Warm ocean water melting Antarctica from below adding to sea level rise

Latest observational data from Amundsen Sea embayment (ASE) of West Antarctica confirms the retreat of ice shelf grounding lines caused by warmer water melting the underside of the ice shelves.

Warm ocean waters are melting the junction of the ice shelves where they meet the bedrock, so that the grounding line retreats. This then allows for an acceleration in glacier dischange of ice mass to the sea increasing sea level rise.

Many of the glaciers of the West Antarctic Ice Sheet (WAIS) have topographies where they get deeper as they go further inland.

As the ice shelf grounding line retreats into deeper areas due to basal melting by warmer water, it moves much more rapidly, which then allows more warm water to continue the process of basal melting, and so the ice mass discharge from the glaciers speeds up.

Volcanic activity adds further to instability of West Antarctic Ice Sheet

Volcanic activity detected near the Executive Committee range in Marie Byrd Land in West Antarctica adds another factor to the instability of the West Antarctic Ice Sheet (WAIS). A small eruption under the ice could result in melt water adding substantial lubrication to the bottom of a portion of the ice sheet, speeding up the ice stream discharge into the Ross Sea.

The West Antarctic Ice sheet is buttressed by huge ice shelves at it's edges which hold back the ice streams. Warming Southern ocean currents are melting ice shelves, causing them to retreat, allowing faster discharge of ice flows from the interior. Much of the ice sheet is grounded on a sub-glacial basin below sea level, so as the ice shelf grounding line retreats, more warm water can interact with the ice to speed the discharge and collapse of the ice sheet. Volcanic activity adds further potential instability to this process.

West Antarctic Ice Cores find changes at upper bound of normal

A new ice core study from the West Antarctic Ice Sheet (WAIS) concludes that current dramatic and unusual warming changes on the West Antarctic Ice Sheet may still be in the bounds of natural decadal variability.

In other words, the warming trend signal is still not strong enough to distinguish it above the noise of peak warming periods in multi-decade long cycles involving the Tropical Pacific atmospheric circulation, sea surface temperatures and the El Niño (ENSO) cycle.

While acknowledging the rapid warming over the West Antarctic Ice Sheet the authors conclude that "It is unknown whether these changes are part of a longer-term trend."

Related: Global warming in Antarctica: Thwaites and Pine Island Glaciers | Waking the giant: Global Warming in the Weddell Sea | Southern Ocean warming impact on Antarctic Ice Sheet and global sea level | Antarctic Paradox: ocean warming melting ice shelves causing sea ice expansion

Antarctic Octopus genetics reveals past West Antarctic Ice sheet collapse

It seems the genetics of the Antarctic Octopus is showing us how fragile the West Antarctic Ice sheet (WAIS) may be with global warming. It raising questions about the ice sheet susceptibility to collapse.

The Antarctic octopus - Turquet's octopus - is a little creature that doesn't like moving house. It is a stay-at-home tending to live in one place and only moving short distances to escape predators. Yet when marine scientists looked at the genetic diversity of specimens of the octopus from the Ross Sea and compared them with specimens 10,000kms by sea away in the Weddell Sea they found there was little genetic difference.

To explain how these different populations can be so alike scientists believe there has been at least partial collapse of the West Antarctic Ice Sheet, with the last time perhaps being the previous interglacial period - the Eemian some 125,000 years ago. A partial collapse may have opened up a channel between the Weddell and Ross Seas.

Global Warming on West Antarctic Ice Sheet three times the global average

The West Antarctic Ice Sheet is warming at three times the global average, according to temperature measurements at Byrd Polar Station. This has implications for the melting of the West Antarctic Ice sheet (WAIS) and sea level rise.

The West Antarctic Ice Sheet is inherently unstable due to it's grounding in a deep depression below sea level. Warm Southern ocean currents are already reducing ice shelves holding back ice discharge from glaciers. As these ice shelves are undermined and break up it will allow significant acceleration of glacier discharge increasing the rate of sea level rise.

Lead study author David H. Bromwich from Ohio State University said:

"Our record suggests that continued summer warming in West Antarctica could upset the surface mass balance of the ice sheet, so that the region could make an even bigger contribution to sea level rise than it already does," said Bromwich.

"Even without generating significant mass loss directly, surface melting on the WAIS could contribute to sea level indirectly, by weakening the West Antarctic ice shelves that restrain the region's natural ice flow into the ocean."

Related: Global warming in Antarctica: Thwaites and Pine Island Glaciers | Waking the giant: Global Warming in the Weddell Sea | Southern Ocean warming impact on Antarctic Ice Sheet and global sea level

Waking the giant: Global Warming in the Weddell Sea, West Antarctic Ice Sheet and sea level rise

Warm ocean currents are projected to melt the Filchner-Ronne Ice Shelf in the Weddell Sea area of Antarctica opening instabilities in the West Antarctic Ice sheet (WAIS) which will impact global sea level rise. Climate change is waking up the sleeping giant of Antarctica.

Significant scientific research has been published in recent weeks on the impact of global warming on changing wind patterns and southern ocean currents and the flow-on impact on Antarctic ice shelves and glaciers. The most recent studies reveal the potential instability of the Filchner-Ronne Ice Shelf in the Weddell Sea area. But the real questions to be asked concern the long term stability of the West Antarctic Ice Sheet (WAIS) and how rapidly it could collapse raising global sea levels by up to 6 metres.

I highlighted in November 2011 that the Thwaites and Pine Island Glaciers accelerating, West Antarctic Ice Sheet losing mass in the Amundsen Sea area. Now climate researchers of the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association studying the opposite side of the West Antarctic Ice Sheet (WAIS) in the Weddell Sea area have discovered a mechanism which will drive warm ocean water towards the coast in the later decades of this century, allowing a higher rate of basal melting - the melting from underneath of ice shelves and glaciers by warmer ocean currents - leading to greater discharge of ice from the icesheet.

Another research team has found a large deep basin, about 20,000 square kilometres in size and up to 2 kilometres deep, underneath the ice sheet in the Weddell Sea area, which makes the ice sheet inherently unstable if pinion points for the ice shelf retreat and warmer water enters the basin.

Global Warming in Antarctica: Thwaites and Pine Island Glaciers accelerating, West Antarctic Ice Sheet losing mass

Scientists have been studying the climate change impacts on ice shelfs and glaciers for some time in Antarctica, and particularly around the Antarctic Peninsula where there is substantial warming occurring increasing ice shelf melt and the speed and discharge of glaciers. The most recent studies predict a faster retreat for the Thwaites Glacier and that warm ocean currents are already speeding the melting of the Pine Island Glacier and Ice Shelf and Getz Ice Shelf. A NASA Icebridge flight detected a major new rift in the Pine Island ice shelf on October 14 - the start of the calving of a massive iceberg. A recent paper in Nature Geoscience discusses the Stability of the West Antarctic ice sheet in a warming world and the likelihood of collapse that would raise sea level by more than three metres over the course of several centuries or less.

Related: The Wilkins ice Bridge collapsed in April 2009 as Polar regions felt the heat of climate change. I reported as far back as 2004 that warming in Antarctica was cause for concern with ocean food chain crashing due to Antarctic warming. More recently in April 2011 I discussed Penguin numbers suffering with krill decline due to Global Warming.