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 large-scale changes in earth's climate, prior to modern climate change, were the Pleistocene glacial cycles, which feature growth and disintegration of large ice sheets, rapid shifts in major rain belts, and abrupt changes in ocean circulation. Changes in atmospheric CO2 concentrations, reconstructed from air bubbles in ice cores, are intimately linked with these ice age climate events. Indeed the close coupling of CO2 and temperature over glacial-interglacial cycles has become an iconic image in climate science, a poster child for the importance of CO2 in climate, and the natural template against which to compare current man-made CO2 rise.
However despite the high profile of glacial-interglacial CO2 change, we still don't fully understand its cause. The leading hypotheses for glacial CO2 change involve increased CO2 uptake by the ocean during ice ages, which is vented to the atmosphere during deglaciation. However despite decades of work these hypotheses have had few direct tests, due to a lack of data on CO2 storage in the glacial ocean. One of the most glaring holes in our understanding of ice age CO2 and climate change is the behaviour of the Pacific. This basin contains half of global ocean volume, and ~30 times more CO2 than the atmosphere, and so its behaviour will have global impact. It has also recently been suggested that the North Pacific may play an active role in deglacial CO2 rise, with local deep water formation helping to release CO2 from the deep ocean to the atmosphere. If correct, this hypothesis provides a new view of Earth's climate system, with deep water able to form in each high latitude basin in the recent past, and the North Pacific potentially playing a pivotal role in deglaciation. However few data exist to test either the long-standing ideas on the Pacific's role in glacial CO2 storage, nor the more recent hypothesis that North Pacific deep water contributed to rapid deglacial CO2 rise. Given the size of the Pacific CO2 reservoir, our lack of knowledge on its behaviour is a major barrier to a full understanding of glacial-interglacial CO2 change and the climate of the ice ages.
This proposal aims to transform our understanding of ice age CO2 and climate change, by investigating how the deep North Pacific stored CO2 during ice ages, and released it back to the atmosphere during deglaciations. We will use cutting-edge geochemical measurements of boron isotopes in microfossil shells (which record the behaviour of CO2 in seawater) and radiocarbon (which records how recently deep waters left the surface ocean), on recently collected samples from deep ocean sediment cores. By comparing these new records to other published data, we will be able to distinguish between different mechanisms of CO2 storage in the deep Pacific, and to test the extent of North Pacific deep water formation and CO2 release during the last deglaciation. We will also improve the techniques used to make boron isotope measurements, and add new constraints on the relationship between boron isotopes and seawater CO2 chemistry, which will help other groups using this technique to study CO2 change. To help us understand more about the mechanisms of changes in CO2 and ocean circulation, and provide synergy with scientists in other related disciplines, we will compare our data to results from earth system models, and collaborate with experts on nutrient cycling and climate dynamics. Our 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.

1. Workshop on ice age climate change delivered to schools through Geobus (Secondary school students and teachers):

Secondary school students, teachers, and their families will benefit from educational outreach that we will undertake as part of the University of St Andrews' Geobus initiative. Geobus provides teaching and resources in the earth and environmental sciences to secondary schools across Scotland and the North of England. We will develop a Geobus workshop on ice age oceans and climate change, showing how high-school level physics and chemistry may be applied to understand ocean-atmosphere CO2 exchange, global albedo, and deep ocean circulation. The topical nature of climate change makes it an excellent topic with which to engage students in STEM subjects, a key goal for UK education and economic development.

2. Edinburgh Science Festival (General public-children and families; adults):


Building on the workshop developed with the expertise of the Geobus team, we will apply to bring a workshop on ice age climate change to the Edinburgh Science Festival. This will feature hands-on experiments that teach the fundamental science underpinning climate change past and present. We will pitch a project that uses CO2 and pH loggers, water tanks, and floating candles to measure the effect of burning fossil fuels on CO2 in the atmosphere and the ocean. PI Rae will also give an evening lecture to adults on the science of deglaciation, featuring drink mixing of different colours and densities to simulate ocean circulation, and ice input to simulate different sea level rise scenarios.

3. Improved scientific understanding of the climate system (Climate scientists, policy makers, and their constituents):

This project will provide new insights into ocean-atmosphere CO2 exchange, links between changes in rainfall and abrupt changes in ocean circulation and climate, and deglaciation of major ice sheets. These components of the climate system have the potential to change rapidly in the next few hundred years, so improved knowledge of how they can operate, and of any potential 'tipping points' in the climate system, is required by policy makers for the benefit of the general public. To ensure effective dissemination of our research results throughout the climate science field, PI Rae will organise a session at the AGU fall meeting in year two of this project, in collaboration with our project partners. To establish a direct link with policy makers, PI Rae will meet with the Member of Parliament for NE Fife, to discuss the science underlying anthropogenic climate change.

4. Climate change teaching moments (General Public and Policy Makers):

The proposed research covers a broad range of topical climate topics, providing excellent teaching moments to engage with the general public. We will use the St Andrews press office to help disseminate our key findings, and their relationship to modern climate change, to the media. PI Rae's recent paper on this topic was effectively publicised in this way, making the front page of the Herald, and garnering coverage in the Times of India, the Daily Mirror, and Daily Mail. PI Rae will also maintain an active blog on this research on his group website, and promote the project's progression on Facebook and Twitter. PI Rae is an active tweeter and will continue to use this platform as a means to reach a broad audience.

5. Training of young researchers (Young researchers and UK STEM community):

The project will train two undergraduate students in laboratory techniques, research methods, and scientific writing, with impact assessed through a project report, and inclusion on manuscripts. The project will also train a PDRA in radiocarbon and boron isotope analyses. The multi-disciplinary nature of this project, with involvement of a strong and diverse network of project partners, will further enhance the PDRA's training and career deve