Rapid | Climate Change | ||||||||||||||||||||
International Science Conference | |||||||||||||||||||||
24 - 27 October 2006. Birmingham, U.K. | |||||||||||||||||||||
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CONTENT
Background: The NERC RAPID Programme
Important questions addressed at the conference:
- Rapid climate changes have occurred in the past - but can they occur in the future?
- Is the Atlantic overturning circulation slowing down?
- Will Greenland ice melt shut down the THC?
- Are we at risk?
Note: Photos and other illustrations relevant to each of these questions are available below.
Background: The NERC RAPID Programme
Many models predict that rapid (decadal-scale) climate change could occur during this century as a consequence of global warming. The Natural Environment Research Council (NERC) has consequently made a £20M investment to investigate and understand the causes of rapid climate change - the RAPID programme (2001-2008) - with a main focus on the role of the North Atlantic. Beyond vastly improving scientific understanding and prediction, RAPID is designed to deliver an assessment of the probability and magnitude of future rapid climate change, and scenarios that can be used in risk assessments by those studying the impacts of climate change.
The RAPID programme has established a UK lead in this science in the international arena, driving the creation of new collaborative programmes with the USA (NSF, NOAA) and Dutch and Norwegian Research Councils, so drawing millions of pounds of additional investment into the research area. Early results from the programme have indicated that a major reorganisation of the Atlantic circulation may already be underway, and have aroused wide debate.
The Birmingham conference explores current scientific understanding of rapid climate change, with a sharp focus on the role of the Atltanic Meridional Overturning Circulation (MOC) in such change. It brings together the international community of scientists studying rapid climate change through oceanographic observations, palaeo studies and climate modelling in order to discuss recent research findings and identify outstanding problems. The meeting also explores the impacts of THC change on weather, climate and society, and will showcase emerging results from the NERC-RAPID programme.
Important questions addressed by the conference
The scientific papers at the conference address a number of important questions that have to be answered before we can assess the risk to North-West Europe arising from possible rapid climate change. Four of these are covered briefly below, based on a selection of the scientific papers presented at the conference.
Illustrations: The photos and other illustrations shown as thumbnails under each section below are available at high resolution by following the links underneath each image. A short caption explaining each illustration is available by clicking on the thumbnail.
Selected abstracts: A selection of relevant abstracts may be found at the end of each section, with a link to the abstract itself in a pop-up window. Other abstracts may be found using the Abstract search. Please note that all posters will be on display throughout the conference.
Rapid changes have occurred in the past, but can they occur in the future?
Talks: Tuesday 24th, p.m. Posters: Wednesday 25th, p.m.
Very rapid changes in climate, especially around the North Atlantic region, have certainly occurred in the past, probably associated with changes in ocean heat transport. Several papers at the meeting address this. They show that it is possible for climate to shift rapidly (in decades) by several degrees between different climate states. The existence of large ice sheets over North America seems to have been a prerequisite for these large changes, so that similar jumps cannot be triggered by the same means today. However, such events have given an opportunity to study how climate behaves when ocean circulation is changed, and assess whether models can capture such behaviour.
Climate jumps occurred numerous times during the last glacial period, when irregular supplies of freshwater and ice to key regions of the North Atlantic changed the speed and style of ocean circulation. The most recent and relevant of these events occurred 8200 years ago, and probably arose from the outburst of a lake from behind the dwindling North American ice sheet. As several papers show, this event is the outstanding climate change of the last 10,000 years. It can be seen as an extreme cooling (of around 6°C at Greenland, less severe in Europe), lasting for 1-2 centuries (Wolff). New records presented here show clearly how it changed climate in Greenland (Thomas), Europe (Holmes), and eastern North America (Daley). New evidence from ocean cores (Chapman) reveals some details of the sequence of events from the pulse of freshwater to the ocean to the related climate change, and climate models can reproduce some aspects of the change (Legrande, Otto-Bliesner).
Selected abstracts:
Chapman M.R., E. Farmer, K.R. Miller, J.E. Andrews: Holocene Variability In The Subpolar North Atlantic.
Abstract
Daley T.J., P.D.M. Hughes, F.A. Street Perrott, N.J. Loader, K.E. Barber: Evidence of the severity of the 8.2ka cold event from an ombrotrophic peat bog in Newfoundland.
Abstract
Holmes J. A., T. C. Atkinson, K. Barber, E. Fisher, P. Hopley, P. Hughes, N. Loader, J. Marshall, I. Robertson, P. Rowe, N. Scott, L. Sime, F.A. Street-Perrott, J. Tindall, P. Valdes, E. Wolff, T. Daley: Data - model comparison of precipitation isotope composition during rapid climate change events.
Abstract
LeGrande A. N., G. A. Schmidt, D. T. Shindell, C. V. Field, R. L. Miller, D. M. Koch, G. Faluvegi, G. Hoffmann: Consistent simulations of multiple proxy responses to an abrupt climate change event.
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Otto-Bliesner Bette L.: Freshwater in the North Atlantic and rapid climate change: modelling of the 8.2 ka and Heinrich events.
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Thomas E.R., E.W.W. Wolff, R. Mulvaney, J.P. Steffensen, S.J. Johnsen: High-resolution analysis of Dansgaard-Oeschger event 8 from the North Greenland Ice Core Project ice core.
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Wolff Eric W.: Rapid climate changes have occurred in the past: 8.2k and Dansgaard-Oeschger events in ice core and other palaeorecords.
Abstract
Illustrations
For a medium-size image with explanation, click on the thumbnails below. High resolution images suitable for printing are available by following the "High-res" link underneath this image. Please credit any images as indicated.
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Is the Atlantic overturning circulation slowing down?
Talks: Wednesday 25th, a.m. Posters: Wednesday 25th, p.m.
Since spring 2004 RAPID has been monitoring the North Atlantic Meridional Overturning Circulation (MOC) at 26.5°N and two years of continuous observations are now available. This is the first time that an ocean-wide observing system has been uses to measure the MOC. The overturning circulation is responsible for bringing heat northwards in the Atlantic and giving the UK and NW Europe a milder climate.
Analysis of the first year of data shows that the observing systems is working and able to measure the various components of the flow, using a combination of undersea cable measurements across the Florida Straits, satellite wind measurements, temperature and salinity measurements from the mooring array, and bottom pressure data also from the array. These and observations at other geographical locations in the North Atlantic suggest that changes are occurring in the MOC, but distinguishing whether these changes are due to variability or persistent trends requires a longer continuous observational record. Model results confirm the need for long-term continuous observations of the MOC if we are to be able to detect whether significant change is occurring.
Selected abstracts:
A. 25°N Observations
Bryden Harry L., Torsten O. Kanzow, Hannah R. Longworth, Stuart A. Cunningham, Molly O. Baringer, Lisa M. Beal, Joel J.- M Hirschi, William E. Johns, Christopher S. Meinen, Jochem Marotzke, Darren Rayner: Variability in the Atlantic meridional overturning circulation at 25°N.
Abstract
Kanzow T., S. Cunningham, H. Bryden, J. Hirschi, D. Rayner, J. Marotzke, W. Johns, M. Baringer, C. Meinen: Vertical compensation of mass transports associated with the meridional overturning circulation in the Subtropical North Atlantic.
Abstract
Rayner D., S. Cunningham, H Bryden, T. Kanzow, J. Hirschi, J. Marotzke, W. Johns, M. Baringer, C. Meinen, L. Beal : Evolution and maintenance of the transatlantic mooring array at 26.5°N.
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Longworth H. R., H. L. Bryden, M. O. Baringer: Variability in the Atlantic Meridional Overturning Circulation at 25°N from 1980 to 2005.
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Mujahid A., T. Kanzow, H.L. Bryden: Vertical Structure of the meridional flow field over the Western Boundary RAPID-MOC and MOCHA array.
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B. Other AMOC Observations
Schott, Friedrich: The Atlantic MOC during the past decade: a northern perspective.
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Lherminier, P., H. Mercier, C. Gourcuff, A.-M. Treguier, S. Bacon: MOC and water mass observations between Greenland and Portugal in Summers 1997, 2002 and 2004.
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Boscolo, R., R.R. Dickson: North Atlantic MOC Observations and Links to Arctic: From ASOF to iAOOS.
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McLeod, P., E.L. McDonagh, B.A. King, H.L. Bryden: The Atlantic Overturning Circulation at 36N.
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C. AMOC variability in climate models
Baehr, J., H. Haak, S. Alderson, S.A. Cunningham, J.H. Jungclaus, J. Marotzke: Timely detection of changes in the meridional overturning circulation at 26N in the Atlantic.
Abstract
Drijfhout, S. S., W. Hazeleger: Detecting Atlantic MOC changes in an ensemble of climate change simulations.
Abstract
Illustrations
For a medium-size image with explanation, click on the thumbnails below. High resolution images suitable for printing are available by following the "High-res" link underneath this image. Please credit any images as indicated.
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More photos from the 26°N array: Monitoring the MOC.
Will Greenland ice melt shut down the THC?
Talks: Thursday 26th, a.m. Posters: Thursday 26th, p.m.
One way to shut down the thermohaline circulation is to put large amounts of fresh water into the North Atlantic. One of the big unknowns in this system is the effect the melting of the Greenland ice sheet will have. A number of papers at the conference address this issue using a variety of models ranging from simple models to highly complex simulations.
Climate projections for the 21st century indicate a gradual decrease of the Atlantic MOC, which would be accelerated by an extra 5-12% by an input of melt-water (Jungclaus), although the circulation recovers in the 22nd century. Other model experiments show that a shut-down may occur for a worst-case scenario with strong increase in greenhouse gases, and a large freshwater input. (Kuhlbrodt, Swingedow). On land a shutdown will dampen the effect of global warming, and leads to an extra increase in sea level.
Developing models of the ice-sheet is necessary in order to predict the rate of ice melt and flow of fresh water into the North Atlantic. This task is adressed in the RAPID-project "Mass balance and freshwater contribution of the Greenland ice sheet: a combined modeling and observational approach", which presents early results at the conference (Ettema, Griggs).
Selected abstracts:
A. Understanding the effect of ice melt on the Atlantic MOC
Jungclaus, J.H., H. Haak, M. Esch, E. Roeckner, L. Mu, J. Marotzke: Will Greenland melting halt the Thermohaline Circulation?.
Abstract
Fichefet, T., E. Driesschaert, H. Goosse, P. Huybrechts, I. Janssens, A. Mouchet, G. Munhoven, V. Brovkin, S.L. Weber: Modeling the interactions between the Greenland ice sheet and climate during the next millennia.
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Kuhlbrodt, T.: The Atlantic meridional overturning circulation weakened by Greenland meltwater in global warming scenarios.
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Hosoe, T., J.M. Gregory: Exploration of multiple states of Greenland ice-sheet in a coupled AOIGCM.
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Swingedouw, D.M., P. Braconnot, P. Delecluse, E. Guilyardi, O. Marti: Mechanisms of AMOC Response to Changes in Surface Buoyancy Forcing under Global Warming in the IPSL-CM4 Model.
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B. Quantifying melt rate of the Greenland Ice sheet
Ettema, J., M. van den Broeke, E. van Meijgaard, J. Bamber, R. Gladstone, J. Griggs: Regional climate modelling of the Greenland ice sheet: preliminary results.
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Griggs, J.A., J.L. Bamber: Reducing uncertainty in contemporary freshwater flux from the Greenland ice sheet.
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Talks: Friday 27th, a.m. Posters: Thursday 26th, p.m.
The uncertainties in the climate system are considered in a number of papers that look at the risk of a shut down by the end of the century (Challenor, Rougier, Yohe). Such risk calculations are an important contribution to the debate about what is a 'dangerous' level of CO2 in the atmosphere.
If the THC does shut down we will need as much warning as possible before it happens. But, can we forecast the THC like we do the weather? A number of papers look at the predictability of the thermohaline circulation (Gamiz-Fortis, Spence). New high resolution climate models and comparisons between different models are helping to identify the key factors that affect the overturning circulation. In time this work will allow improved predictions to be made. In parallel, using simpler models and new statistical methods, work is in progress to quantify the risk and answer the question - "should we be worried about rapid climate change caused by sudden, unexpected changes in the North Atlantic circulation?"
Selected abstracts:
A. How good are our model predictions?
Spence, P., A. Weaver: The influence of mesoscale eddies and boundary currents on surface freshwater forcings used to drive MOC variations.
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Gamiz-Fortis, S.R., R. Sutton: Understanding the predictability of the MOC in a coupled climate model (HADCM3).
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B. Will slowdown of the MOC lead to high latitude cooling?
Jacob, Daniela: Impacts of changes in MOC on the European climate.
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Hazeleger, W., S. Drijfhout: Anthropogenic change in MOC and gyre-induced Atlantic Ocean heat transport.
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C. Estimating the probability of MOC shutdown
Challenor, P.G., D.P. McNeall: The Probability of Rapid Climate Change in an Intermediate Complexity Climate Model.
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McNeall, D.J., R.K.S. Hankin, P.G. Challenor: Tuning an intermediate complexity model to observations of the THC.
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Rougier, Jonathan C.: How can probability be used to quantify uncertainty in climate predictions?.
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Yohe, Gary, Michael Schlesinger, Richard Tol: Assessing the Risk of a Collapse of the Atlantic Thermohaline Circulation: The Effect of Different Base Cases.
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