Dr. James Hansen (Director of Climate Science, Awareness and Solutions Program Earth Institute, Columbia University) and 18 co-authors just published an article – Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous – in the journal Atmospheric Chemistry & Physics. Their article is significant because not only does it raise the issues of superstorms and sea level rise that are associated with human forcing of climate change, but their research also suggests that current climate models do not adequately gauge the effects of ice melt runoff from the Antarctic and Greenland ice sheets. The video embeded below is done by Dr. Hansen and his co-authors and is a good abstract of their recent research findings.
Jakobshavn Isbræ, Greenland’s fastest flowing glacier, has been moving even faster over the past several years. The Jakobshavn Glacier, or Jakobshavn Isbræ, is located on the west coast of Greenland and drains a major part of the Greenland ice sheet into a deep ocean fjord. Accordingly, the Jakobshavn Glacier could add significantly to sea level rise.
Recorded speeds of glacial flow during the summer of 2012 topped out at more than 17 kilometers per year, or over 46 meters per day. In fact, the transient summer speeds observed for 2012 probably represent the fastest observed speeds for any outlet glacier or ice stream in Greenland or Antarctica. In a paper published recently in The Cryosphere, Joughin and others, note that:
We have extended the record of flow speed on Jakobshavn Isbræ through the summer of 2013. These new data reveal large seasonal speedups, 30 to 50% greater than previous summers. At a point a few kilometres inland from the terminus, the mean annual speed for 2012 is nearly three times as great as that in the mid-1990s, while the peak summer speeds are more than a factor of four greater. These speeds were achieved as the glacier terminus appears to have retreated to the bottom of an over-deepened basin with a depth of 1300m below sea level. The terminus is likely to reach the deepest section of the trough within a few decades, after which it could rapidly retreat to the shallower regions 50 km farther upstream, potentially by the end of this century.
The warming trend in the Arctic correlates with Greenland’s glaciers thinning and retreating progressively inland. The rapid retreat of the Jakobshavn Isbræ, however, is due not only to the warming trend, but to a number of feedbacks. The primary control on the glacial flow now is the physical location of the glacier’s calving front. The calving front is currently located in a deep area of its outlet fiord, an area where the underlying rock bed is about 1300 meters below sea level. As the glacier loses ice in this area – basically the ice in front that is holding back the flow – the flow speeds up.
The contribution to sea level rise from the Jakobshavn Isbræ may be significant. One of the study’s authors, Ian Joughlin, is quoted in Science Daily, 2/3/2014, as saying:
We know that from 2000 to 2010 this glacier alone increased sea level by about 1 mm. With the additional speed it likely will contribute a bit more than this over the next decade.
So what should we expect for the Jakobshavn Isbræ’s future? Joughlin and others summarized this by:
Thus, the potential for large losses from Greenland is likely to be determined by the depth and inland extent of the troughs through which its outlet glaciers drain. These features are only beginning to be well resolved by international efforts such as NASA’s Operation IceBridge. The relatively sparse data collected thus far indicate that, with its great depths and inland extent, Jakobshavn’s Isbræ is somewhat unique (Bamber et al., 2013), suggesting that it may be difficult for the majority of Greenland’s outlet glaciers to produce or to sustain such large increases in ice discharge.
Of interest may be an earlier Geopostings on “Chasing Ice” that showed a 2012 huge calving event from the Jakobshavn Isbræ.
New sets of interactive maps help to visualize both the impact of rising seas on the world’s coastlines and U.S household carbon footprints.National Geographic has posted a set of world-wide interactive maps that show new coastal outlines resulting from the premise of all ice melting and thus raising sea level approximately 216 feet. As noted by the authors:
There are more than five million cubic miles of ice on Earth, and some scientists say it would take more than 5,000 years to melt it all. If we continue adding carbon to the atmosphere, we’ll very likely create an ice-free planet, with an average temperature of perhaps 80 degrees Fahrenheit instead of the current 58.
Continuing on the topic of adding carbon to the atmosphere, University of Berkeley researchers, Christopher Jones and Daniel Kammen, looked at the spatial distribution of U.S. household carbon footprints. The researchers first point out the obvious in that carbon footprints in densely populated areas are typically low because of smaller residences, shorter commutes, and the availability of mass transit. Here’s the catch though – the suburbs have an unusually large carbon footprint and are always in serious need of carbon management. In fact, the footprint is so large that it negates the “green” urban core. As Jones and Kammen summarize:
As a policy measure to reduce GHG emissions, increasing population density appears to have severe limitations and unexpected trade-offs. In suburbs, we find more population- dense suburbs actually have noticeably higher HCF, largely because of income effects. Population density does correlate with lower HCF when controlling for income and household size; however, in practice population density measures may have little control over income of residents. Increasing rents would also likely further contribute to pressures to suburbanize the suburbs, leading to a possible net increase in emissions. As a policy measure for urban cores, any such strategy should consider the larger impact on surrounding areas, not just the residents of population dense communities themselves. The relationship is also log?linear, with a 10-fold increase in population density yielding only a 25% decrease in HCF. Generally, we find no evidence for net GHG benefits of population density in urban cores or suburbs when considering effects on entire metropolitan areas.