75CFDA33-4183-4D54-9393-81C6E28FAAD9 Created with sketchtool. Rate of Sea Level Rise Up 50% in Two Decades

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  Last updated August 10, 2017 at 4:01 pm

The rate of global sea level rise has increased by 50% over the last two decades, according to new research out today.

Researchers used a new method to analyse the trend for sea level rise which hasn’t been applied to this problem before.  This new method is better able to find the signal among the noise of complicated data sets, and has been used in the past to analyse seismic data. The benefit of using this type of method is that it can separate out short term natural variations (for example variability around El Nino/la Nina cycles) from the long term trend.

And the long term trend is not looking good. Sea level rise can happen a number of ways. Firstly – water takes up more space as it gets warmer. This is called thermal expansion. Thermal expansion was responsible for about 50% of global sea-level rise in 1993, but the proportion of this has dropped over the last few decades, as the proportion of sea level rise from melting ice sheets took over.

The second way you can get sea level rise is by there simply being more water in the oceans. This happens as glaciers and ice sheets melt. In 1993 the melting of the Greenland Ice Sheet contributed about 5% of the sea level rise, but this has jumped up to 25% of sea level rise in 2014, as the melting of the ice sheet accelerates.

Even addition of water from human activities like groundwater extraction and depletion and deforestation contribute (although to a much smaller degree) to sea level rise. About 80% of groundwater humans extract eventually ends up in the ocean.

Adelaide (Birkenhead and surrounding region) under a low (0.5m) sea-level rise projection in 2100. Credit: OzCoasts.

Australians do love to live beside the seaside. Around 85% of us live in coastal areas. Some closer than others – there’s currently over 39,000 Aussie homes built within 110m of the ocean, built on soft soils that could be eroded away by rising sea levels. OzCoasts, developed by Geoscience Australia, let’s you explore what city maps might look like given current trends of sea level rise by 2100.

This new research is yet another piece of evidence that points out the urgency of mitigating climate change so that we’ll be prepared to deal with the impacts.

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Lisa Bailey


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