The trends could be bad news for coastal communities, which face serious risks from sea level rise and extreme storm events, Young says. And although average wave heights there have increased by just 0.3 centimeters per year, the top 10% highest has grown by an average of 1 centimeter per year- a growth of 30 centimeters since 1985, they report today in Science. For instance, although average wind speeds there have increased by 2 centimeters per second each year, the speed of the top 10% fastest winds has increased by 5 centimeters per second per year. In the Southern Ocean, the trends are particularly strong.
When they were done, two trends stood out: Since 1985, average ocean wind speeds in most of the world have increased between 1 centimeter and 2 centimeters per second per year, leading to increases in wave height in many places. To minimize those discrepancies, physical oceanographer Ian Young at the University of Melbourne in Australia, and mathematician Agustinus Ribal at Hasanuddin University in Makassar, Indonesia, compared information from different satellites and calibrated their data against an independent data set collected by a global network of buoys floating in the ocean. But interpreting the data is difficult: Different satellites can give different estimates of wind speed, for instance. Other satellite instruments monitor changes in the reflectivity of the ocean surface, which is reduced by wind-generated ripples, to estimate the speed of ocean winds. By bouncing energy pulses off wave crests and measuring the time those pulses take to come back, instruments called altimeters aboard satellites can measure wave height-the taller the waves, the faster the signal returns. "If at high tide, it could be potentially catastrophic."įor the past 33 years, global satellites have been collecting data on ocean waves-and the winds that drive them. Peter Ruggiero, a geophysicist at Oregon State University in Corvallis who was not involved in the study, calls the increase "substantial," and says he is particularly concerned by evidence that the tallest waves are gaining height at the fastest rate.
Now, a new study suggests the biggest waves there- already the world's largest-are getting bigger, thanks to faster winds attributed to climate change. The frigid Southern Ocean is well known for its brutal storms, which can sink ships and trigger coastal flooding on distant tropical islands.
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