INTRIGUED: INvestigating The Role of the North Pacific In Glacial and Deglacial CO2 and Climate

The geological record offers an invaluable window into the different ways earth's climate can operate. The most recent major changes in earth's climate, prior to modern climate change, were the Pleistocene ice ages. These feature growth and collapse of massive ice sheets, rapid shifts in rain belts, and abrupt changes in ocean circulation. Changes in atmospheric CO2 are intimately linked with these ice age climate changes, but despite decades of effort, we still don't fully understand their driving mechanisms.

The aim of the newly NERC-funded research by Dr James Rae of the Department of Earth and Environmental Sciences is to transform our understanding of ice age CO2 and climate change, by investigating how the deep Pacific stored CO2 during ice ages, and released it back to the atmosphere during deglaciation. Although all leading hypotheses for ice age CO2 change involve CO2 storage in the deep ocean, the role of the Pacific remains unknown. As the Pacific contains half of global ocean volume, and ~30 times more CO2 than the atmosphells, whichere, its behaviour will have global impact. Our work will involve making geochemical measurements on fossil shells taken from sediment cores from the deep Pacific Ocean. These shells - called foraminifera - record the chemistry of the surrounding water at the time they grow, so by making measurements on them down the length of a sediment core, we can read back through the history of ocean circulation and CO2. A particular focus of our grant is the boron isotope composition of these sh reflects ocean pH and CO2. The new St Andrews Isotope Geochemistry labs at the University of St Andrews are among the first in the world to have be built fully boron-free, allowing us to be at the forefront of this cutting-edge technique.

The research is based at St Andrews, but features a team of leading scientists from around the world, including the Universities of Bristol, Kiel, Oregon, McGill, and ETH Zurich, the Woods Hole Oceanographic Institute and Scripps Institute of Oceanography USA, the Alfred Wegner Institute for Polar Research Germany, and radiocarbon facilities in Glasgow and California.

The project will ultimately improve understanding of CO2 exchange between the ocean and the atmosphere, which is an important factor for predicting the path of future climate change.

Tree rings unveil temperatures of the last millenium

High on mountains across Alaska, Canada, Europe and Russia near the upper or high latitude tree line, even the hardiest of conifers are at the edge of survival. Their annual rings tell a story of extreme cold that limit their growth and of warmer years that allow them to flourish. By analysing samples from these living trees and fallen timbers, researchers are able to reconstruct past temperature change.

A new international consortium of scientists, led by Dr Rob Wilson of the Department of Earth & Environmental Sciences, has collated a network of such tree-ring archives to derive a history of temperature fluctuations across the entire Northern Hemisphere. The N-TREND consortium (N-TREND stands for Northern Tree-Ring Network Development) was created to develop a global database of tree-ring research that improves on previous efforts for developing large-scale temperature reconstructions across the hemisphere. The consortium was devised to provide a collective platform where participants are all on the same page with respect to identifying not only gaps in the hemispheric network, but also facilitating the communication and training of new methodological approaches that can further improve tree-ring based temperature reconstructions.

The consortium’s first research paper, appearing in the current issue of Quaternary Science Reviews, provides a view of past Northern Hemisphere temperature changes over more than 1,000 years. It reveals a longer and warmer Medieval period than previous temperature reconstructions suggested, from around 850 to the end of the 11th century, with a peak in the 1160s. It also shows how the two coldest decades—1812-1821 and 1832-1841, both during a period known as the Little Ice Age—are followed by near continuous warming until present. The new paper takes a close look at some of the challenges of previous historic temperature reconstructions, explaining why reconstructions using multiple proxy archive sources—such as tree rings, ice cores, lake sediments etc, or mixing seasons expressed by different archives — can end up with ambiguous results when trying to understand past climatic variability and forcing.
A second paper will soon be submitted that will look at spatial temperature variations across the Northern Hemisphere for the last millennium. Such spatial analyses will help answer questions about the spatial extent of Medieval Warm Period, for example, and through comparative analyses with global climate models could help attribute the forces behind such past temperature ch
ange.

Columbia University links: Lamont-Doherty Earth Observatory, Blog
"Last millennium northern hemisphere summer temperatures from tree rings: Part I: The long term context", Quaternary Science Reviews Volume 134, 15 February 2016, Pages 1–18, doi:10.1016/j.quascirev.2015.12.005

International collaboration produces atlas of Europe’s paleoclimate

St Andrews Researcher, Dr Rob Wilson (Senior Lecturer, Department of Earth and Environment Sciences), is involved in an international collaboration led by Professor Edward Cook at Columbia University using tree rings to produce a new paleoclimate atlas of past European drought.

To date, the long history of severe droughts across Europe and the Mediterranean has largely been told through historical documents and ancient journals, each chronicling the impact in a geographically restricted area. Now, for the first time, an atlas, based on tree-ring data, maps the reach and severity of dry and wet periods across Europe and parts of North Africa and the Middle East over the past 2,000 years.

This new data-set for Europe will complement two previous drought atlases covering North America and Asia allowing scientists to pinpoint causes of drought and extreme rainfall in the past and identify patterns that could lead to better climate model projections for the future. The new atlas could also improve understanding of climate phenomena like the Atlantic Multi-decadal Oscillation, a variation in North Atlantic sea-surface temperatures that hasn’t been tracked long enough to tell if it is a transitory event, forced by human intervention in the climate system, or a natural long-term oscillation.

The importance of understanding past climate change and its impact on human society cannot be underestimated.  For example, an unusually cold winter and spring are often blamed for the 1740-1741 famine in Ireland. The Old World Drought Atlas points to another contributor: rainfall well below normal during the spring and summer of 1741. The atlas shows how the drought spread across Ireland, England and Wales.

The atlas also tracks the reach of the great European famine of 1315-1317, when historical documents describe how excessive precipitation across much of the continent made growing food nearly impossible. The atlas tracks the hydroclimate across Europe and shows its yearly progressions from 1314 to 1317 in detail, including highlighting drier conditions in southern Italy, which largely escaped the crisis.

More information on The University of St Andrews Tree-Ring Laboratory can be found here: https://www.st-andrews.ac.uk/~rjsw/TRL/

Research Publication:  Cook et al. (2015). Old World megadroughts and pluvials during the Common Era. Science Advances. 1 (11). e1500561. DOI: 10.1126/sciadv.1500561

The Southern CO2 that helped end the ice age

Scientists have long puzzled over the processes that caused CO2 to rise and help end the last ice age. Leading theories have involved increased CO2 release from the deep ocean around Antarctica, but there has been no direct evidence to prove this happened.

Our study used the geochemistry of tiny planktonic fossil shells to reconstruct the amount of CO2 in waters around Antarctica during the end of the last ice age.  We were able to show, for the first time, that CO2 was indeed released from the Southern Ocean to the atmosphere, helping warm the planet and melt back the ice sheets that would have covered Scotland and much of the rest of Northern Europe and America.

Dr James Rae, of the Department of Earth and Environmental Sciences, who co-authored the study, said “intervals of CO2 and climate change in the past offer a fantastic opportunity for us to better understand the path of future climate.  As the ocean currently takes up about a third of the CO2 emitted by humans, it’s important to understand the controls on CO2 exchange between the ocean and the atmosphere so we can predict how ocean CO2 uptake may change in the future.  It’s also striking to think that CO2 change has contributed to climate changes in the past as dramatic as melting back a mile of ice on top of Scotland, and you’ve got to wonder what adding the same amount of CO2 to the atmosphere, but 100 times faster, will do to climate in the years to come.” [Nature 518, 219–222 (12 February 2015) DOI: 10.1038/nature14155, "Boron isotope evidence for oceanic carbon dioxide leakage during the last deglaciation"] [press release]

Tree ring data enhances understanding of millennial scale climate change

A team of international scientists, including Dr Rob Wilson of the Department of Earth and Environmental Sciences, has published a reconstruction of past summer temperatures for northern Europe reaching back to 138 BC based on the information provided by tree-rings. Researchers from Germany, Finland, Scotland, and Switzerland examined tree-ring density profiles in trees from Finnish Lapland. In this cold environment, trees, when they die, often fall into one of the numerous lakes, where they remain well preserved for thousands of years. The researchers were thus able to create a temperature reconstruction of unprecedented quality using many hundreds of samples. The reconstruction provides a high-resolution representation of summer temperature patterns in the Roman and Medieval Warm periods, but also shows the cold phases that occurred during the Migration Period and the later Little Ice Age.

Dr Wilson sampling a tree in Finland. 

In addition to the cold and warm phases, the new climate curve also exhibits a phenomenon that was not expected in this form. For the first time, researchers have now been able to use the data derived from the density data to precisely capture a much longer-term cooling trend that has been playing out over the past 2,000 years. Their findings demonstrate that this trend involves a cooling of -0.3°C per millennium due to gradual changes in summer insolation related to the position of the sun and an increase in the distance between the Earth and the sun. This long-term trend, however, is not seen in the more traditionally used ring-width parameter - measured from the same samples.

These findings suggest that large-scale near-surface air-temperature reconstructions, relying predominantly on ring-width data, may underestimate pre-instrumental temperatures including warmth during Medieval and Roman times. [Nature article]. Dr Wilson is leading a similar project based in the Scottish Highlands.

St Andrews Communities Working Together

Transition University of St Andrews and St Andrews Environmental Network (StAndEN) have joined forces to bring a unique initiative to the town and gown communities of the St Andrews area to reduce carbon emissions and to build community resilience. The St Andrews Communities Working Together partnership has been successful in securing funding  of £347,770 from the Scottish Government's Climate Challenge Fund (CCF) for a three-year project. Over this time, the partnership will run projects that focus on energy use in homes, community gardens, consumption of sustainable foods, a local exchange trading scheme and engaging individuals in practical responses to climate change. The collaboration of town and gown celebrates and shares the wealth of knowledge and experience of the St Andrews community as a whole in tackling climate change. See here the full list of CCF-funded projects.