Climate science

Antarctic ice shelf thinning is accelerating, reveals new study

  • 26 Mar 2015, 19:30
  • Robert McSweeney

A new study reveals ice shelves in the western part of Antarctica are melting much faster than a decade ago. Satellite data from three separate missions shows melting of these vast, floating ice shelves has increased by 70% in the last decade.

If current warming trends continue, the researchers say the ice could thin so much that these icy 'gatekeepers' risk collapsing, unlocking parts of the ice sheet to faster ice loss.

Floating sheets of ice

Ice shelves form where a glacier on land reaches the coast and flows into the ocean. They surround 75% of the Antarctic continent. If the ocean is cold enough, the ice doesn't melt but instead forms a floating sheet of ice that extends over the ocean.

Ice Shelf Diagram

Ice shelf diagram. Credit: Professor Helen Fricker, Scripps Institution of Oceanography, UC San Diego.

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Arctic sea ice hits lowest winter peak on record

  • 20 Mar 2015, 12:15
  • Robert McSweeney and Sophie Yeo

The latest satellite data shows the winter maximum extent of Arctic sea ice this year is the lowest recorded since measurements began in 1979. Provisional data from the National Snow and Ice Data Center (NSIDC) in the US shows 2015 has broken the previous record set in 2011 by 130,000 square kilometers.

Warm air temperatures in the Arctic have been a key reason why less ice has formed this winter, the NSIDC says.

It's around this time of year when the freeze-up of Arctic sea ice through the winter hits a peak, and signals the start of the melt season in spring and summer.

Using satellites, scientists can mark this point every year, recording when the Arctic sea ice hit its largest extent and the size it reached.

For 2015, the NSIDC thinks this point was on 25 February, when sea ice covered 14.54 million sq km. At 1.1 million sq km smaller than the 1981-2010 average, this year has set a new record for the lowest winter peak.

Arctic Sea Ice Winter Extent _NSIDC

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Amazon rainforest is taking up a third less carbon than a decade ago

  • 18 Mar 2015, 18:05
  • Robert McSweeney

The amount of carbon that the Amazon rainforest is absorbing from the atmosphere and storing each year has fallen by around a third in the last decade, says a new 30-year study by almost 100 researchers.

This decline in the Amazon carbon sink amounts to one billion tonnes of carbon dioxide - equivalent to over twice the UK's annual emissions, the researchers say.

If this pattern exists in other forests around the world, deeper cuts in human-caused carbon dioxide emissions are needed to meet climate targets, the researchers say.

Three billion trees

The Amazon rainforest is the largest rainforest in the world. Spanning nine countries in South America, it's 25 times the size of the UK.

Using a process known as photosynthesis, the Amazon's three billion trees convert carbon dioxide, water and sunlight into the fuel they need to grow, locking up carbon in their trunks and branches.

As they grow, Amazon trees account for a quarter of the carbon dioxide absorbed by the land each year. Studies suggest that as human-caused carbon dioxide emissions increase, forests will absorb and store more carbon, assuming they have enough water and nutrients to grow.

But a new study, published today in Nature , suggests the Amazon has passed saturation point for how much extra carbon it can take up.

Diminishing carbon sink

A team of almost 500 people monitored trees in more than 300 sites across eight countries. Between 1983 and 2011, the researchers measured the trees in each plot, recording the number, size and density to calculate how much carbon each one stored.

The trees took up more carbon and grew more quickly during the 1990s, before levelling off since the year 2000. You can see this in the middle chart below.

Brienen Et Al (2015) Fig1

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