitary waves [<i>Alford</i>, 2015; <i>Guo and
 Chen</i>, 2014; <i>Hsu</i>, 2000; <i>Lien et
 al.</i>, 2005].  These waves evolve from steepened internal tides in
 Luzon Strait and propagate westward across the deep basin of the northern
 South China Sea with wavelengths of <i>O</i>(3-10 km), often
 developing into wave trains [<i>Alford</i>, 2015]. As the
 solitary waves shoal up onto the continental slope they steepen even
 further with amplitudes as large as 150-200 m and wavelengths of only a
 few hundred meters.  At this point they can become susceptible to both
 convective and shear instabilities which cause them to break and drive
 huge vertical overturns, energetic mixing, and energy dissipation
 [<i>Chang et al.</i>, 2006; <i>St. Laurent</i>,
 2008].   The shallow (&lt; 25 m) slope of Dongsha
 Atoll is an internal swash zone, where the end-of-life of these large
 internal waves takes the form of bottom-propagating solibores and
 boluses.  They spend their remaining energy bringing deep water up to the
 surface where it has significant effects on the reef heat and nutrient
 budgets [<i>Reid et al.</i>, 2019].  From 1-17 June 2014, we
 deployed Distributed Temperature Sensing (DTS) instrumentation to capture
 spatially-continuous observations of near-bed temperature on the fore reef
 slope of Dongsha Atoll to evaluate the path (or “fate”) of internal waves
 shoaling onto the shelf and moorings to measure the vertical structure of
 velocity and density stratification. A semi-idealized numerical simulation
 is used to help interpret the novel perspective provided by the DTS
 observations.   Here a
 four-channel DTS system (Sensornet Oryx) was used to capture a continuous
 view of near-bed temperature in a cross-shelf profile on the east fore
 reef of Dongsha Atoll.  Four kilometers of Kaiphone 0.6 cm-diameter fiber
 optic cable was deployed in a cross-shelf orientation (285°, aligned
 approximately parallel to the propagation direction of the offshore
 internal wave field [<i>Ramp</i>, 2010], beginning at the back
 of the reef flat (~2 m depth) and terminating offshore at 50-m depth on
 the fore reef (Fig. 1c).   In this study we focus on the offshore-most ~1
 km of the FO cable - from the reef crest down the fore reef slope – the
 reader is referred to <i>Reid et al.</i> [2019] for further
 information about the shallow reef DTS results.  The FO cable followed the
 bottom contours of the bed, except in areas with extreme changes in
 topography (such as a coral groove) where the cable was raised above the
 bed by up to 0.5 m.  The DTS collected temperature traces along the cable
 every minute with 2-m spatial resolution from 2-12 June 2014.  A tropical
 storm in the vicinity of Dongsha Atoll reduced solar power and prevented
 further DTS measurements after 12 June, however, measurements from
 vertical arrays (Section 2.3) continued until 17 June 2014.
description: Notes on E1 Mooring and DTS Calibration and Validation loggers
 located in data folders