Chad Lembke

Underwater mass spectrometers for in situ chemical analysis of the hydrosphere

Underwater mass spectrometry systems can be used for direct in situ detection of volatile organic compounds and dissolved gases in oceans, lakes, rivers and waste-water streams. In this work we describe the design and operation of (1) a linear quadrupole mass filter and (2) a quadrupole ion trap mass spectrometer interfaced, in each case, with a membrane introduction/fluid control system and packaged for underwater operation. These mass spectrometry systems can operate autonomously, or under user control via a wireless rf link. Detection limits for each system were determined in the laboratory using pure solutions. The quadrupole mass filter system provides detection limits in the 1–5 ppb range with an upper mass limit of 100 amu. Its power requirement is approximately 95 Watts. The ion trap system has detection limits well below 1 ppb, an upper mass limit of 650 amu and MS/MS capability. Its power consumption is on the order of 150 Watts. The present membrane limits analysis to non-polar compounds (<300 amu) with analysis cycles of 5–15 minutes. Deployments of both types of instruments are described, along with a discussion of the challenges associated with in-water mass spectrometry and descriptions of alternative in-water mass spectrometer configurations.

Development of an underwater mass-spectrometry system for in situ chemical analysis

Progress in the design, construction and packaging of small portable mass spectrometers for operation on autonomous underwater vehicles (AUVs) is described. Our first deployable version consists of a membrane introduction interface coupled with a linear quadrupole mass filter for in situ detection and quantification of dissolved gases and volatile organic compounds. We present laboratory results which demonstrate that sub-parts-per-billion detection limits have been achieved for toluene. The mass-spectrometer system is compatible with AUV constraints and operates on 24 V dc, consuming of the order of 100 W of power. Technical challenges of performing underwater mass spectrometry are addressed, in particular sample introduction from the water column and the maintenance of a vacuum system. Initial operation will be in shallow water of 30 m depth or less. Alternative versions of interfaces and mass spectrometers are also discussed. We anticipate that providing the capability of performing in situ underwater mass-spectrometric analysis will have a significant impact in the areas of marine science and environmental monitoring.

Tracking Ships from Fast Moving Camera through Image Registration

This paper presents an algorithm that detects and tracks marine vessels in video taken by a nonstationary camera installed on an untethered buoy. The video is characterized by large inter-frame motion of the camera, cluttered background, and presence of compression artifacts. Our approach performs segmentation of ships in individual frames processed with a color-gradient filter. The threshold selection is based on the histogram of the search region. Tracking of ships in a sequence is enabled by registering the horizon images in one coordinate system and by using a multihypothesis framework. Registration step uses an area-based technique to correlate a processed strip of the image over the found horizon line. The results of evaluation of detection, localization, and tracking of the ships show significant increase in performance in comparison to the previously used technique.

Design and initial results of a bottom stationing ocean profiler

The benefits of untethered or drifting buoys and platforms have been well documented over the past decade. Study of physical, chemical and biological processes in the ocean can often be optimized using systems that profile and/or drift. However, it is at times useful to station a sensing system so that measurements are made only after or during specific conditions, e.g. a storm, an algae bloom, or underwater geologic event. A new autonomous platform has been developed that can provide the benefits of an untethered drifter while also providing the benefits of a stationary buoy. The Bottom Stationing Ocean Profiler (BSOP) is an instrument platform that stations itself on the sea floor and ascends and descends autonomously to gather water column profile data. While at the surface the BSOP transmits acquired data via the ORBCOMM satellite system to provide researchers with a near real-time observation of the study area. The BSOP unit is designed to remain at sea for extended periods up to several months. It uses an oil-based buoyancy control system to ascend and descend at speeds up to 0.5 meters per second. The unit is low cost, easy to deploy and recover using only light duty gear and can support a wide variety of sensors. Command scripts are downloadable while the unit is in communication with a satellite ground station; this permits reprogramming of mission parameters if needed. The unit has an integral global positioning system receiver to accurately identify surface position. This is important to the scientific mission but is also used for recovery operations. BSOP design and early results are presented.

Autonomous buoy platform for low-cost visual maritime surveillance: design and initial deployment

We report on the design and evaluation of the initial results of operation of a prototype of an advanced system for maritime security. The system is autonomous and is designed to remain in the ocean for extended periods up to two months. It is based on the Bottom Stationing Ocean Profiler (BSOP), an un-tethered, autonomous platform that stations itself on the sea floor and ascends to the surface at specific time intervals or, potentially, when triggered by certain events such as recognizable acoustic signals, collected and analyzed on board. The surface operations of the system include optical data acquisition, image data analysis, communication with the ground station, and retrieval based functionality. The system is designed to take video and imagery of the surrounding ocean surface and analyze it for the presence of ships, thus, potentially enabling automatic detection and tracking of marine vehicles as they transit in the vicinity of the platform. The system transmits the data to the ground control via bi-directional RF satellite link and can have its mission parameters reprogrammed during the deployment. The described unit is low cost, easy to deploy and recover, and does not reveal itself to the potential targets. The paper describes the system hardware, architecture, algorithms for visual ship detection and tracking.

Emerging technology monitors ice-sea interface at outlet glaciers

Recent melting in Greenland and Antarctica has led to concerns about the long-term stability of these ice sheets and their potential contributions to future sea level rise. Marine-terminating outlet glaciers play a key role in the dynamics of these ice sheets; recent mass losses are likely related to increased influx of warmer water to the base of outlet glaciers, as evidenced by the fact that changes in ocean currents, calving front retreats, glacial thinning, mass redistribution based on satellite gravity data, and accelerating coastal uplift are roughly concurrent [e.g., Holland et al., 2008; Wouters et al., 2008; Jiang et al., 2010; Straneo et al., 2012; Bevis et al., 2012]. However, collecting quantitative measurements within the dynamic environment of marine outlet glaciers is challenging. Oceanographic measurements are limited in iceberg-laden fjords. Measuring ice flow speeds near the calving front is similarly challenging; satellite methods lack temporal resolution (satellite revisit times are several days or longer), while GPS gives limited spatial resolution, a problem for assessing changes near the highly variable calving front.

Observations of inertial currents in a lagoon in southeastern Iceland using terrestrial radar interferometry and automated iceberg tracking

Warming ocean currents are considered to be a contributing factor to the retreat of marine-terminating glaciers worldwide, but direct observations near the ice-ocean interface are challenging. We use radar intensity imagery and an iceberg tracking algorithm to produce half-hourly current maps within an imaged portion of Jokulsarlon, a proglacial lagoon in southeastern Iceland. Over our 43.5-h observation period, the lagoon has clockwise circulation with current speeds of order 3-8cm/s and occasional strong glacier outflows of up to ~15cm/s. The currents driven by the glacial outflows appear to be dominantly inertial. HighlightsWe track iceberg motion in a glacial lagoon using terrestrial radar intensity images.We use a PTV approach to track the icebergs.We interpolate the currents using radial basis functions.Subglacial outflows contribute to inertial circulation in the lagoon.

Vertical migration of Karenia brevis in the northeastern Gulf of Mexico observed from glider measurements

The toxic marine dinoflagellate, Karenia brevis (the species responsible for most of red tides or harmful algal blooms in the Gulf of Mexico), is known to be able to swim vertically to adapt to the light and nutrient environments, nearly all such observations have been made through controlled experiments using cultures. Here, using continuous 3-dimensional measurements by an ocean glider across a K. brevis bloom in the northeastern Gulf of Mexico between 1 and 8 August 2014, we show the vertical migration behavior of K. brevis. Within the bloom where K. brevis concentration is between 100,000 and 1,000,000cellsL-1, the stratified water shows a two-layer system with the depth of pycnocline ranging between 14-20m and salinity and temperature in the surface layer being <34.8 and >28°C, respectively. The bottom layer shows the salinity of >36 and temperature of <26°C. The low salinity is apparently due to coastal runoff, as the top layer also shows high amount of colored dissolved organic matter (CDOM). Within the top layer, chlorophyll-a fluorescence shows clear diel changes in the vertical structure, an indication of K. brevis vertical migration at a mean speed of 0.5-1mh-1. The upward migration appears to start at sunrise at a depth of 8-10m, while the downward migration appears to start at sunset (or when surface light approaches 0) at a depth of ∼2m. These vertical migrations are believed to be a result of the need of K. brevis cells for light and nutrients in a stable, stratified, and CDOM-rich environment.

A national glider network for sustained observation of the coastal ocean

A national glider network is essential to provide baseline ocean observations to connect the coastal and global ocean, and to address such issues as natural climate variability, ecosystem health, and water quality. The development of gliders is briefly reviewed. Requirements for a national network are presented, and the capabilities of gliders are shown to be suited for the task. The needs of a data management system tuned to gliders are outlined. A workshop to outline a strategy towards creating this network was held in August 2012, with a planning document to follow.

Temporal and spatial mapping of red grouper Epinephelus morio sound production.

The goals of this project were to determine the daily, seasonal and spatial patterns of red grouper Epinephelus morio sound production on the West Florida Shelf (WFS) using passive acoustics. An 11 month time series of acoustic data from fixed recorders deployed at a known E. morio aggregation site showed that E. morio produce sounds throughout the day and during all months of the year. Increased calling (number of files containing E. morio sound) was correlated to sunrise and sunset, and peaked in late summer (July and August) and early winter (November and December). Due to the ubiquitous production of sound, large-scale spatial mapping across the WFS of E. morio sound production was feasible using recordings from shorter duration-fixed location recorders and autonomous underwater vehicles (AUVs). Epinephelus morio were primarily recorded in waters 15-93 m deep, with increased sound production detected in hard bottom areas and within the Steamboat Lumps Marine Protected Area (Steamboat Lumps). AUV tracks through Steamboat Lumps, an offshore marine reserve where E. morio hole excavations have been previously mapped, showed that hydrophone-integrated AUVs could accurately map the location of soniferous fish over spatial scales of <1 km. The results show that passive acoustics is an effective, non-invasive tool to map the distribution of this species over large spatial scales.