Dr Katy Sheen
Lecturer in Physical Geography

Research

Research interests

Sahel Summer Rainfall Variability

The Sahel region of Africa is particularly vulnerable to climate variability. Exhibiting some of the largest rainfall changes worldwide and with a community reliant on agricultural productivity, droughts are major natural disasters for the region. Given that our Earth’s climate is in a state of rapid change, accurate forecasting and a better understanding of the Sahel summer rainy season is of fundamental importance for implementing successful adaptation strategies to ensure the future food security and economic wealth of sub-Saharan Africa.

Working with the inter-annual and decadal climate prediction team at the Met Office, we have utilized state of the art climate models to show that both inter-annual rainfall fluctuations and prolonged drought periods can be successfully predicted across the Sahel. Key to our confidence in the observed statistical skill is the ability to also predict the dominant physical processes that modulate Sahel rainfall. This work has shed new light on the character of Sahel rainfall change on different timescales, particularly in relation to how the different ocean basins impact both the moisture advected into the Sahel and the dynamics that promote ascent of locally sourced moisture.

Seismic Oceanography

Seismic oceanography, in a novel technique that utilises acoustic reflections, as

collected by the hydrocarbon industry, to image temperature and salinity changes within the water column. It is unique in its ability to map out large swathes of ocean structure at unprecedented horizontal resolutions. I believe that seismic

oceanography is likely to have a profound impact on our quantitative understanding of four-dimensional ocean dynamics, key to parameterizing global climate models. Based on my previous work in the field, I am currently engaged in developing an autonomous system for collecting acoustic reflection data from the ocean.

Southern Ocean Dynamics

The Antarctic Circumpolar Current (ACC) that encircles the Antarctic continent, plays a leading role in regulating the Earth’s climate system. Eddies, internal waves and small scale mixing processes are an important component of ACC circulation and dynamics. I’m interested in better quantifying the rates and geographical distribution of the small-scale turbulent mixing in the Southern Ocean, which ultimately control the global oceans transport of heat, carbon and other important climate variables.

Through the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) project, we have made the first dedicated measurements of abyssal turbulent mixing and variability in the Southern Ocean, and how they relate to the larger scale flow. This work has provided unprecedented insights into the mechanisms by which the deep waters of the global oceans are ultimately driven back to the surface, where they can interact with the atmosphere.

Here is a link to a film which we made during my last trip to the Southern Ocean and Antarctica:

A Drop in the Southern Ocean

 

Research projects

OCTONAUT: Ocean impacts of Cryospheric TransformatiON by Antarctic Underwater Turbulence (NERC CASS through the British Antarctic Surbey funded)

The glaciers and ice shelves of the Western Antarctic Peninsula (WAP) are undergoing major changes. Strong glacier retreat rates are observed in many regions, primarily driven by enhanced delivery of warm ocean water at depth. This project will investigate the processes that modulate both the outflow of melt water and the inflow of deep warm along the WAP coastline.

 

ACOUSTIC IMAGING OF SOUTHERN OCEAN FRONTS (SDF funding):

We will be supplementing a geophysical seismic research survey with oceanographic measuements in early 2018 in the Southern Ocean to investigate the physics of Southern Ocean fronts using acoustic and oceanographic data.

 

RAINFALL: Rainfall in Africa INitiative: Forecasting at Longer-Leadtimes (SDF funding):

A succesful field trip to Senegal and Ghana highlighted the need for improved early warning systems for drought and flooding in the Sahel region of Africa. We are currently working with colleagues in these regions to improve forecasting summer rain variability from the previous winter to many years in advance.

 

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