Volcanic eruptions are driven by the formation and growth of bubbles in magma. The timing of bubble formation and the rate of bubble growth control the type of the eruption, and determine the nature of eruption products. We need to understand bubble nucleation and growth in order to meet one of the grand challenges in volcanology: forecasting the onset, size, duration, and resultant hazards of explosive eruptions. We will conduct new experiments that replicate the conditions inside the sub-volcanic plumbing system, and will measure the characteristics of the bubbles that form as we vary those conditions. We will use the results to create new computational models for bubble formation and link those to existing models for bubble growth. This will create a general tool that will allow the volcanology community to predict the conditions under which bubbles form in magma as it rises to the surface, and the rate at which the bubbles grow. These models will help us to predict how magma will behave during volcanic eruptions, and to interpret the materials that are erupted.

In April 2016, the Pedernales Earthquake ruptured an ~ 130 km long, 100 km wide segment of the subduction zone along the coast of Ecuador in a Mw 7.8 megathrust event. Immediately after the earthquake a coordinated international rapid response effort deployed 48 broadband and intermediate period seismometers and 10 ocean bottom seismometers above the rupture zone and adjacent fault segments where large earthquakes occur on decadal time scales and slow slip events have been observed. The seismic array is complemented by rapid response geodetic efforts and long term observations from permanent national seismic and geodetic networks in Ecuador. We will use subduction of the Nazca Plate beneath Ecuador and the Pedernales Earthquake and aftershock sequence to link along strike variations in structure and seismic properties to the distribution of slip behaviors observed (pre-, co- and post-seismic) to determine the relationship between slow slip and megathrust rupture. We will integrate analyses from a variety of broadband seismic techniques to examine the persistence of asperities for large to great earthquakes over multiple seismic cycles, the role of asperities in promoting or inhibiting rupture propagation, and the relationship between locked and creeping parts of the subduction interface.

The nature of future human induced climate change is highly uncertain with projected global temperature increases in 2100 spanning 0.3-6.4 Celsius (IPCC 2007, AR4). Part of this large uncertainty is due to the paucity of climate & proxy-climate data to validate climate models & constrain Earth System sensitivity to simulated forcing, particularly in the Southern Hemisphere (SH). A key component of variability of the SH atmosphere is the Southern Annular Mode (SAM), which is an oscillation of atmospheric mass that results in changes in the westerly winds over the Southern Ocean. The SH westerly winds modify the upwelling of carbon-rich deep water & therefore influence the global balance of carbon dioxide between the ocean and the atmosphere. It is uncertain whether the recently observed intensification of the southern westerlies will cause the Southern Ocean to be a net source or sink of atmospheric carbon dioxide. Little is known about the long-term past variability of the southern westerlies & atmospheric carbon dioxide, making it difficult to separate internally & externally-forced fluctuations. It is imperative to rectify this deficiency in order to generate & test hypotheses to explain the processes of change in the strength of the southern westerlies & how these are related to (inter-)hemispheric climate change during known periods of contrasting climate change, for example the Medieval Climatic Anomaly & the Little Ice Age. This project will investigate four new sites located in southern South America (SSA). This region is located in the core of the southern westerlies and is ideally located to capture changes in their intensity. SSA terrestrial peatland-based palaeoclimate archives are capable of recording long-term changes in the westerlies, given that wind intensity affects precipitation mainly produced in winter by fronts & low-pressure systems embedded in the prevailing westerly circulation. The selected sites are all rain-fed peat bogs, which provide excellent climate archives. Plant & protozoan (testate amoebae) fossils preserved in well-dated cores extracted from these bogs will be used to reconstruct past changes in Bog Surface Wetness (BSW, an index of surface water balance) over the last ~2000 years, at a time resolution of 10-100 years. The same core samples will be analysed for stable isotopes of oxygen & hydrogen. The spatial & temporal distribution of the heavy isotopes of these elements in precipitation is related to air temperature, & hence to atmospheric circulation. The isotope signal captured in the cellulose fraction of Sphagnum moss closely tracks that of the precipitation used by the plant for cellulose synthesis. Hence, fossil Sphagnum from raised peat preserves a clear signal of past changes in climate & atmospheric circulation. The stable isotope data will be compared with isotope measurements from moss banks & ice cores from the maritime Antarctic and Antarctic Peninsula, in addition to stable water isotope data & BSW reconstructions from eastern North America. Analyses of fossils & stable isotopes from the same core levels will allow us to reconstruct the timing, magnitude & spatial pattern of the regional terrestrial response, as well as exploring the impact of different causal factors such as changes in atmospheric & ocean circulation & solar variability on the climate of the study area. In this way, insight will be gained into the mechanisms that have driven climate change over the last ~2000 years. Hypotheses to be tested: 1 Climate changes during the last ~2000 years in SSA are in phase with climate changes identified in eastern North America & NW Europe, & represent inter-hemispheric teleconnections. 2 Climate changes in SSA during the last ~2000 years are in antiphase with Northern Hemisphere climate changes & represent a bipolar seesaw. 3 Climate changes in SSA during the last ~2000 years are uncorrelated with Northern Hemisphere climate changes.

Future climate change is one of the most challenging issues facing humankind and an enormous research effort is directed at attempting to construct realistic projections of 21st century climate based on underlying assumptions about greenhouse gas emissions. Climate models now include many of the components of the earth system that influence climate over a range of timescales. Understanding and quantifying earth system processes is vital to projections of future climate change because many processes provide 'feedbacks' to climate change, either reinforcing upward trends in greenhouse gas concentrations and temperature (positive feedbacks) or sometimes damping them (negative feedbacks). One key feedback loop is formed by the global carbon cycle, part of which is the terrestrial carbon cycle. As carbon dioxide concentrations and temperatures rise, carbon sequestration by plants increases but at the same time, increasing temperatures lead to increased decay of dead plant material in soils. Carbon cycle models suggest that the balance between these two effects will lead to a strong positive feedback, but there is a very large uncertainty associated with this finding and this process represents one of the biggest unknowns in future climate change projections. In order to reduce these uncertainties, models need to be validated against data such as records for the past millennium. Furthermore, it is extremely important to make sure that the models are providing a realistic representation of the global carbon cycle and include all its major component parts. Current models exclude any consideration of the reaction of peatlands to climate change, even though these ecosystems contain almost as much carbon as the global atmosphere and are potentially sensitive to climate variability. On the one hand, increased warmth may increase respiration and decay of peat and on the other hand, even quite small increases in productivity may compensate for this or even exceed it in high latitude peatlands. A further complication is that peatlands emit quite large quantities of methane, another powerful greenhouse gas. Our proposed project aims to assess the contribution of peatlands to the global carbon cycle over the past 1000 years by linking together climate data and climate model output with models that simulate the distribution and growth of peatlands on a global scale. The models will also estimate changes in methane emissions from peatlands. In particular, we will test the hypotheses that warmth leads to lower rates of carbon accumulation and that this means that globally, peatlands will sequester less carbon in future than they do now. We will also test whether future climate changes lead to a positive or negative feedback from peatland methane emissions. To determine how well our models can simulate the peatland-climate links, we will test the model output for the last millennium against fossil data of peat growth rates and hydrological changes (related to methane emissions). To do this, we will assemble a large database of published information but also new data acquired in collaboration with partners from other research organisations around the world who are involved in collecting information and samples that we can make use of once we undertake some additional dating and analyses. Once the model has been evaluated against the last millennium data, we will make projections of the future changes in the global carbon cycle that may occur as a result of future climate change. This will provide a strong basis for making a decision on the need to incorporate peatland dynamics into the next generation of climate models. Ultimately we expect this to reduce uncertainty in future climate change predictions.

Past terrestrial responses to climate-ocean interactions in the North Atlantic region are a critical research priority because they show how changes in key aspects of climate that will be affected by future global warming, such as ice sheet volume & ocean circulation, may be translated into phenomena of socio-economic importance, including the atmospheric water balance & soil moisture availability. Although we are beginning to understand the nature & magnitude of changes in the circulation of the North Atlantic over the last 10,000 years, terrestrial responses to these events are still poorly understood in terms of timing, magnitude & spatial pattern. It is imperative to rectify this deficiency in order to generate & test hypotheses to explain the processes of change, to understand the strength of relationships between oceanic & terrestrial climate change, & to enable future soil conditions & water resources to be predicted using computer models. Plan of work This project will investigate four sites located on a transect along the eastern seaboard of North America, from northern Newfoundland to Maine. This region was highly sensitive to past changes in ice sheet mass balance & ocean circulation. The selected sites are all raised (rain-fed) peat bogs, which provide superb climate archives. Plant & animal (testate amoebae) fossils preserved in well-dated cores extracted from these bogs will be used to reconstruct past changes in Bog Surface Wetness (an index of surface water balance) over the last 8500 years, at a time resolution of 10-100 years. The same core samples will be analysed for stable isotopes of oxygen & hydrogen. The spatial & temporal distribution of the heavy isotopes of these elements in precipitation is related to air temperature, & hence to atmospheric circulation. The isotope signal captured in the cellulose fraction of Sphagnum moss closely tracks that of the precipitation used by the plant for cellulose synthesis. Hence, fossil Sphagnum from raised peat preserves a clear signal of past changes in climate & atmospheric circulation. Modern precipitation along the eastern seaboard of North America is derived mainly from the Atlantic Ocean. A strong temperature contrast exists between the Arctic waters of the Labrador Current, which flows southwards along this coast, & the warm waters of the Gulf Stream further offshore. Past isotopic ratios in precipitation falling over coastal areas will have been strongly influenced by changes in these ocean currents & in the heat transport by the Gulf Stream. By combining the oxygen & hydrogen isotope records, we will estimate the deuterium excess, an index of the conditions prevailing at the sea surface when evaporation occurred, including the extent of sea ice. The stable isotope data will be compared with isotope measurements on ice cores from Greenland & Canadian ice caps, and more cautiously, with estimated isotope values for surface seawater & lakes that have been derived from sediment analyses. Hence, analyses of fossils & stable isotopes from the same core levels will allow us to reconstruct the timing, magnitude & spatial pattern of the terrestrial response, as well as exploring the impact of different causal factors such as meltwater discharges, changes in atmospheric & ocean circulation & solar variability on the climate of the study area. In this way, insight will be gained into the mechanisms that have driven climate change over the last 8500 years. Hypotheses to be tested: 1) Between 8500 & 6800 years ago, the climate of the study area was strongly influenced by repeated discharges of glacial meltwater from the decaying North American Ice Sheet to the north, resulting in cooling & increased bog wetness. 2) After the disappearance of the ice sheet, 6800 years ago, the climate of the study area was indirectly influenced by cyclical variations in sea ice extent, ocean currents & deepwater formation north of Iceland.