(ORDO NEWS) — In a warmer world, rising sea levels could render many coastlines, beaches and reef islands uninhabitable or destroy them entirely. The earth has been warming since pre-industrial times, which has already raised sea levels by 20 centimeters.
Research shows that some coastlines and even low-lying coral reef islands are actually growing rather than collapsing in the face of rising sea levels. It occurs on some beaches in Queensland and New South Wales in Australia, as well as on the coasts of Asia and Africa.
This goes against the common understanding of how climate change impacts coastlines and has led to confusion that has been deliberately introduced into the public discourse by climate change deniers in part. So what’s going on?
Shores and sediments
In order to understand this phenomenon, we first need to understand the sand drift situation. A “positive” sediment balance is when more sand enters the beach than leaves.
With a “negative” balance, more sand is taken out than is taken in. Over time, a positive sediment balance stimulates coastal growth and beaches expand further into the ocean.
Rising sea levels, on the other hand, wash sand off the beach and move it to other places along the coast. This can result in the loss of sand from the beach and the coastline will recede inland.
So, if the planet’s sea levels are rising, why do some beaches keep rising?
The answer is that a positive sediment balance is currently having a greater impact on growing beaches than erosion due to sea level rise. In other words, the amount of sand that comes ashore is greater than the amount lost when the sea level rises.
What does this mean for the future?
The Intergovernmental Panel on Climate Change (IPCC) predicts that by 2100 sea levels will rise by 1.01 meters (versus 1995-2014 levels) if global emissions do not decrease.
Moreover, sea level rise is getting faster. The IPCC found that it grew by 1.3 millimeters per year during 1901–1971, by 1.9 millimeters per year during 1971–2006, and by 3.7 millimeters per year during 2006–2018.
This rise in sea level may result in sediment being carried onto the beach, which the current positive sediment balances can no longer compensate for. This circumstance can provoke the erosion of the beaches, which are currently growing.
Therefore, it is important that currently rising coastlines are not taken as evidence that rising sea levels are not causing coastal erosion.
As well as the fact that such coasts are free from the risk of erosion in the future. Even if there is enough sediment to support coastal growth, dangerous erosion and flooding due to storms and cyclones can still occur.
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