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Executive Summary for April 6th

In our weekly summary, we report on the value of coral reefs in protecting coasts, a new method of underwater navigation and predictions for ice-free Arctic summers.

Published on April 6, 2018 Read time Approx. 2 minutes

How Coral Reefs Could Save Your Life

During a hurricane, it pays to have a coral reef by your side. That’s the conclusion of a new study that measured how Ningaloo Reef – Australia’s largest fringing reef – shielded the country’s west coast from Category 3 storm waves in 2015.

The study by researchers at the University of Western Australia found that Tropical Cyclone Olwyn spawned 6m (nearly 20ft) waves and 140kph (87mph) winds that battered the ocean-facing part of the reef. But the levels of beach erosion were not nearly as bad as they might have been. The little erosion that did occur was due to winds acting only within the nearshore lagoon. Similar cyclones, the study found, had caused up to 10 times more erosion on beaches without fringing reefs.

Few studies have quantified the hurricane protection that reefs provide. However, Mexico is taking out the world’s first insurance policy on a coral reef to aid restoration after large storms because of the value of protection such reefs offer coastal areas.

Razor-Thin Margins for Ice-Free Arctic

Whether or not the Arctic Ocean experiences ice-free summers in the future may come down to a narrow range of warming air temperatures, new research shows.

Warming of 1.5 C (2.7 F) this century – in line with targets set by the 2015 Paris Agreement – would mean only a 30 percent chance of ice-free summers, according to the study published in the journal Nature Climate Change. Warming by 2 C (3.6 F), however, would make an ice-free summer a near certainty. More warming than that could mean an end to sea ice much sooner.

Sea ice is a key part of the Arctic Ocean ecosystem, providing hunting platforms for polar bears and the right conditions for plankton to thrive. As sea ice melts, activities such as shipping and tourism are expected to boom and more geopolitical conflicts may arise.

Underwater GPS?

University of Illinois researchers think they’ve developed a new form of underwater navigation, according to a study in the journal Science Advances.

A team modified an underwater camera called Mantis Cam (inspired by the eyes of mantis shrimp). Paired with a compass and tilt sensor, the camera can discern data on how light polarizes underwater. The team realized there were patterns and they were linked to the sun’s position in the sky relative to the camera’s location. Thus, by knowing the date and time of the data, they could discern GPS coordinates and say they can locate position within an accuracy of 61 km (38 miles).

In the study, they write that the technology could enable more cost-effective autonomous navigation and help lead to new insights into the navigation behaviors of migratory marine species. They also suggest that it may offer a new avenue for exploring how air or water pollution affects migratory species, such as whales, that are sensitive to polarized light.

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