Saturday , April 17 2021

Winds and waves of the oceans get (slightly) stronger each year



ocean waves

Oceanic winds and waves become slightly stronger each year due to climate change. (Credit: Leo Soby / Neoplas)

In the world of climate science – and science in general – data are being stolen. The more you have it, and the higher its quality, the better. And while such trends as temperature rise and sea level have impeccable data behind them, not every measure of climate change is so happy.

Take, for example, the global wind and wave climate that measures trends in wind speed and the waves in the oceans around the world. Both of these factors influence the interaction between the atmosphere and the ocean of energy and carbon (more winds are steady water, which can reach the way of air transfer to water), and of course the higher waves could cause bigger problems for storm weather and affect flood levels. But historically it was inconvenient to obtain reliable long-term data on these phenomena to study possible trends.

Until now, it is. A paper inside Science today uses satellite data to analyze wind speed and wave height over more than 30 years and concluded that on average both are increasing, especially in the southern hemisphere, and especially in extreme conditions such as storms. They also demonstrated a useful way to study these things in the first place, which should help scientists advance forward.

Defective data

Why is it necessary so far to collect and analyze what should be a fairly clear database? As the authors of the newspaper explain, it was not so easy. Ocean swimmers, "the most obvious source of data," have proven to be problematic since changes over the years in their construction and instrumentation mean that the data they spit is not really consistent in the long run. So, we would compare apples, if not oranges, then at least other types of apples – it's not ideal.

Thus, they turned to the satellite record, which currently runs from 1985 to 2018. Not bad, but the same concerns arose there: With all the different types of hardware and software in space, maybe their data are not sufficiently reliable for such research or?

So, the authors decided to get in and find out. As you can imagine, it worked.

Progresses

In particular, they studied data collected from three types of instruments on satellites: heights that measure the height of the wave and the wind speed; radiometers, which measure the speed of the wind; and spherometers, which measure the speed and direction of the wind.

After cross-checking all the numbers, cross-validating with other satellites and just generally ensuring that they were not fooled by anything, the authors concluded that in the past 30 years they saw a strong positive trend in the global wind speed, and weaker (but still noticeable) rise in the heights of the waves. They also noted that the trends are much stronger in extreme cases, which they defined as data from the 90syou percentil.

Not that any of the current changes is particularly high. Wind speed increases by about one centimeter per second every year – twice as fast as the snail's speed in the garden – across the South Ocean and south of the equator, where the trends are the strongest. The change was about half that in the North Atlantic. (The extreme cases had the same distribution, but at a faster speed, about two inches per second a year.) Things were not quite clear about the height of the wave, but there were patches with a total increase of about a tenth of an inch per year and a surprising place in the North Pacific with a drop of about half an inch a year.

Climate Climate

It may not sound like much, parts of inches here or there, but the results show clear trends for global behavior over time. Any improvement of our understanding of the global climate of the wind and the wave is useful, authors write, because "estimates for future ocean wind and wave states and whether extreme conditions are changing are important elements of the projections of the total sea level."

The team also showed that satellites can be trusted, because each of the various types of instruments observed on a total of 31 satellites orbiting orbiting eventually showed data consistent with each other. This means that future research can rely on this increasingly rich set of data, without having to worry about comparing the apple with anything else.

Therefore, not only did the authors add some specific parts of those important data to the global climate record, they also made it easier for future researchers to do the same.


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