The Great Ocean Conveyor: Discovering the Trigger for Abrupt Climate Change by Wallace BroeckerPublisher's website | Google Books version of this book | see this book at Amazon
Book Club goals
- Facilitate a discussion of the role of thermohaline circulation in climate change
- Share ideas of how concepts from this book can translate into our own courses
Duration - 1 hour.
Format - Online discussion via phone and Elluminate web software on the book described below.
Registration - There is no registration fee, but registration is required to save a space (and because space is limited to 10, be sure you can commit before registering). Registration closes when the spaces fill or one week before each event, whichever comes first.
Contact - For questions contact Karin Kirk or Katryn Wiese (kkirk at carleton.edu or katryn.wiese at mail.ccsf.edu).
During our 1-hour book club discussion we will share thoughts from the book and discuss how material or ideas from this book could be useful for teaching in an undergraduate setting. Prior to the book club discussion, participants will be encouraged to share their impressions of the book via a threaded discussion.
"Wally Broecker is one of the world's leading authorities on abrupt global climate change. More than two decades ago, he discovered the link between ocean circulation and climate change, in particular how shutdowns of the Great Ocean Conveyor--the vast network of currents that circulate water, heat, and nutrients around the globe--triggered past ice ages. Today, he is among the researchers exploring how our planet's climate system can abruptly "flip-flop" from one state to another, and who are weighing the implications for the future. In The Great Ocean Conveyor, Broecker introduces readers to the science of abrupt climate change while providing a vivid, firsthand account of the field's history and development." "Could global warming cause the conveyor to shut down again, prompting another flip-flop in climate? What were the repercussions of past climate shifts? How do we know such shifts occurred? Broecker shows how Earth scientists study ancient ice cores and marine sediments to probe Earth's distant past, and how they blend scientific detective work with the latest technological advances to try to predict the future. He traces how the science has evolved over the years, from the blind alleys and wrong turns to the controversies and breathtaking discoveries. Broecker describes the men and women behind the science, and reveals how his own thinking about abrupt climate change has itself flip-flopped as new evidence has emerged.""Rich with personal stories and insights, The Great Ocean Conveyor opens a tantalizing window onto how Earth science is practiced."From the Princeton University Press website
"Wally Broecker is the Newberry Professor of Earth and Environmental Sciences at Columbia University. His books include Fixing Climate: What Past Climate Changes Reveal about the Current Threat--and How to Counter It and Chemical Oceanography. He is a member of the National Academy of Sciences."
Summary from Book Club Discussion - Feb 11, 2011
- Most participants do teach with the principle of the thermohaline "conveyor belt" circulation, but those who teach oceanography courses find that the simplified diagram is too generalized and does not accurately portray the importance of surface currents and the linkages between surface currents and deep water currents.
- The book was complex and we did not come away with strong conclusions about the precise causes, effects and drivers of thermohaline circulation's role in abrupt climate change. For example, if glacial Lake Agassiz drained north via the Arctic Ocean, is that still thought to have provided sufficient meltwater to prevent deepwater formation?
- There was general agreement that the most useful application of this book for teaching was its portrayal of the process of science and how the path to scientific understanding is non-linear and comes only after examining and re-examining many lines of data. Similarly, the book illustrated the importance of collaborations between many types of scientists, over the course of many years, to bring new paradigms to light. (See related SERC web resource, Teaching the Process of Science.)
- A key question we had after completing the book was the potential impact of future slowdowns of the thermohaline circulation on our climate. To what degree is the warming Arctic likely to produce a pool of meltwater that prevents the sinking of new deep water in the North Atlantic? Are there means to measure or predict deep ocean temperature or CO2 concentration? What do the latest research, modeling and measurements tell us about the likelihood of a slowdown of thermohaline circulation? It's still not clear what triggers abrupt changes and what would global warming do.
- Some monitoring is being done via Argo, which is a global array of 3,000 free-drifting profiling floats that measures the temperature and salinity of the upper 2000 m of the ocean. This allows, for the first time, continuous monitoring of the temperature, salinity, and velocity of the upper ocean, with all data being relayed and made publicly available within hours after collection.
- A June 2010 Science abstract, Deconstructing the Conveyor Belt presents an alternate view of ocean circulation by examining how the ocean's eddy and wind fields play a role in the ocean's overturning.
- Peter Mahaffy shared a link to a collection of interactive, web-based educational resources he and others are working on for the International Year of Chemistry. Explaining Climate Change
Activities and materials for teaching about paleoclimate and abrupt climate change
Cool Cores Capture Climate Change- This is an in-depth module that uses specialized software, Paleontological Stratigraphic Interval Construction and Analysis Tool (PSICAT), to create graphic models of sediment cores based on data provided by ANDRILL scientists to demonstrate evidence of climate change over Earth's Geologic Time.
Climate History from Deep Sea Sediments - This module focuses on reconstructing the Paleocene-Eocene Thermal Maximum (PETM), which occurred between 50 to 60 million years ago. Users access Integrated Ocean Drilling Program (IODP) core data with Virtual Ocean software. They identify appropriate bathymetric depths for finding desired marine sediments. Then, they locate potential core, log, and seismic data to map the marine sediment biostratigraphy. Last, users download and examine ocean floor core data from the CHRONOS data portal to search for a specific planktonic foraminifera, Acarinina praepentacamerata, that prefers near-surface (warmer) ocean conditions.
Modeling the oceanic thermohaline circulation with STELLA - This activity describes the construction of and then experimentation with a STELLA model of the thermohaline circulation in the north Atlantic. Based on a famous paper by Stommel (1961), this model exhibits two stable states or attractors. The dynamics of this system are relevant to understanding episodes of abrupt climate change such as the Younger Dryas.
Gulf Stream Heat Budget and Europe's Mild Climate: A Problem-based Learning Activity - Students are presented with a scenario to recommend whether the Gulf Stream is responsible for keeping Europe warm and the potential effects if polar ice were to continue melting.
Rayleigh Fractionation Visualization - An Excel spreadsheet gives an account of Rayleigh fractionation, the progressive removal of the heavier oxygen isotope as a moist air parcel moves from the subtropics to the high latitudes. This exercise is useful for the interpretation of ice core paleoclimate records.
Sediments and the Global Carbon Cycle - This is a series of exercises designed to introduce undergraduate students to the role of sediments and sedimentary rocks in the global carbon cycle and the use of stable carbon isotopes to reconstruct ancient sedimentary environments. Students will make some simple calculations, think about the implications of their results, and see an optional demonstration of the density separation of a sediment sample into a light, organic fraction and a heavier mineral fraction.
Using Real Data from Ices Cores and Salt Cores to Interpret Paleoclimate - Students use four paleoclimate curves from the past 150,000 yrs to make interpretations about temporal and spatial aspects of paleoclimate and to use that data to make predictions about future global climate trends.
Ice Core Exercise - This assignment (for upper-division/graduate students) provides exposure to ice core data, problem-solving to register data sets, technical challenges in data manipulation and statistics, and an opportunity to synthesize across time and space.
Vostok Ice Core Activity - Students use Excel to graph and analyze Vostok ice core data. Data includes ice age, ice depth, carbon dioxide, methane, dust, and deuterium isotope relative abundance
Fathoms, Ship Logs, and the Atlantic Oceanand Introduction to the structure of the ocean using CTD data - These are high school level activities for teaching physical oceanography
Activity IdeasSubmitted at the 2008 Cutting Edge workshop on teaching climate change using ice core data. These ideas are not fully-formed teaching activities but rather they are outlines that could be developed into fully formed activities.
Bipolar Climate Puzzler - This is an outline for a paleoclimate activity that have students develop graphs of data from the GISP and Vostok core data, then compare long-term scale (multiple glacial cycles) and short-term scale (9,000 - 15,000 year time period) data from Greenland vs Antarctica.
Bring it Home: Evidence for Abrupt Climate Change - This is an idea for an activity that uses pollen data and ice core date to compare the timing of major temperature change with pollen record and examine abrupt changes in plant communities.
Climate change and interpreting ice core data - Designed for an upper-level course, this activity idea involves both individual and group work to interpret and compare graphs for CO2, volcanic, and solar forcings over the past 1000 years and temperature records over the past 2000 years.
How do polar and tropical ice cores correlate? - Designed for an upper-level course, this activity idea involves students downloading and evaluating data from specified ice cores in Greenland and Bolivia in an attempt to recognize and interpret rapid climate change events.
Exploring Paleoclimatology in the Classroom Using Coral Radioisotope Data from Rarotonga Island in the South Pacific
Exploring Paleoclimatology in the Classroom using Vostok Ice Core Data
Ocean-Atmosphere Circulation - This collection includes visualizations about sea surface temperature (SST), currents, El Nino-Southern Oscillation (ENSO), and Pacific Decadal Oscillation (PDO)
Paleoclimate - This collection features visualizations of Earth's climate through geologic time, including visualizations of climate forcings such as Milankovitch Cycles.
Other Teaching Materials
Paleoclimatology: How Can We Infer Past Climates? - A primer on how researchers use climate proxies to infer past climate and a list related links for more information.
Stable Isotope Primer and Some Common Uses in Hydrology - This page offers a primer on stable isotopes, including what they are and how they can be used in hydrology; it also provides links to related resources.