Ocean floors SHRINKING under weight of melting glaciers, study says | Science | News


Scientists suggest the impact of warming seas has been underestimated and the impact is far worst than first thought.

And melting glaciers are also a key factor putting pressure on the ocean, the papers, published by the Geophysical Research letters show.

It is thought that the rising sea levels could have an impact on the entire planet – but put people who live near coastlines or who rely on the sea are in danger in the near future. 

The study was carried out by Dutch and Australian geologists, led by Thomas Frederikse, of the Delft University of Technology, in the Netherlands.

He found significant changes in land ice mass are changing the ocean and suggests we’ve been underestimating annual sea level rise from 1993 to 2014 by 0.13 millimetres.

He said: “Due to changes in the land ice mass balance and land hydrology, the oceans have gained mass over the past decades, which results in an increase in the total load on the ocean bottom.

“Under this increasing load, the ocean floor will subside due to elastic deformation.”

The research, published in December, used data collected from 1993 to 2014. It found that the ocean floor shrank 0.0004 inches per year. 

The report states: “Over 1993-2014, the resulting globally averaged geocentric sea level change is eight per cent smaller than the barystatic contribution. Over the altimetry domain, the difference is about five per cent, and due to this effect, barystatic sea level rise will be underestimated by more than 0.1mm/yr over 1993-2014.”

According to the research, previous estimates of sea level rising in the Arctic Ocean have been inaccurate by a millimetre each year. 

The discrepancy happened because there is such a huge difference between geocentric sea level and barystatic sea levels. 

Geocentric sea levels are sea level as measured from the centre of the Earth and barystatic sea level is the mass of water in the sea. 

Peter Hess, from Inverse Science reports: “The Earth has had basically the same amount of water for billions of years, so it may sound odd that the seafloor is sinking due to increased ocean water mass. 

“The explanation for this is pretty simple, though: Water is denser than ice, so when sea-based ice masses melt and mix with the ocean, they increase the average density of the ocean. 

“In addition, land-based glaciers and ice-masses are melting into the ocean, exacerbating the ocean’s mass, and increasing the weight ocean floors have to withstand.”

Measuring sea level rises by satellite, like NASA has done for 25 years, records only geocentric sea level, since satellites measure altitudes but it did not determine how a sinking seafloor hid the actual increase in ocean water mass.

The study reports: “Because satellite altimetry observes sea level in a geocentric reference frame, global mean sea level estimates derived from altimetry will not observe the increase in ocean volume due to ocean bottom subsidence, and hence, they may underestimate GMSL rise.” 



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