{"id":23179,"date":"2020-12-03T01:49:04","date_gmt":"2020-12-03T01:49:04","guid":{"rendered":"https:\/\/www.lifeandnews.com\/articles\/?p=23179"},"modified":"2020-12-04T06:35:54","modified_gmt":"2020-12-04T06:35:54","slug":"what-makes-the-worlds-biggest-surfable-waves","status":"publish","type":"post","link":"https:\/\/www.lifeandnews.com\/articles\/what-makes-the-worlds-biggest-surfable-waves\/","title":{"rendered":"What makes the world’s biggest surfable waves?"},"content":{"rendered":"

Sally Warner<\/a>, Brandeis University<\/a><\/em><\/p>\n

On Feb. 11, 2020, Brazilian Maya Gabeira surfed a wave off the coast of Nazar\u00e9, Portugal,<\/a> that was 73.5 feet tall. Not only was this the biggest wave ever surfed by a woman, but it also turned out to be the biggest wave surfed by anyone in the 2019-2020 winter surfing season \u2013 the first time a woman has ridden the biggest wave of the year<\/a>.<\/p>\n

As a female surfer myself \u2013 though of dubious abilities \u2013 this news made me really excited. I love it when female athletes accomplish things that typically garner headlines for men. But I am also a physical oceanographer and climate scientist<\/a> at Brandeis University. Gabeira\u2019s feat got me thinking about the waves themselves in addition to the surfers who ride them.<\/p>\n

What makes some waves so big?<\/p>\n

\"A<\/a>
After Hurricane Epsilon moved into the North Atlantic in late October, it sent a huge swell to Europe, including at Nazar\u00e9.<\/span>
\nNOAA via Wikimedia Commons<\/a><\/span><\/figcaption><\/figure>\n

Waves start with a storm<\/h2>\n
\"A<\/a>
Just like ripples in a pond, waves in the ocean propagate outward from the storm that generated them.<\/span>
\nGarrett Sears via Unsplash<\/a>, CC BY<\/a><\/span><\/figcaption><\/figure>\n

Think for a few seconds about what happens when you throw a stone into a serene pond. It creates a ring of waves \u2013 depressions and elevations of the water\u2019s surface \u2013 that spread out from the center.<\/p>\n

Waves in the ocean act similarly. On rare occasions earthquakes and landslides can generate waves, but usually waves are created by wind. Generally, the biggest and most powerful wind-generated waves are produced by strong storms<\/a> that blow for a sustained period over a large area.<\/p>\n

The waves that surfers ride originate in distant storms far across the ocean. For instance, the wave that Gabeira surfed at Nazar\u00e9 was likely generated by a storm somewhere between Greenland and Newfoundland a few days earlier. The waves within a storm are usually messy and chaotic, but they grow more organized as they propagate away from the storm and faster waves outrun slower waves.<\/p>\n

This organization of the waves<\/a> creates \u201cswell,\u201d or regularly spaced lines of waves. When describing a swell, oceanographers and surfers generally care about three attributes. First, the height \u2013 how tall a wave is from the bottom to the top. Then the wavelength \u2013 the distance between the top of one wave and the top of the wave behind it. And finally the period \u2013 the time it takes for two consecutive waves to reach a fixed location.<\/p>\n

\"A<\/a>
As the seafloor gets shallow, it starts to affect waves moving toward shore.<\/span>
\nR\u00e9gis Lachaume via Wikimedia Commons<\/a>, CC BY-SA<\/a><\/span><\/figcaption><\/figure>\n

Seafloors control the waves<\/h2>\n

Waves are not just sitting on top of the ocean. Their energy extends far below the surface, sometimes as deep as 500 feet. When waves move into shallower water close to shore, they start to \u201cfeel\u201d the ocean\u2019s bottom. When the bottom pulls and drags on the waves, they slow down, get closer together and grow taller.<\/p>\n

As the waves move toward shore, the water gets ever more shallow and the waves keep growing until, eventually, they become unstable and the wave \u201cbreaks\u201d<\/a> as the crest spills over toward shore.<\/p>\n

\"A<\/a>
The Nazar\u00e9 Canyon, the dark winding depression extending horizontally across this aerial map, funnels and focuses wave energy toward one spot on the Portuguese coast, producing some of the biggest waves on Earth.<\/span>
\nR\u00fadisicyon via Wikimedia Commons<\/a>, CC BY-SA<\/a><\/span><\/figcaption><\/figure>\n

When a swell is traveling through the ocean, the waves are all more or less the same size. But when swells run into a coastline, waves at one beach can be many times bigger than waves at another beach a mere mile away. So why don\u2019t we find large waves breaking on all shores? Why are there some spots like Nazar\u00e9 in Portugal, Mavericks in California and Jaws in Maui that are notorious for having big waves?<\/p>\n

It comes down to what\u2019s at the bottom of the ocean.<\/p>\n

Most coasts do not have a smooth, evenly sloping bottom extending from the deep ocean to shore. There are reefs, sand banks and canyons that shape the underwater terrain. The shape and depth of the ocean floor is called the bathymetry.<\/p>\n

[The Conversation\u2019s science, health and technology editors pick their favorite stories.<\/em> Weekly on Wednesdays<\/a>.]<\/p>\n

Just as light waves and sound waves will bend when they hit something or change speed \u2013 a process called refraction \u2013 so do ocean waves. When shallow bathymetry slows down a part of a wave, this causes the waves to refract. Similar to the way a magnifying glass can bend light to focus it into one bright spot, reefs, sand banks and canyons can focus wave energy toward a single point of the coast<\/a>.<\/p>\n

This is what happens at Nazar\u00e9 to create giant waves<\/a>. Extending out to sea from the shore is an underwater canyon that was etched out by an ancient river when past sea level was much lower than it is today. As waves propagate toward shore over this canyon, it acts like a magnifying glass and refracts the waves toward the center of the canyon. This focusing of waves by the Nazar\u00e9 Canyon helps make the largest surfable waves on the planet.<\/p>\n

The next time you hear about someone like Maya Gabeira surfing a record-breaking wave at Nazar\u00e9, think about the faraway storms and the unique underwater bathymetry that are essential for generating such big waves. The wave she rode had been on a long journey, and at its crashing end, it was memorialized as she took off from its crest and rode down its huge, steep face.\"The<\/p>\n

Sally Warner<\/a>, Assistant Professor of Climate Science, Brandeis University<\/a><\/em><\/p>\n

This article is republished from The Conversation<\/a> under a Creative Commons license. Read the original article<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

Sally Warner, Brandeis University On Feb. 11, 2020, Brazilian Maya Gabeira surfed a wave off the coast of Nazar\u00e9, Portugal, that was 73.5 feet tall. Not only was this the biggest wave ever surfed by a woman, but it also turned out to be the biggest wave surfed by anyone in the 2019-2020 winter surfing […]<\/p>\n","protected":false},"author":44,"featured_media":23180,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1862],"tags":[8831,4451,2800,1188,9091,9090,9089,256],"_links":{"self":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/23179"}],"collection":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/users\/44"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/comments?post=23179"}],"version-history":[{"count":3,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/23179\/revisions"}],"predecessor-version":[{"id":23184,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/23179\/revisions\/23184"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media\/23180"}],"wp:attachment":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media?parent=23179"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/categories?post=23179"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/tags?post=23179"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}