Overview

Project Highlights:

  • First convection resolving simulations of multiple time periods for the Amazon region
  • Potential for transformative insight into how the climate system will respond to ongoing warming and deforestation
  • Important contribution to understanding how and where the Amazon rainforest may have survived CO2-starvation during the last ice-age.

The Amazon basin contains the world’s largest rainforest. Dubbed the ‘lungs of the Earth’, this biome sequesters vast amounts of carbon dioxide and hosts countless species of flora and fauna. Human activities are endangering this irreplaceable ecosystem, with potential consequences not only for biodiversity and local inhabitants, but also the global carbon cycle and climate (Gedney & Valdes, 2000).

One influential early study with a global coupled climate-vegetation model predicted a drier Amazon, driving forest contraction and a self-amplifying die-back, resulting in the conversion of the whole region to savannah (Cox et al., 2000). More recent studies tend to predict less extreme reductions in rainfall but with substantial uncertainties (Huntingford et al., 2013).

Climate changes in Earth’s history offer complementary lessons on the response of the climate system. During the peak of the ice-age (the Last Glacial Maximum or LGM) a globally cooler climate characterised by lower levels of atmospheric CO2, implied serious stresses for the forests. However, paleo-climate evidence suggests that the Amazon rainforest survived, at least in the Eastern lowlands (Wang et al., 2017). This implies a lower limit on the rainfall during this time. However, climate simulations of the LGM do not agree on whether it was drier or wetter.

More widely, the simulation of convective rainfall -the process responsible for the majority of rainfall in the tropics, has important biases. Global climate models underestimate heavy downpours, have the wrong daily timing of rainfall over land, and have difficulty in reproducing the seasonal changes in monsoons (Dai et al 2006, Marsham et 2013). Over the Amazon, Anber et al (2015) found that daily to seasonal cycles in deep convection and fog contribute substantially to the mean state, yet these processes are represented poorly if at all, in conventional global models. This means that our understanding of the past and future Amazonian hydrological cycle may contain substantial errors.

This study will use the high-resolution Met Office atmosphere model to address this situation and investigate the response of the Amazon hydrological cycle to past and future conditions, providing new insight into the Amazon’s vulnerability to multiple environmental stresses.

Dry-season clouds observed over the Amazon from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS).

Methodology

In this project will produce high-resolution climate simulations covering the Amazon for the present day, the Last Glacial Maximum and for a hypothetical high-CO2 future climate state. The simulations will make use of the Met Office’s Nesting suite to investigate how moving to very high (~1.5km) horizontal resolution and thereby directly resolving convective storms, alters our understanding of the hydrological cycle in this critical region. Simulations of the Last Glacial Maximum will make use of global model simulations from CMIP6/PMIP4 and will be among the very first convection –resolving simulations of the ice-age. We will investigate how the underlying vegetation alters the coupling of the hydrological cycle. This will involve testing different models of forest structure and extent for the past and future climate states, driven by the latest palaeo-ecological reconstructions (e.g. Marchant et al 2009, Haggi et al 2017) and by state-of-the-art land surface modelling.

 

Training and Skills

This project will give the student direct experience of high-performance computing and using the Met Office’s Unified Model, which is a state-of-the-art climate and weather forecast suite. During the project the student will receive training in understanding and evaluating complex systems, in climate dynamics and meteorology and computer programming and mathematical analysis.

Timeline

Year 1: Develop convection permitting simulation of present day, evaluate against satellite observations. Devise past and future scenarios based on global climate modelling, vegetation reconstructions and model projections of future vegetation change.

Year 2: Configure convection permitting simulations of the Last Glacial Maximum and a representative warm future state. Begin analyses and comparisons with observations.

Year 3: Analyse the mechanisms of the change in the hydrological cycle and evaluate with available reconstructions from the past and compare with the state-of-the-art in global modelling.

Partners and collaboration (including CASE)

The project’s supervisors will be Dr Peter Hopcroft who researches climate change past and future using global and regional climate models, Dr Martin Widmann whose research focusses on climate downscaling and assimilation, and Dr Tom Pugh, who is an expert in terrestrial vegetation modelling. Collaboration through international projects including PMIP4 and CMIP6 will be encouraged.

Further Details

Please contact Dr Peter Hopcroft, School of Geography, Earth & Environmental Sciences, University of Birmingham for further details about this project. Email: p.hopcroft@bham.ac.uk, telephone: 0121 414 6167.