Is Climate Change Slowing Down the Ocean? | Susan Lozier | TED

Adelard of Bath and Modern Oceanography

Introduction to Adelard of Bath

• The speaker introduces Adelard of Bath, a 12th-century natural philosopher who compiled a list of unanswered questions about nature.

• Among his 76 questions, topics relevant to oceanography include the salinity of sea water and the reasons behind tidal movements.

Evolution of Oceanographic Questions

• Nine centuries later, contemporary oceanographers are exploring complex issues such as changes in navigation routes due to melting ice and the health of marine ecosystems in warming waters.

• A critical question raised is whether climate change will lead to the collapse of ocean overturning circulation.

Understanding Ocean Overturning Circulation

• The speaker explains that ocean waters are in constant motion, with surface currents and large-scale currents connecting different ocean basins.

• The "ocean overturning circulation" begins at high latitudes where cold winds convert warm surface waters into denser cold waters that sink.

Importance of Ocean Overturning

• This process redistributes heat globally, maintaining a significant temperature difference between the equator and poles; without it, polar regions would freeze while tropics would become excessively hot.

• Additionally, sinking waters carry carbon dioxide from the atmosphere into the ocean, which has increased alongside rising atmospheric CO2 levels since the Industrial Revolution.

Impacts on Marine Ecosystems

• While this carbon uptake reduces atmospheric CO2 levels—a positive outcome—it also increases ocean acidity, negatively affecting marine species that rely on calcium carbonate for shells and skeletons.

Consequences of Warming Oceans

• As oceans warm and ice melts, surface waters may not become dense enough to sink during winter months, potentially slowing down overturning circulation.

• A slowdown could lead to reduced carbon uptake by oceans and significant disruptions in climate patterns including stronger hurricanes and intense precipitation events.

Potential for Abrupt Changes

• Historically viewed as slow processes over thousands of years, studies suggest that changes in overturning can occur rapidly within decades or even years due to human-induced warming.

Current Projections for Overturning Circulation

• Advances in climate modeling have improved understanding regarding risks associated with potential abrupt collapses in overturning circulation.

Future Outlook

• Current models indicate that while an outright collapse before 2100 is unlikely, weakening by 11% to 34% is expected this century—enough to cause significant climatic disruptions.

Importance of Observations

• Continuous measurements are crucial for refining predictions; historical data collection began only recently when resources became available.

International Observational Efforts

Oceanographic Research and Climate Change

Overview of OSNAP and Ocean Measurements

• The OSNAP (Overturning in the Subpolar North Atlantic Program) involves deploying instruments on moorings to measure ocean currents, temperature, and salinity. Research vessels have been tracing the OSNAP line since 2014.

• Oceanographers from various countries participate in these research cruises, utilizing advanced technology such as a rosette of bottles for deep ocean water sampling.

• An autonomous glider is employed to take measurements at depth, surfacing periodically to transmit data via satellite. This innovation allows researchers to collect data without being physically present at sea.

Challenges and Insights from Data Collection

• While conditions during research cruises can be challenging, the scenic views often make the experience worthwhile for scientists involved.

• Current OSNAP data does not indicate whether ocean overturning is increasing or decreasing due to inherent noise in both market trends and oceanic conditions. Long-term confidence suggests that warming climate will lead to a decline in overturning.

Interconnectedness of Ocean Systems

• The ocean's interconnected nature means that changes in one area affect others; thus, understanding global measurements is crucial for accurate assessments of overturning dynamics.

• A NOAA buoy measures carbon exchange between the ocean and atmosphere as part of a larger global measurement system involving ships, moorings, and buoys across oceans—forming the backbone of 21st-century oceanography.

Addressing Climate Issues