Rising sea levels brought on by a warming planet are a very serious threat to many coastal communities living in every corner of the globe, from Miami in Florida to Mumbai in India. But the melting of glaciers may also have another curious effect, as it seems that the UK could lose some its mountains – sort of.
The Ordnance Survey, the national agency responsible for mapping Great Britain, traditionally measures mountain peaks from sea level, taking the mean from between high tide and low tide. If the absolute height comes in above 609.6 meters (2,000 feet) tall, then it is classed as a mighty mountain; anything below and it is relegated to a humble hill. But there are plenty of mountains across the UK that make the grade by just a few centimeters.
For example, the mountain Thack Moor, located in Cumbria in the north of England, was up until very recently thought to be just 609 meters tall, meaning it was not quite lofty enough. It was not until 2013 that a more accurate reading of the peak found that it was actually 609.62 meters high, giving it the prestigious official mountain status. But with only a measly two centimeters of buffer room, it wouldn’t take much to knock Thack Moor off its perch.
Sea levels are rising. NASA/CSIRO
The fact that sea levels are rising has been documented around the globe. NASA has calculated that since 1993 the world’s oceans have been rising by an average of 3.4 millimeters per year. The National Oceanic and Atmospheric Administration has found that sea levels have been rising by around 1.5 centimeters (0.6 inches) every decade since 1900. However, since 1992, it is now more like 3 centimeters (1.2 inches) per decade. At this rate, it won’t take long for Thack Moor to lose its crown again.
The melting of the glaciers in Greenland is thought to be a very immediate threat. If just the single Zachariæ Isstrøm glacier in the northeast of the island were to melt, for example, the global sea level would rise by an incredible 46 centimeters (18 inches), and there are worrying hints that this might already be happening. The rate at which the ice is sliding off the land and into the water has increased since 2012, losing an average of 4.5 billion tonnes (5 billion tons) per year (and even this might be an underestimate).
Whether or not these pointy prominences are mountains or hills is neither here nor there, and won’t fundamentally affect anything apart from those few hardcore mountaineers who wish to climb all of Great Britain’s peaks. But it does raise an interesting point about the unforeseen consequences that might emerge as climate change really sets in.