In January 2014 new research revealed that Pine Island Glacier in Antarctica was much more susceptible to climate change and ocean variability than previously thought
Island Glacier as the most rapidly shrinking glacier on the planet and have suggested that it is contributing to sea level rise faster than any other glacier on the planet.
About Pine Island
Glaciers and sea level change
A rift in the ice
Researching Pine Island Glacier
Over thousands of years snow has fallen across Antarctica and been compressed into ice, forming massive ice sheets. These ice sheets flow as glaciers down hill from the Antarctic Plateau and its mountain ranges, towards the coast. You can see a visualisation of how ice moves across Antarctica here.
When the ice reaches the sea, it floats and so forms an ice shelf. When parts of the ice shelf weaken they break off as icebergs and drift out to sea where they will eventually melt.
Pine Island Glacier is one of the two largest ice streams draining the West Antarctic Ice sheet (the other is Thwaites glacier). Pine Island Glacier is 140km long of which around half covers the land as an ice sheet, while the other 70km extends out over the sea floating as an ice shelf. The glacier flows into Pine Island Bay leading to the Amundsen Sea.
Facts about Pine Island Glacier
It drains an area equivalent to two thirds the size of the United Kingdom
It is the most rapidly shrinking glacier on the planet and is contributing more to sea level rise than any other ice stream
It is approximately 2km thick, but is thinning by more than 1 metre per year
There is a subglacial volcano underneath Pine Island Glacier which erupted around 2000 years ago
At present Pine Island Glacier is an intensively studied area of Antarctica because it accounts for around 10% of all the ice on the West Antarctic ice sheet and so has the potential to make a significant contribution to sea level rise.
Ice sheets are relevant to climate change research as they can affect sea level. If an ice sheet shrinks it will contribute to sea level rise as less water is trapped as ice in the ice sheet. Past records suggest that shrinkage of ice sheets happens at a faster rate than ice sheet growth.
Satellite observations have revealed that in West Antarctica the ice is thinning, the flow rate is increasing, and the point where the floating ice shelf meets the grounded ice (the grounding line) is retreating inland. In recent years, the glacier has thinned at a rate of around 1m per year and this has major implications for sea level rise which could potentially be 3.5-10mm over the next 20 years. If the entire West Antarctic ice sheet were to melt global sea level would rise by around 5 metres.
In addition to the thinning of the glacier, in October 2011 a large crack was observed in the ice (see photo) and this was the first sign that the glacier was likely to calve an iceberg into the Amundsen sea.
An aerial view of the crack in the Ice on Pine Island Glacier October 2011. Source: Flickr user NASA ICE
The crack gradually became wider until an iceberg was formed in November 2013. The iceberg was around 720 square kilometres in size which is roughly eight times the size of Manhattan Island in New York. Large icebergs like this has broken from the glacier before, the last time was in 2007.
Iceberg breaks away from the ice shelf on Pine Island Glacier November 2013. Source: NASA
Both satellite and radar measurements have recorded thinning of the glacier as well a surge in velocity of the Pine Island Glacier in recent decades. The glacier has thinned during the past few decades, experienced an acceleration in its flow and a recession of the grounding line (see diagram below)
The acceleration is thought to have been caused by the thinning of the ice shelf. Scientists are still researching why the glacier is accelerating. One theory is that warmer temperatures are being experienced in the water around Antarctica. The warmer water then melts the ice on the underside of the ice shelf which weakens the structure and makes it easier for icebergs to calve.
Changes to Pine Island Glacier. Source: Antarctic Glaciers
A study published in the journal Science suggests that the Pine Island Glacier is much more susceptible to climate and ocean variability than initially thought. The research team discovered large fluctuations in ocean heat in Pine Island Bay. They also discovered that oceanic melting of the ice shelf decreased by around 50% between 2010 and 2012, and this was possibly due to a La Niña event in the Pacific Ocean which could have led to a cooling of the water around the glacier. Because melting glaciers contribute to sea level rise it is important that the processes which are driving the thinning of the ice shelf are understood.
"Beneath the shelf, ocean waters are just above 1°C, nearly 3°C warmer than elsewhere along the Antarctic coast. Because of this, the floating portion of Pine Island Glacier is melting more than one hundred times faster than most other ice shelves. The typical rate of ice shelf melt is around 10cm per year, but Pine Island Glacier ice shelf is melting at 10m per year. If the temperature of seawater beneath it were to rise by 1°C, the rate of melting would double. This would lead to substantial thinning of the floating ice and eventually of the glacier inland. To understand whether such a change could be driving the thinning, we must understand what controls the water temperature beneath the sheet." (NERC)
The Natural Environment Research Council (NERC) is currently funding a series of research projects to explore what is happening on Pine Island Glacier: iSTAR (Investigating the stability of the West Antarctic ice sheet. These projects that are part of iSTAR involve the collaboration of many research institutions to investigate what is happening in the Amundsen Sea next to the ice sheet, and what is happening to the ice sheet itself.
They have four main projects:
Ocean2ice (iSTAR A): this project investigates how warmer water gets close to the ice
Ocean under ice (iSTAR B): this project investigate what might cause ocean temperature to change and how this is likely to affect the rate of melting on the ice
Dynamic ice (iSTAR C): this project seeks to understand the processes involve in the thinning of the ice shelf
Ice loss (iSTAR D): this project aims to collect data from on the ground to complement the satellite measurements in order to form a comprehensive picture of ice loss on the West Antarctic Ice sheet and to determine the past and present contribution to seal level.
Doing research on the ground in Pine Island is extremely challenging. The ice shelves are heavily crevassed which means that it is not possible to land in the area by aeroplane. Satellite observations have been extremely valuable in identifying changes that have happened in Antarctica; however they can’t reveal what is happening beneath the ice.
Researchers are using a variety of methods to investigate changes in Antarctica.
Satellites are used to take high resolution images. As the satellite orbits it can repeatedly take images which when used altogether can be used to monitor change
Seismic surveys which involves creating a shockwave which travels through the ice and is reflected back from the floor of the glacier. The reflections are recorded by sensors called geophones
Ice cores are extracted in order to investigate past climate variability. By measuring isotopes in different layers of ice from an ice core scientists can create a past climate record for the area
Radar surveys where radar pulses are fired through the ice sheet and returning echoes are recorded so the scientists can measure the thickness of the ice. It was using radars to map the bedrock that scientists discovered a sub-glacial volcano by the Hudson Mountains (which is close to Pine Island Glacier) that last erupted around 2000 years ago
Autosub, an underwater vehicle that allows scientists to access the ocean beneath the ice shelve so they can take various measurements including: water temperature, salinity, depth of sea floor, water currents.
In 2013 scientists began using another method to monitor changes on Pine Island Glacier. The Aircraft Deployable Ice Observation system sensors look a bit like javelins. They are released through a tube from an aircraft and stick into the ice. They are equipped with GPS so the scientists can track Pine Island Glacier’s movements. Pine Island is extremely remote so this is now allowing areas that were out of reach to be researched.
Twenty-five of these ‘javelins’ have been successfully installed in Pine Island Glacier (of 33 that were deployed). They are equipped with GPS in order for scientists from the BAS to track any movement towards the sea. These have been deployed as much of the area on Pine Island Glacier is inaccessible as it is heavily crevassed. Released from a tube on an aircraft the ‘javelins’ hit the ice at around 50m per second with small brakes that are fitted to the side to prevent them going too deep into the ice. They are expected to last for about 2 years. The data provided from these javelins will allow scientists to develop numerical models that will hopefully be able to model scenarios for changes to Pine Island Glacier over the next few decades.
Given Pine Islands sensitivity to climate change and the potential impact it could have on global sea levels it is important that we understand the changes that are occurring in Antarctica. You can follow the progress of the researchers working on Pine Island and other areas in Antarctica via the iSTAR website.
‘Antarctic ice volume measured’ BBC News 08 March 2014
British Antarctic Survey
'iSTAR Fact file Pine Island Glacier'
‘Major Iceberg Cracks off Pine Island Glacier’ NASA 15 November 2013
‘Pine Island Glacier Melting Past the Point of No Return’ Independent 14 January 2014
‘Pine Island Glacier’s retreat ‘irreversible’’ BBC News 14 January 2014
‘Pine Island Glacier produces giant iceberg’ BBC News 10 July 2013
‘Pine Island Glacier sensitive to climate variability’ British Antarctic Survey 02 January 2014
‘Science ‘javelins’ spear Pine Island Glacier BBC News 19 April 2013
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