The question is not whether the Greenland ice sheet will be around in 5,000 years, but 1,000 years. Now 1,000 years might, for some, seem lightyears away with respect to average human life expectancy (71.4 years by World Health Organisation data) but the very idea that the world’s leading polar scientists are asking the question is cause for concern alone.
The Greenland ice-sheet is one of the last remaining ice-sheets formed in the Miocene period around 200,000 years ago, due to the spread of icecaps and glaciers at the poles as well as seasonal addition of snow- and ice-layers. Covering 1.7m km2 across 1,000km at it’s widest and 2,400 at it’s longest, the Greenland ice-sheet is three times the size of Texas, and the UK could fit inside the area of the ice-sheet some 6.5 times, by square mile. In comparison to Antarctica, the Greenland ice sheet is a relatively recent development; some sections of Antarctica have been dated at some 45 million years old, as identified by extensive ice-core analysis.
Long term planetary glacial and interglacial periods are, by nature, cyclical, with ice ages coming and going over the last hundreds of thousands of years – as many climate change skeptics often note. Current observed long term trends however, show that global average warming is increasing at a rate never before seen, with strong emphasis on the anthropomorphic (human-forced) climate change impacts on the environment. During the last interglacial period – 100,000 years ago – Greenland was subject to temperatures 2-3ºc above current levels and, as a result, lost around 30% of its volume. This led to global average sea level rise of between 1.5-2m.
(Video credit: NASA’s Goddard Space Flight Center)
The trend of an increasing number of melt days in the annual cycle of the Greenland region is shown in the above video, taken from NASA’s Goddard Space Flight Center. Towards the late 1990s and into the early 2000s, the annual days of melt become more and more pronounced resulting in more water entering the ocean system from the ice sheet, affecting sea levels.
The Greenland ice sheet is no exception to global warming; it is shrinking at greater speed in not only the summer months but over autumn and winter as well – a trend observed since the 1970s. Recorded data on the polar region comes from two distinct sources; in-situ testing and remote sensing, via satellites.
Scientific research today often relies on remote sensing complemented by advanced climatological simulations and models, due to the costs involved in sending a team out to collect samples and carry out testing on the ice sheet. That said, some studies such as the ongoing multi-disciplinary Black and Bloom Project continue to ensure findings taken in-situ are being fed back into climatological simulations, increasing their effectiveness to project future developments and trends for the region.
Remote sensing of Earth’s many interlinked climate systems from space was ushered in during the 1970s with the LAGEOS (Laser Geodynamics Satellite or Laser Geometric Environmental Observation Survey) satellite among some of the first to be launched. Nowadays, the poles are monitored remotely by 5 satellites, from NASA’s GRACE to European Space Agency (ESA) Sentinel-2 and CRYOSAT-2 satellites. Remote sensing information, combined with costly in-situ testing, builds up an understanding of how the ice sheet and surrounding impermanent sea ice extent, thickness and composition is changing over time.
Dr Jack Landy, a lecturer and scientist at the Bristol University, has been studying the physical properties of Arctic sea ice through observation, monitoring and tracking over the last several years, as part of the Bristol University Glaciology Centre team. His research findings will be discussed in Part 2 of this three-part Arctic series, ‘Algal Blooms and Soot’.
With the long-term trends pointing to increased melting and loss of sea-ice and ice sheet in the region, this has a knock on effect to the Albedo effect. Snow reflects around 90% of the incoming solar radiation (insolation) from the atmosphere. If the snow starts to melt it loses some of its effectiveness in reflecting the insolation and this figure drops to around 60%. This means the remaining 30-40% will be absorbed by the icesheet, increasing warming and subsequent ice and snow melt. The difficulty with the Albedo effect is that, as more warming (and melting) occurs, the process begins to compound – more ice melts and feeds back into the global system, raising sea levels.
Once the Albedo effect snowball starts rolling, it becomes next to impossible to reverse the process without major intervention – the Paris Climate Agreement is a start, but a lot more needs to be done on local, national and international level. In the meantime the 1,000 year question mark still stands.
To learn more about the Greenland ice sheet and Arctic region, sign up to the ESA’s free FutureLearn course here – available until the 23rd August 2017.