With global warming, fluctuations in sea levels expected to increase – Maui News

With a king tides advisory up for the state Tuesday, University of Hawaii scientists warn in a published paper that Earths warmer temperatures will expand oceans and generate higher seas that coincide with high tides that will become more extreme this century.

We looked at how accelerating thermal expansion will affect the variability of sea level, so we go beyond the projections of sea level rise, and we look at annual and year-to-year fluctuations in the sea level, said lead scientist Matthew Widlansky, associate director of the UH-Manoa Sea Level Center. If the ocean continues to warm, that thermal expansion that drives these sea level fluctuations accelerates.

What that means ultimately for Hawaii is that the tendency for king tides will become more extreme in the future with continued greenhouse warming.

In a yearlong study published in Communications Earth and Environment in August, UH scientists assessed sea level projections into the year 2100 in the context of the Earths climate responding to greenhouse warming. They analyzed 29 computer global climate models.

While future sea level changes remain uncertain in many locations, all 29 computer models concluded that theres a strong possibility that sea level fluctuations will increase in the future because of how oceans expand faster at higher temperatures.

In a UH news release, Fabian Schloesser, a researcher at the Sea Level Center who collaborated on the study, said that sea level variability increases in a warmer climate because the same temperature variations, for example related to the seasonal cycle, cause larger buoyancy and sea-level fluctuations.

In the study, upper-ocean temperatures worldwide were predicted to rise about 35 degrees by the end of the century with sea level fluctuations increasing by 4 to 10 percent on a seasonal-to-inter-annual timescale.

Theres been a lot of study of how greenhouse warming is likely to cause the increasing melting of land ice, so that causes more water to flow into the ocean, and also if the ocean warms, the water expands, Widlansky said Tuesday in a phone interview. Its also well studied and shown that the expansion of the ocean, that scientists call thermal expansion, is accelerating.

For Hawaii, this means loss of beaches, coastlines and damaged coral reefs impacts already seen at places like Baldwin Beach Park, Kaanapali Beach and along South Kihei Road.

On Monday, the National Weather Service issued a sea level rise warning for the state over the next few days during the afternoons and evenings. The weather service observed ocean water levels to be about half a foot higher than expected.

Combined with high astronomical tides and the new moon, coastal flooding is anticipated at beaches that are normally dry, the weather service said. Some minor coastal erosion also may occur, as well as saltwater contact with low-lying roads, docks, boat ramps and other coastal infrastructure.

Widlansky said that Hawaii experiences its largest tides during the summer and winter months, but more so at the end of summer when the ocean is at its warmest and takes up a little bit more volume and space.

Kahului coastal areas hit record-high monthly sea levels in June and July, he said.

So the high tides during the summer plus the high sea levels, thats what gives us the summer king tides, he said.

Overall, conducting this study and observing the environmental changes reinforce the need for monitoring and forecasting agencies like the weather service and other programs that monitor the tides and other conditions.

This is the type of work that we do at the UH Sea Level Center, he said. That type of monitoring, and eventually improving future outlooks, I think are going to be more and more important for mitigating and adapting to some of these coastal hazards.

For more information regarding the study, visit https://www.nature.com/articles/s43247-020-0008-8#Sec8.

* Dakota Grossman can be reached at dgrossman@mauinews.com.

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With global warming, fluctuations in sea levels expected to increase - Maui News