As the 2013 year draws to a close, I thought it would be great to highlight some of our most important science discoveries in Antarctic Glaciology. Enjoy!
The IPCC 5th Assessment Report
The 5th Assessment Report of the IPCC began with the publication of the Summary for Policy Makers in November 2013. The IPCC found that,
Warming of the climate system is unequivocal, and since the 1950s, many of the changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.
With regards to the Cryosphere, the IPCC found:
Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide.
The IPCC stated that the average rate of ice loss from the Antarctic ice sheet has likely increased from 30 [–37 to 97] gigatonnes per year over the period 1992–2001 to 147 [72 to 221] gigatonnes per year over the period 2002 to 2011. There is very high confidence that these losses are mainly from the northern Antarctic Peninsula and the Amundsen Sea sector of West Antarctica.
It is very likely that the annual mean Antarctic sea ice extent increased at a rate in the range of 1.2 to 1.8% per decade (range of 0.13 to 0.20 million km2 per decade) between 1979 and 2012. There is high confidence that there are strong regional differences in this annual rate, with extent increasing in some regions and decreasing in others.
The RAISED Consortium
2013 was the year for major international collaborations. In 2013, the RAISED* Consortium (*Reconstruction of Antarctic Ice Sheet Deglaciation) divided the Antarctic Ice Sheet into six sectors, and a group of community-wide glaciologists attempted to provide comprehensive reviews of each of these six sectors. These reviews are progressively being published in Quaternary Science Reviews, and it is hoped that these papers will spur greater efforts to constrain past ice sheet extent, thickness and rates of ice-sheet change. Papers already published online from this special issue include:
- East Antarctic Ice Sheet
- Weddell Sea sector
- Ross Sea sector
- Amundsen Sea and Bellingshausen Sea sector
Key science papers of 2013
The papers below are some of the recent publications that I find most interesting with respect to Antarctic glaciology.
Sea levels will rise by 2.3 m per 1°C of warming within the next 2000 years
A new paper published by Levermann et al. in PNAS demonstrated that global warming will result in at least 2.3 m of sea level rise per one degree of warming within 2000 years. This sea level rise will be derived from thermal expansion of the ocean, glacier melt and ice sheet melt.
Snowmelt is increasing on the Antarctic Peninsula
A paper by Nerile Abram and co-workers in Nature Geoscience used an ice core from James Ross Island to reconstruct snowmelt over the last 1000 years. They showed that snowmelt increased dramatically over the Twentieth Century.
This contrasts with ice-core records from Ellsworthland, where although warming has been observed since the 1950s, the rate of warming is within the bounds of natural variability (Thomas et al.).
New numerical models of the Antarctic Ice Sheet
2013 was marked by several advances in numerical ice sheet modelling. Golledge et al. produced the best-yet numerical model of the entire Antarctic Ice Sheet, with an assessment as to its fit to the geological data.
As well as advances in understanding past ice sheet dynamics, a number of papers considered the future response of Antarctic glaciers to climate change. Winklemann et al. proposed that increased snowfall would lead to increased ice discharge around Antarctica, offsetting potential future gains in ice mass. Meanwhile,Barrand et al. argued that snowfall will increase ice mass on the Antarctic Peninsula, but this will be countered by grounding line recession following ice-shelf collapse.
Ice flow in the Weddell Sea is complex
The grounding line in the Weddell Sea at the Last Glacial Maximum remains a source of contention, but new evidence of ice streaming in the Ronne and Filchner Troughs is emerging (Hillenbrand et al., 2013).
New evidence from radio echo-sounding of the internal layers of the Weddell Sea sector of the ice sheet indicates that this area underwent reorganisation during the Holocene, suggesting that the area may be able to undergo rapid change (Siegert et al. 2013).
Pine Island Glacier continues to recede
The PIG remains a hot source for scientific research. Sergienko et al. found rib-like patterns of very high basal shear stress beneath Pine Island Glacier and Thwaites Glacier. Subglacial meltwater may control the evolution of these high-stress ribs, which may cause changes in grounding-line location.
Pine Island Glacier continues to retreat, and thinning of the terminus continues to accelerate (Park et al.).
Ice shelf complexities
Ice-shelf dynamics become ever more complex. A new paper by Anne Le Brocq showed that meltwater plumes melt giant canals beneath ice shelves. Features on the ice surface correspond with the location of the canals.
Add your own science highlights
What do you think the key science highlights in Antarctic climate and glaciology are? Use the comments box to add what you think the most important findings of 2013 were.