Scientists at Sweden’s KTH Royal Institute of Technology have refined a method to measure post-glacial rebound in Fennoscandinavia, revealing a denser-than-expected landmass and a rise rate of up to one centimeter per year.
As the Nordic region continues to rebound from the weight of Ice Age glaciers, its landmass is gradually rising above sea level. Researchers at Sweden’s KTH Royal Institute of Technology have developed a more precise method for measuring and predicting how this slow uplift affects Earth’s gravitational pull over time. Their findings reveal that the landmass of the Fennoscandinavian Peninsula is denser than previously thought.
For decades, KTH scientists Mohammad Bagherbandi and Lars Sjöberg have studied the post-glacial rebound effect in Fennoscandinavia, which includes Sweden, Norway, Finland, and part of Russia. Their latest research introduces a refined measurement technique that integrates satellite remote sensing, terrestrial gravity data, and 3D positioning from GPS and similar satellite-based systems.
The KTH researchers found that the density of the upper mantle is about 3,546 kilograms per cubic meter—slightly more than reported in earlier studies. It is widely believed the land mass rises by as much as 1 cm per year.
The Role of Satellite Data in Geodesy
Bagherbandi, a researcher in geodesy and land surveying at KTH, says the new technique highlights the value of satellite data in the field of geodesy, the science of accurately measuring and understanding the Earth’s geometric shape, orientation in space, and gravity field
“Beginning 60 years ago, scientists were using terrestrial gravimeters to establish gravity reference system and study temporal changes in gravity associated with glacial isostatic adjustment (GIA),” Bagherbandi says. “Our study is an alternative technique to study this phenomenon.”
This means researchers can now create alternative and comparable models of how the land and gravity are changing over time in the region, he says.
“This discovery helps us understand the slow ‘bounce-back’ of land after the Ice Age,” Bagherbandi says. “It also shows how important the Global Geodetic Observing System (GGOS) are for learning about Earth’s movements and gravity changes.”
A similar study is underway in the U.S., where scientists are evaluating an even larger region of North America that is known to be rising.
Bagherbandi says understanding these changes is valuable beyond the field of geodesy. It helps scientists improve their tools for studying Earth’s geodynamics. It can also help with other fields, like preparing for rising sea levels and learning about natural disasters
Reference: “A short note on GIA related surface gravity versus height changes in Fennoscandia” by Mohammad Bagherbandi, and Lars E. Sjöberg, 13 December 2024, Journal of Geodesy.
DOI: 10.1007/s00190-024-01921-7
Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.
7 Comments
Now here is a notion. If geophysicists and geodeticists are smart, they will figure out a way to document rates of Swedish coastal rise to two decimal places, based on the density of the upper mantle, now measured to 3 decimal places. This will then provide a yardstick to measure directly the rate of sea-level rise along the coast of Sweden, assuming that the Baltic Sea is not filling up with rubbish and the water not escaping , although that should not matter assuming that the Danish outlet to the north Sea does not blocked by rising Sweden…………….and bits of Norway……….and Denmark…………
“…, revealing a denser-than-expected landmass and a rise rate of up to one centimeter per year.”
I think that it is worth noting that the solid rock is rising at a rate nearly an order of magnitude greater than the water.
If Sweden can guaranteed to be rising at 1cm per year, and we find that only 9mm separates the top or base of a designated reference rock from sea-level, then………..If we can measure the density of the mantle below Sweden accurately to 3546kg per cubic metre what’s the problem in measuring 1mm of sea-level rise?
An obvious difference is that the density of a material is a constant, while the height of ocean water is continually changing from waves, atmospheric pressure, wind, and thermosteric expansion. Because sea level is always changing, one can never measure the exact same thing twice, inhibiting the ability to cancel out random changes through multiple measurements. It is always harder to hit a moving target.
We have no problem measuring the sea level and its correlation to man made global warming with several agreeing methods globally. And it is relevant for Sweden since the southern coast is succumbing to the sea level rise as in most places (see my own response to the article).
“Between 1901 and 2018, the average sea level rose by 15–25 cm (6–10 in), with an increase of 2.3 mm (0.091 in) per year since the 1970s.[3]: 1216 This was faster than the sea level had ever risen over at least the past 3,000 years.[3]: 1216 The rate accelerated to 4.62 mm (0.182 in)/yr for the decade 2013–2022.[4] Climate change due to human activities is the main cause.[5]: 5, 8 Between 1993 and 2018, melting ice sheets and glaciers accounted for 44% of sea level rise, with another 42% resulting from thermal expansion of water.[6]: 1576 ”
“Between 1901 and 2018, the global mean sea level rose by about 20 cm (7.9 in).[5] More precise data gathered from satellite radar measurements found an increase of 7.5 cm (3.0 in) from 1993 to 2017 (average of 2.9 mm (0.11 in)/yr).[6] This accelerated to 4.62 mm (0.182 in)/yr for 2013–2022.[4] Paleoclimate data shows that this rate of sea level rise is the fastest it had been over at least the past 3,000 years.[3]: 1216
While sea level rise is uniform around the globe, some land masses are moving up or down as a consequence of subsidence (land sinking or settling) or post-glacial rebound (land rising as melting ice reduces weight). Therefore, local relative sea level rise may be higher or lower than the global average. Changing ice masses also affect the distribution of sea water around the globe through gravity.[21][22]”
[“Sea level rise”, Wikipedia]
“We have no problem measuring the sea level and its correlation to man made global warming …”
Thank you for the information from Wiki’. However, the point of the sub-thread was about precision and the number of significant figures. Note that generally your quotes do not include information on the ‘error bars’ or margin of error for the nominal changes or rates of change of sea level. That was the essence of my response to Rob. In the one instance where the precision was implied — “Between 1901 and 2018, the average sea level rose by 15–25 cm (6–10 in), …” — the increase is thus equivalent to 20 cm +/-5 cm, with the range of the uncertainty being +/-5 cm. Using the Empirical Rule, one can approximate the Standard Deviation as being about +/-1 cm, or 1 part out of 5. One can quibble about whether or not +/-1 cm meets the commonly acknowledged meaning of “no problem.” However, +/-20% is not usually considered high precision work.
Correlation does not imply causation.
While Wiki’ implies all sea level increase is the result of humans, that strongly suggests that natural variation (except subsidence and isostatic rebound) has ceased since the beginning of the Industrial Revolution, an improbable event without supporting evidence. Therefore, I reject the numeric claim about the role of humans.
Paleoclimate data has even less accuracy and precision than 20th C measurements (See the error bars on the graph in the Wiki’ article you quoted and note how they are larger at the beginning of the 20th C than currently.) because the estimated changes depend on sampled proxies rather than actual measurements. Furthermore, there is a general principle that time acts like a low-pass filter, suppressing peaks and valleys. Even radiogenic age dating has a percentage error range, influencing the shape of any plots arising from a mix of calculated time and proxy sea levels. That means that claims of “the most in xxx years” are difficult to even support let alone prove. I therefore question the claim about comparison with paleo changes. Note the graph at https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level . First off, there are unexplained minor disagreements between the satellite data and tide stations, such as about 1983, and there are spikes such as at 1882 and 1915 whose short-term rates appear to be greater than anything in recent times. Either one accepts the data as being valid, which undercuts the claims about recent accelerations, or if one rejects the data as being unreliable, then there is no support for the claim of recent ‘accelerations’ being the greatest in 3,000 years.
The figure is an average figure of course, the southern coast from north of Stockholm down is rising slower than the ocean rise. That’s why Stockholm has (somewhat) prepared for larger future floods.