Research

My research focuses on the large-scale ocean circulation, and its impact on and response to climate change.

MOC at 26N: diagram This includes the meridional overturning circulation, large-scale heat flux dynamics, origin and fate of mesoscale energy, deep convection, biophysical interactions, and subpolar ocean dynamics. My research methods are centred on ocean observations, with an aim to capitalise on synergies between datatypes. This means using two or more datatypes (satellite, in situ hydrography, moorings or autonomous platforms) to gain a better understanding of ocean dynamics than would be possible from a single data source. In the past, this has required pushing the limits of observational methods, including using satellite data to unravel space-time aliasing of glider data, and developing a method to extract profiles of vertical water velocities from glider hydrographic data.

Projects

FreshWATERS

Fresh ways of Targeting and Employing Robotic Systems, funded by NERC
with Andras Sobester

Ocean drifters – floating instrument and transmitter packages – are powerful means of mapping surface currents, but their effectiveness and observational efficiency are limited by deployment constraints. We propose a novel, low cost drifter delivery technique, which obviates the need for large vessels: the concept is based on long range, lighter-than-air unmanned delivery platforms. We propose to conduct the preliminary development of the system from the perspective of a candidate application: the observation of freshwater mixing mechanisms in the Labrador Sea.

Link: Freshwaters overview


OPSARS

Oceanography and Polar Science through Agile Robotic Systems, funded by SMMI
with Andras Sobester, Alberto Naveira Garabato, Alex Phillips, Jim Scanlan

We are investigating the feasibility of a disruptive technology for the rapid deployment of oceanographic and polar science instruments through an unmanned system comprising aerial and marine vehicles. This offers a step change in range and speed of deployment over current capabilities of comparable costs. A generic OPSARS system will consist of a long range Unmanned Air Vehicle (UAV), which delivers a light Au- tonomous Underwater Vehicle (AUV) to a pre-determined location, where the AUV is deployed (the UAV performs the deployment in-flight). This enables the rapid long-range deployment of the AUV to remote or inaccessible locations, including cracks in the Arctic ice. The UAV then returns to base, performs an aerial survey or holds on station above the deployment area, acting as a communications relay platform, while the AUV conducts an underwater survey or intervention.


MerMEED

Mechanisms responsible for Mesoscale Eddy Energy Dissipation, funded by NERC
with Alberto Naveira Garabato, Alex Forryan, PDRA: Gwyn Evans

While eddies are present in all ocean basins, with currents inside the eddies sometimes exceeding 1 m/s, they disappear from satellite measurements preferentially at western boundaries. There are several possibilities for why eddies disappear at western boundaries: they may radiate energy away, contribute energy to large scale ocean circulation, or lose energy locally through turbulence and dissipation. Of these candidate terms, previous work has suggested that local dissipation is strong enough to explain a substantial part of the eddy disappearance. Our aim is to determine how and why eddies are losing energy at the western boundaries. These results and our measurements will then be made available to scientists involved in numerical simulations of the ocean. As a longer-term goal, the results of our research may help guide how eddies are represented in ocean models, which is one of the critical areas needing improvement in climate simulations. However, due to the fledgling nature of the science in this field, that eventual goal is still several steps away.

Link: MerMEED overview


DynOPO

Dynamics of the Orkney Passage Outflow, funded by NERC
with Alberto Naveira Garabato, Mike Meredith, Povl Abrahamsen, Keith Nicholls

During the last three decades, the Antarctic Botttom Water (AABW) filling the bulk of the global ocean abyss has exhibited a striking warming and contraction in volume over much of the world ocean, particularly in the Atlantic basin. While the causes of these changes are unknown, available evidence suggests that, in the Atlantic Ocean, the warming and contraction of AABW may be caused by changes in winds over the northern Weddell Sea, where much AABW is produced. This hypothesis asserts that those winds regulate the volume and temperature of the AABW exported northward via the Orkney Passage (a major AABW exit route from the Weddell Sea) by altering the intensity of the turbulent mixing between AABW and overlying warmer waters in the passage.

Link: DynOPO overview


TransAtlantic

Transbasin estimates of the Atlantic MOC, funded through a Leverhulme Trust Research Fellowship
with Felix Landerer, Matthias Lankhorst


Labrador Sea convection, spring bloom, and influence on the AMOC

with Peter Rhines, Charlie Eriksen

The Labrador Sea is one of a handful of sites where deep convection and deep water formation occur. Located in the North Atlantic, between Canada and Greenland, it is considered to be one limb of the downwelling branch of the meridional overturning circulation. Convection is vulnerable to freshwater forcing in the region, at least on paleoclimate timescales, and at present freshwater fluxes from Greenland are increasing. How will the influx of freshwater affect deep convection? or the spring phytoplankton bloom?


RAPID 26N observations of the MOC

Meridional overturning circulation at 26N, funded by NERC/NSF/NOAA
with David Smeed, Bill Johns, Chris Meinen, Gerard McCarthy, Stuart Cunningham, Harry Bryden, Joel Hirschi, Aurelie Duchez

See also Publications