The oceans play a hugely important role in the global carbon cycle and in energy transport mechanisms that influence world climate. Monitoring oceans is difficult due to the vast areas involved, the harsh environmental conditions and the rapid temporal variability of marine biogeochemical systems. Optical sensors can provide information about biological and mineral particles and dissolved substances. The technology is particularly suitable as optical sensors can be deployed on a variety of platforms, from satellites and aircraft to in situ moorings and underwater vehicles. David’s research is currently focused on improving the quality of products obtained from ocean colour remote sensing signals and in situ optical measurements of absorption, scattering and fluorescence. He is also interested in development of new platforms for optical instruments in oceanography such as micro-satellites for Earth observation and in situ profiling moorings. The research combines significant time spent at sea making measurements, numerical simulation of underwater and water leaving light fields and statistical data analysis. Most of the work is concentrated on optically complex shelf seas (e.g. Bristol Channel, Irish Sea, Mediterranean) where the influence of terrestrial and anthropogenic sources are strongest, though more recently he has started to develop interests in optical complexity in more open ocean areas that are subject to episodic inputs of wind-borne particulates. A key element of David’s NERC Fellowships has been the development of several very successful collaborations with partners in UK and international institutions.
Our group is interested in problems of radiance transfer in seawater, light utilisation by phytoplankton, optical monitoring of ecological processes, and remote sensing in the marine environment. These problems all involve the application of physical principles in an interdisciplinary context. Activities range from in situ measurement of optical properties at sea from ships and other platforms, through radiative transfer simulations of underwater and water leaving light fields, to development of new algorithms for interpretation of ocean colour remote sensing data from satellite-borne sensors.
- Invited Talk
- NEODAAS (External organisation)
- NERC Field Spectroscopy Facility (External organisation)
- Invited Talk
- Invited Talk
- Optics Express (Journal)
- Associate Editor
more professional activities
- Sustainable harvesting of a patchy resource: aggregation mechanisms and implications for stock size estimates (SEA PATCHES)
- McKee, David (Principal Investigator)
- Period 01-Apr-2017 - 31-Mar-2021
- Arctic PRoductivity in the seasonal Ice ZonE (Arctic PriZE)
- Banas, Neil (Principal Investigator) McKee, David (Co-investigator)
- "Arctic PRIZE will address the core objective of the Changing Arctic Ocean Program by seeking to understand and predict how change in sea ice and ocean properties will affect the large-scale ecosystem structure of the Arctic Ocean. We will investigate the seasonally and spatially varying relationship between sea ice, water column structure, light, nutrients and productivity and the roles they play in structuring energy transfer to pelagic zooplankton and benthic megafauna. We focus on the seasonal ice zone (SIZ) of the Barents Sea - a highly productive region that is undergoing considerable change in its sea ice distribution - and target the critically important but under-sampled seasonal transition from winter into the post-bloom summer period. Of critical importance is the need to develop the predictive tools necessary to assess how the Arctic ecosystems will respond to a reducing sea ice cover. This will be achieved through a combined experimental/modelling programme. The project is embedded within international Arctic networks based in Norway and Canada and coordinated with ongoing US projects in the Pacific Arctic. Through these international research networks our proposal will have a legacy of cooperation far beyond the lifetime of the funding. The project comprises five integrated work packages.
WP1 Physical Parameters: We will measure properties of the water column (temperature, salinity, turbulent fluxes, light, fluorometry) in both open water and under sea ice by deploying animal-borne tags on seals which preferentially inhabit the marginal ice zone (MIZ). We will use ocean gliders to patrol the water around the MIZ and track it as the ice retreats northwards in summer. Measurements of underwater light fields will support development of improved regional remote sensing algorithms to extend the spatial and temporal context of the proposal beyond the immediate deployment period.
WP2 Nutrient Dynamics: We will undertake an extensive program of measuring inorganic and organic nutrients, their concentrations, isotopic signatures and vertical fluxes to understand the role of vertical mixing and advection (WP1) in regulating nutrient supply to PP in the surface ocean.
WP3 Phytoplankton Production: We will investigate nutrient supply (WP2) and light availability (WP1) linked to sea ice affect the magnitude, timing, and composition of phytoplankton production, and the role of seasonal physiological plasticity. Through new numerical parameterisations - cross-tuned and validated using a rich array of observations - we will develop predictive skill related to biological production and its fate; resolve longstanding questions about the competing effects of increased light and wind mixing associated with sea ice loss; and therefore contribute to the international effort to project the functioning of Pan-Arctic ecosystems.
WP4 Zooplankton Behaviour: Zooplankton undergo vertical migrations to graze on PP at the surface. We will use acoustic instruments on moorings and AUVs, with nets and video profiles to measure the composition and behaviours of pelagic organisms in relation in light and mixing (WP1) and phytoplankton production (WP3) over the seasonal cycle of sea ice cover. The behaviours identified will be used to improve models that capture the life-history and behavioural traits of Arctic zooplankton. These models can then be used to investigate how feeding strategies of key Arctic zooplankton species may be modified during an era of reducing sea ice cover.
WP5 Benthic Community: We will use an AUV equipped with camera system to acquire imagery of the large seabed-dwelling organisms to investigate how changes in sea ice duration (WP1), timing of PP (WP3) and bentho-pelagic coupling (WP4) can modify the spatial variation in benthic community composition. We will also conduct time series-studies in an Arctic fjord using a photolander system to record the seasonally varying community response to pulses of organic matter."
- Period 01-May-2017 - 30-Apr-2021
- Cost-effective medical hyperspectral imaging
- Marshall, Stephen (Principal Investigator) McConnell, Gail (Co-investigator) McKee, David (Co-investigator) Ren, Jinchang (Co-investigator)
- Period 01-Jul-2016 - 30-Jun-2018
- ORANGUTRAN - ORbital ANGUlar momentum TRANsmissometer with zero collection angle error
- McKee, David (Principal Investigator) Griffin, Paul (Co-investigator) Yao, Alison (Co-investigator)
- "Light passing through natural water systems experiences both absorption and scattering leading to important effects such as heating of the water, growth of plants through photosynthesis and generation of reflectance signals for remote sensing systems. One of the most common measures of the optical properties of a water body is the beam attenuation coefficient which is the sum of absorption and scattering. This is usually measured by recording the intensity of a beam of light after it has passed through a known length of water and comparing the signal with that obtained either in air or, more usually, in ultrapure water. It is usually assumed that any photons either absorbed or scattered do not make it to the detector and so the remaining signal is due entirely to directly transmitted photons. However, in reality, light is scattered in water in such a way that standard transmissometers accidentally collect a large and quite variable amount of forward scattered light. This means that the signal they generate has a large error that is actually a feature of the instrument design, and sensors with different optical layouts will provide substantially different values. It has long been thought that this was an inevitable feature of the measurement and most users simply ignore the problem. Indeed, current NASA measurement protocols for this parameter explicitly leave it to the end user of data to work out how to deal with this problem. This is an intolerable position for which we have recently found a new solution.
We are planning to build a new device to measure beam attenuation that exploits a recently developed understanding of a quantum property of photons called orbital angular momentum, OAM. We can control this quantum state of light and generate a beam of light with a defined OAM state. When such a beam of light experiences a scattering event, the OAM state changes by a defined, quantum amount that we can easily identify. We can use this change of quantum state to effectively label scattered photons and discriminate them from directly transmitted photons. This means we can measure the number of photons that make it across a volume of water without being absorbed or scattered, without being affected by the scattering collection error that causes problems for current instruments. Our device will then be significantly more accurate than what is currently available and will help researchers and other end-users make significantly better and consistent measurements of what is an extremely important optical property of natural water systems."
- Period 30-Jun-2016 - 29-Jun-2017
- NERC Doctoral Training Grant (NE/I528685/1) | Mitchell, Catherine
- McKee, David (Co-investigator) Mitchell, Catherine (Research Co-investigator)
- Period 01-Oct-2011 - 22-Apr-2015
- Strathclyde-2013-DTG Funding 1 Studentship | Connor, Derek
- McKee, David (Principal Investigator) McConnell, Gail (Co-investigator) Connor, Derek (Research Co-investigator)
- Period 01-Oct-2013 - 01-Apr-2017
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