Video presented by Shad O'Neel, PhD, Scripps Institution of Oceanography, as part of the 2008 series &quot;Perspectives on Ocean Science.&quot; Dr. O'Neel provides a tour of coastal glaciers and explains why scientists believe these glaciers' unique behavior will make them one of the largest contributors to sea level rise in the next century. [56:45 min]
The melting Laurentide Ice Sheet discharged thousands of cubic kilometres of fresh water each year into surrounding oceans, at times suppressing the Atlantic meridional overturning circulation and triggering abrupt climate change. Understanding the physical mechanisms leading to events such as the Younger Dryas cold interval requires identification of the paths and timing of the freshwater discharges. Although Broecker et al. hypothesized in 1989 that an outburst from glacial Lake Agassiz triggered the Younger Dryas, specific evidence has so far proved elusive, leading Broecker to conclude in 2006 that "our inability to identify the path taken by the flood is disconcerting". Here we identify the missing flood path-evident from gravels and a regional erosion surface-running through the Mackenzie River system in the Canadian Arctic Coastal Plain. Our modelling of the isostatically adjusted surface in the upstream Fort McMurray region, and a slight revision of the ice margin at this time, allows Lake Agassiz to spill into the Mackenzie drainage basin. From optically stimulated luminescence dating we have determined the approximate age of this Mackenzie River flood into the Arctic Ocean to be shortly after 13,000 years ago, near the start of the Younger Dryas. We attribute to this flood a boulder terrace near Fort McMurray with calibrated radiocarbon dates of over 11,500 years ago. A large flood into the Arctic Ocean at the start of the Younger Dryas leads us to reject the widespread view that Agassiz overflow at this time was solely eastward into the North Atlantic Ocean.
Sea level rise is one of the major long-term consequences of human-induced climate change. Future projections of sea level changes and their regional expression are of crucial importance for the sustainability of coastal settlements around the world. The Fourth Assessment Report of IPCC (AR4) had comprehensively assessed key processes contributing to
past, present and future sea level changes. However, process understanding was limited and thus both size and uncertainties associated with some of these contributions remained still largely unknown. This also hampered the overall projections of global mean sea level rise in AR4. The future dynamical behaviour of the large polar ice sheets of Antarctica and Greenland in a changing climate was identified as the primary origin of the large uncertainty in the AR4
projections of sea level rise for the 21st century.
IPCC Working Group I (WGI) has acknowledged the relevance of this specific topic and thus (1) proposed a chapter on 'Sea Level Change' in its contribution to the IPCC Fifth Assessment Report (AR5) and (2) organized a targeted IPCC Workshop on 'Sea Level Rise and Ice Sheet Instabilities' very early in the assessment cycle for the IPCC's AR5. This
Workshop took place in Kuala Lumpur, Malaysia, from 21 to 24 June, 2010. The Workshop brought together experts from very diverse disciplines with a wide range of expertise, covering oceanography, ice sheet dynamics, glacier research and hydrology to discuss latest results from both observations and modelling relevant for sea level change. The workshop structure included a combination of plenary sessions with invited keynote presentations, group discussions, poster sessions and, finally, topical breakout groups.
This Workshop Report contains a concise summary of the overall discussions and conclusions of the Workshop as well as summaries of the discussions in the breakout groups. It further includes the extended abstracts of the keynote presentations and poster abstracts presented during the Workshop.