Fully funded PhD studentships

Uncertainty in flood inundation modelling

This PhD forms part of the recently awarded £2M to look at the impact of uncertainty in environmental models on decision making. This is part of the Natural Environment Research Council ‘Probability, Uncertainty and Risk in the Environment’ programme and is led from Bristol by Professor Thorsten Wagener. As part of this programme this PhD looks at uncertainty in flood inundation models, which are used as the basis of multi-million pound decisions taken routinely by the UK Government and the insurance industry. Typically the use of these models makes no allowance for uncertainty, yet it is clear that significant uncertainty arises from the data and parameters used to build such models and even from the choice of model structure itself.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Professor Paul Bates

Modelling global zooplankton diversity and response to climate change

Models are essential to link our multidisciplinary understanding of ocean processes with observations and to make projections of the potential consequences of global change on marine ecosystems and carbon cycling. Considerable progress has been made in representing the physics of ocean circulation and more recently in the ecology of phytoplankton (see Figure), but the representation of zooplankton such as foraminifera, which play a key role in transforming the fluxes of carbon and nutrients fixed by phytoplankton as well as in producing calcium carbonate (Schmidt et al., 2006), has to date been limited.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Dr Fanny Monteiro

How do rainstorms shape dryland river basins?

Dryland catchments are fascinating yet poorly studied fluvial systems which are highly sensitive to climatic characteristics. They contrast markedly in behaviour and evolution from humid fluvial systems due to differences in surface characteristics and in the nature of the climate, which give rise to distinct hydrological and erosional regimes. Currently there is no understanding of how dryland basins are shaped in response to changes in the relative balance between hillslope and channel processes, especially associated with regional climate change that alters the magnitude and frequency of extreme events. As dryland environments occupy 41% of the Earth’s surface and are home to a third of the world’s population, understanding the response of dryland river basins to climatic shifts is important because they may impact the availability of water resources, risks of extreme flooding, rates of reservoir siltation and the fate and transport of contaminants.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Dr Katerina Michaelides

Microbial biogeography and metabolic diversity in the cryosphere

Recent studies of microbes in polar regions have revealed higher diversities of viruses, bacteria, and protists, in marked contrast to the well documented pattern of decreasing biological diversity in macrofauna and flora with increasing latitudes. This implies that certain combinations of physical and geochemical factors enable microbial diversity and activity in glaciers to remain high despite the extreme environmental conditions these habitats provide, e.g. extreme cold, desiccation, and oligotrophy. Glaciers cover ~10% of the Earth’s land area at present, and the biodiversity and thus, metabolic potential of these extreme habitats may be significant on a global scale. There are just a few studies of microbial diversity in glaciers (both surface and subglacial habitats), largely based on culture-dependent, microscopic observations and/or PCR-based approaches. Hence, the full diversity of glacier ecosystems remains largely unquantified. In addition, there have been few integrated studies which link microbial diversity to ecosystem function and the biogeochemical cycling of key elements (C, N, Fe), the latter of which may have impacts at regional and global scales.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Dr Alexandre Anesio

Evolution of cyanobacteria in the crysophere

Cyanobacteria are major primary producers in the cryosphere. Microbemineral aggregates made by filamentous cyanobacteria help engineer their habitat, thereby making them key ecological components in glacial habitats. Environmental studies of cyanobacteria from glacial ecosystems have shown a diverse cyanobacterial microbial community. However, there is no comprehensive evolutionary information of cold adapted cyanobacteria. A robust evolutionary study of cyanobacteria from cold environments will give a framework within which to study past climatic events. This PhD project aims to isolate and sequence genomes of cyanobacteria from cryolake and glacial samples from a diverse range of habitats in Canada, Greenland and Antarctica. Genomic DNA samples will be sequenced using Next Generation Sequencing and the data will be added to current up-todate genomic data sets, currently containing 69 cyanobacteria taxa with 139 phylogenetic informative genes. Phylogenetic and molecular clock analyses will give new insights into how many times cyanobacteria have adapted to cold environments. The timing of these evolutionary events will be estimated and linked to past climatic events. A significant part of the biosphere is permanently cold with temperatures lower than 5°C and we predict that cold habitats are hot spots of cyanobacteria evolution.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact:Dr Alexandre Anesio

Exploring the Subglacial Biogeochemical Reactor and its Role in Global Biogeochemical Cycles and Climate

An increasing number of observations highlight the role of subglacial sedimentary environments as highly active biogeochemical reactors. These environments may deliver a globally significant flux of bioavailable nutrients, such as dissolved iron (Fe), silica (Si) or dissolved phosphorous (DIP) to the adjacent polar ocean. The lateral fluxes out of this intriguing, but still comparably unexplored environments exert not only an important influence on the biogeochemical dynamics of the adjacent polar ocean, but may also play a significant, yet unconsidered, role for global biogeochemical cycles and climate. Despite the widely accepted global importance of these fluxes, a detailed quantitative understanding of the complex interplay of subglacial biogeochemical processes that controls their exact composition and magnitude is essentially missing. However, an assessment of their impact on polar ocean dynamics and their significance for the climate system inevitably requires such an understanding.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Professor Martyn Tranter

Ice Sheets as vast methanogenic wetlands – an experimental and numerical modelling study into methane production under ice

Once thought to be devoid of life, the basal regions of glaciers and ice sheets are now known to be viable habitats for microorganisms. The activity of these organisms within the deep sub-surface designates ice sheets as important regulators of Earth’s global biogeochemical cycles (Wadham, et al., 2010). For example, microbial activity at the ice sheet bed produces runoff that is rich in labile dissolved organic carbon that may be important in sustaining downstream ecosystem productivity (Hood, et al., 2009), and the activity of anaerobic micro-organisms produces methane gas from organic carbon in sediments (Boyd, et al., 2010, Wadham, et al., 2012, Wadham, et al., 2008). While these ideas are becoming well established, the detailed pathways of microbial metabolism and biogeochemical feedbacks within contrasting glacial systems are poorly understood. Many large glacial systems sequester organic carbon from surrounding ecosystems (e.g. marine sediments, lake sediments, soils) during periods of glacial advance. This overridden organic carbon can subsequently be degraded by subglacial micro-organisms to greenhouse gases, CO2 and CH4. The resultant CH4 gas may be stored during glaciation as methane hydrate, and released rapidly during deglaciation, acting as a positive feedback on climate warming. There is considerable interest at present in the fate of organic carbon beneath ice sheets, and the magnitude of methane production during periods of glaciation. The field, experimental and numerical modelling work to underpin these assertions, however, is in its infancy.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Prof Jemma Wadham

Rice Cake or Cheeseburger? Quantifying Environmental Controls on Organic Matter Reactivity in Marine Sediments

The degradation of organic matter in marine sediments is a key process in the global carbon cycle. It controls, among others, the size of the methane gas hydrate inventory, the formation of petroleum source rocks, the flux of organic carbon to the deep biosphere, the accumulation of oxygen in the atmosphere and the long-term burial of carbon in marine sediments. In short, it is perhaps the most important control on the Earth’s climate and the chemical state of its atmosphere, oceans and soil. Yet, little is known about the set of interplaying environmental factors that control the susceptibility of organic matter degradation to microbial decay in marine sediments.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Dr Sandra Arndt

Modelling Mediterranean Oceans.

The occurrence of organic-rich layers in sediment cores indicates that the Earth System can experience significant perturbations to the carbon-cycle. These layers are of major importance for hydrocarbon formation yet the precise mechanisms that control their formation remain elusive. In the Mediterranean, numerous organic rich layers (sapropels) formed during the Pleistocene, the last one between 9.5 and 5.5 thousand years ago. Although extensive research based on proxy records has demonstrated that the formation of these layers reflects changes in the organic flux to the sea floor and/or its preservation, the relative importance of these controls remains controversial.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Prof Paul Valdes

Palaeoclimate Model Intercomparison Project

Records of palaeoclimate change have been important in identifying key processes and mechanisms of change, such as the links between climate and carbon cycle (from the ice cores) or rapid changes in ocean circulation (from ocean cores). However there are no true palaeoclimate analogues for projected future climates but changes in the past could be used to test how realistic the models are to various climate forcings. This is the rationale behind the Palaeoclimate Model Intercomparison project (PMIP). The aim is to run the latest stateof- the-art IPCC-class climate models for a number of different past time periods and to compare the results across the different models, and to data.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Prof Paul Valdes

Feedbacks between land-use and Atlantic decadal variability: impacts for decadal predictions for Europe

Anthropogenic climate change is predicted to continue over the coming century and beyond. On shorter timescales natural climate variability has a considerable influence on the ability to predict climate change. This variability on inter-annual to multidecadal scales can overprint anthropogenic changes and can also be affected by them. The need to improve these timescales of climate prediction has been highlighted in the past few years (Haines et al., 2009) in its importance for government and business planning. The North Atlantic is one region that displays coupled ocean-atmosphere variability, such as the North Atlantic Oscillation (NAO; Hurrell and van Loon, 1997). Such variability has an impact on European climate (Sutton and Hodson, 2005) and climate change predictions using climate models. It also influences more idealised climate sensitivity experiments (e.g. Singarayer et al., 2009). Understanding this decadal variability, its imprint on regional climate, and its predictability are crucial to constrain uncertainty not just in decadal to centennial climate change predictions, but also for how other sensitivity experiments are undertaken and analysed. Decadal prediction models demonstrate the importance of accurate initialisation of the ocean surface and sub-surface (Haines et al., 2010). However, feedbacks between the land surface and ocean decadal variability are an additional important factor that have not thus far been examined to the same degree.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Dr Joy Singarayer

Desert dust and ancient oceans: Implications for climate and atmospheric CO2

Desert dust is the main source of the iron which is required by living organisms in the ocean. Insufficient supply of iron limits marine life in large parts of the ocean and reduces the ability of the ocean to regulate atmospheric CO2, and therefore our climate (Jickells et al., 2005). While there is relatively good knowledge of the role of desert dust in controlling the modern ocean biological pump, it is still unclear what might happen in a warming climate. Examining the past period of the Cretaceous (145 to 65 million years ago) can help, because of its relatively warm climate, which occurred as a result of high atmospheric CO2 at that time.

This project comes with an augmented student stipend consisting of an additional £1000 per year provided by the project CASE partner, GETECH.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Dr Dan Lunt

An analogue for the potential future collapse of the West Antarctic ice sheet?

This studentship aims to understand the reasons for the rapid collapse of the Barents Sea ice sheet at the end of the last Ice Age (~14 kyr BP). This aim is important because the Barents Sea ice sheet is an excellent natural analogue to the present-day, marine ice sheet covering West Antarctica. Understanding the cause of the known collapse of the Barents Sea ice sheet may therefore allow us to assess the circumstances under which the West Antarctic ice sheet could collapse and the rate at which such a collapse could occur.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Prof Tony Payne

Palaeoenvironmental controls on the accumulation of hydrocarbon source rocks in Paratethys: insights from sedimentology and geochemistry

The Black Sea, Caspian Sea and Aral Sea are the remnants of a much larger marine seaway, Paratethys, which stretched from Germany to China at the beginning of the Oligocene. Over the next 30 million years, Paratethys progressively shrank as a result of a combination of basin infill, glacio-eustatic sea-level lowering and tectonic uplift. Its increasingly epicontinental character generated a high amplitude record of environmental change including periods of anoxia, hypersalinity, fresh water conditions and desiccation events. This project will focus on the early period of Paratethyan history, when gateway restriction led to deposition of organic-rich calcareous and diatomaceous hydrocarbonproducing black shales, known as the Maikop Series. The aim of this project is to understand the controls on Paratethyan-wide anoxic conditions through detailed sedimentology and multi-proxy isotope (e.g. Sr, Nd) and organic geochemistry.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Dr Rachel Flecker

Australian monsoon and ENSO records from Papua New Guinea

Papua New Guinea sits within the Western Pacific Warm Pool - the region of warmest ocean surface waters and the most intense atmospheric convection on Earth. This region is the site of massive energy exchange that drives global atmospheric circulation and so any changes in the warm pool can have profound effects on climate around the globe. We see this influence every 2 to 7 years during El Niño events. One of the key unknowns in predicting future climate variability is how the El Niño Southern Oscillation (ENSO) phenomenon, and the background state of the Western Pacific Warm Pool, will respond to global warming. ENSO also interacts with the Asian-Australian monsoon circulation, but the relationship is both inconsistent and poorly understood. With over 800 million people from across India, South-east Asia to Australia directly dependent on the stability and onset of these monsoonal rains, predicting how it will behave in a warmer world is also critical.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Dr David Richards

Developing effective model diagnostics of competing rainfall runoff processes by quantifying observational uncertainties and improving model performance metrics

One of the holy grails of modern hydrology is to develop better methods to diagnose where rainfall-runoff model structures are deficient in predicting streamflow and therefore identify improvements to their conceptualisation and hence their predictive capability. This is a non-trivial problem because inherent uncertainties exist in the observational data sets used to drive and evaluate competing model structures (Beven and Freer, 2001; Freer et al., 2004). Recent advances in this area have developed methods for including observational errors more explicitly in model performance measures and dealing with some of the non-stationarity in these errors (Liu, et al., 2009; McMillan et al., 2010). This has led to new ways in which we can assess competing model structures of rainfall-runoff processes in an uncertainty analysis framework (Krueger, et al., 2010). However, further work is still to be done to develop methods that diagnose competing model structures effectively. We believe this requires two main points of development at this time, 1) How to characterise the potential input uncertainty of precipitation data and 2) The development of timestep based scores and post analysis techniques to quantify the consistency or inconsistency in where models fail to reproduce observed behaviour.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Professor Jim Freer

Mapping ice sheet properties from the CryoSat mission

The Antarctic and Greenland ice sheets contain around 90% of the world’s freshwater. If they were to melt completely they would raise global sea level by some 65 m. In the last two decades satellite observations have identified significant changes in the flow, mass balance and grounding lines of large sectors of both ice sheets [Pritchard et al., 2009; E Rignot et al., 2011; E Rignot et al., 2008; E J Rignot, 1998]. Most of these satellite missions have now ended, however. Although we have learnt a great deal from previous satellite altimeter missions about topography [Bamber et al., 2009], grounding lines [Brunt et al., 2010] and mass balance [Zwally et al., 2005] they had significant limitations in terms of spatial and temporal coverage, accuracy and instrument performance.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Professor Jonathan Bamber

Improved models of water quality behaviour for evaluating monitoring strategies, prediction uncertainties, and to support decision-making

The availability of data from the appropriate place and collected at appropriate times is crucial to support and develop understanding of environmental processes. It also provides the evidence base from which decision-makers formulate and implement policy and subsequent regulation. But it is prohibitively expensive to monitor everything, everywhere. This is particularly the case for continuous monitoring of river water chemistry, so routine water samples are often available at only a low resolution in both space and time. However these data are still used to support environmental management and local through to national decision-making.

Start date: 1st October 2013 (flexible)

Closing date for applications: 4th January 2013

Further information available

Contact: Professor Jim Freer