{"id":4359,"date":"2015-09-29T10:33:30","date_gmt":"2015-09-29T09:33:30","guid":{"rendered":"http:\/\/blog.soton.ac.uk\/ggblog\/?p=4359"},"modified":"2015-09-29T10:35:09","modified_gmt":"2015-09-29T09:35:09","slug":"4359","status":"publish","type":"post","link":"https:\/\/blog.soton.ac.uk\/ggblog\/2015\/09\/4359\/","title":{"rendered":"After the supermoon, comes the supertide"},"content":{"rendered":"

After the supermoon, comes the supertide<\/h1>\n

\nThis article was originally published on The Conversation<\/a>. Read the original article<\/a>.<\/h3>\n
\"\"<\/a>
..and high tides. Paul J Martin\/ Shutterstock.com<\/figcaption><\/figure>\n

Ivan Haigh<\/a>, University of Southampton<\/a><\/em> and Kevin Horsburgh<\/a>, National Oceanography Centre<\/a><\/em><\/p>\n

The city of Plymouth, on England\u2019s south coast, normally has fairly moderate tides. However this week it will have a 6m \u201csupertide\u201d<\/a> \u2013 the highest tide in 18 years<\/a>. This comes just days after the celebrated \u201csupermoon\u201d<\/a>.<\/p>\n

In fact, many locations along the UK, US and Australian coasts will experience their highest tides for tens of years around September 29 or 30. Coastal roads in Miami, for instance, have already been closed<\/a> in anticipation of exceptional tides.<\/p>\n

These high tides may bring water levels uncomfortably close to the tops of harbour walks and flood defences, emphasising the threat of rising sea levels. In the UK they are unlikely to be a major problem on their own unless they coincide with storms (a strong storm surge<\/a> has a greater impact than even the most exotic of tides). However in other areas, like in parts of America and the Pacific, no storms are necessary: these high tides on their own can lead to nuisance flooding<\/a>.<\/p>\n

Why do we expect such extreme tides?<\/h2>\n

Tides are controlled by changes in the position and alignment of the moon and sun relative to Earth. Every fortnight \u2013 at new moon or full moon \u2013 the Earth, sun and moon are in an approximately straight line as seen from space and the additional gravitational pull of the sun causes stronger tides, known as spring tides.<\/p>\n