From the University of Southampton
Land-ice decay at the end of the last five ice-ages caused global sea-levels to rise at rates of up to 5.5 metres per century, according to a new study.
An international team of researchers developed a 500,000-year record of sea-level variability, to provide the first account of how quickly sea-level changed during the last five ice-age cycles.
The results, published in the latest issue of Nature Communications, also found that more than 100 smaller events of sea-level rise took place in between the five major events.
Dr Katharine Grant, from the Australian National University (ANU), Canberra, who led the study, says: “The really fast rates of sea-level rise typically seem to have happened at the end of periods with exceptionally large ice sheets, when there was two or more times more ice on the Earth than today.
“Time periods with less than twice the modern global ice volume show almost no indications of sea-level rise faster than about 2 metres per century. Those with close to the modern amount of ice on Earth, show rates of up to 1 to 1.5 metres per century.”
Co-author Professor Eelco Rohling, of both the University of Southampton and ANU, explains that the study also sheds light on the timescales of change. He says: “For the first time, we have data from a sufficiently large set of events to systematically study the timescale over which ice-sheet responses developed from initial change to maximum retreat.”
“This happened within 400 years for 68 per cent of all 120 cases considered, and within 1100 years for 95 per cent. In other words, once triggered, ice-sheet reduction (and therefore sea-level rise) kept accelerating relentlessly over periods of many centuries.”
Professor Rohling speculates that there may be an important lesson for our future: “Man-made warming spans 150 years already and studies have documented clear increases in mass-loss from the Antarctic and Greenland ice sheets. Once under way, this response may be irreversible for many centuries to come.”
The team reconstructed sea-levels using data from sediment cores from the Red Sea, an area that is very sensitive to sea-level changes because it’s only natural connection with the open (Indian) ocean is through the very shallow (137 metre) Bab-el-Mandab Strait. These sediment samples record wind-blown dust variations, which the team linked to a well-dated climate record from Chinese stalagmites. Due to a common process, both dust and stalagmite records show a pronounced change at the end of each ice age, which allowed the team to date the sea-level record in detail.
The researchers emphasise that their values for sea-level change are 500-year averages, so brief pulses of faster change cannot be excluded.
The study was funded primarily by Natural Environment Research Council (NERC) and the Australian Research Council (ARC).
Just discussing this with a friend at Southampton Uni. Where did the opening diagram come from as I can’t seem to see it in the report for which I have the following link: http://www.nature.com/…/ncomms4635/full/ncomms4635.html
Will this do for what you are looking for?
http://commons.wikimedia.org/wiki/File:Post-Glacial_Sea_Level.png
OOOPS ….. THIS ONE
http://commons.wikimedia.org/wiki/File:Post-Glacial_Sea_Level.png#file
Search on the phrase “Holocene sea level high stand” and you will receive numerous hits that document empirical evidence of such stands. What I find even more interesting is the number recent papers that are attempts to bring the monster to heel and make it fit with the fad to attribute current sealevel change to anthropic causes. In essence the early-mid Holocene high stands are more of a problem to AGW than the MWP and there is very active work being pursued to make the idea go away.
Somehow that link got all messed up
Hey, I thought 5 meters of sea level rise would be a huge problem to our coastal cities. Now I understand it happens all the time! Thanks, folks!
Interesting and very actual topic, indeed. We are really risking our lives by not paying attention to what we are doing to our planet…. In addition to that, I have also studied another topic, linked to this one: all the recent wars led by humans are also responsible for the climate change and global warming process. You can find more about that here: http://www.1ocean-1system.de/Chapter_e.pdf
Shall we do a little basic math here?
“An international team of researchers developed a 500,000-year record of sea-level variability…”
““This happened within 400 years for 68 per cent of all 120 cases considered, and within 1100 years for 95 per cent.”
500,000 divided by 120 events equals ~4,166 years per event, on average. That is NOT very long in between RISES.
And THEN the time for the changes to take place was 10% of the interval till the NEXT sea level RISE? 68% of the time? And then there was the 95% which happened within 1100 years which is 26% of the whole interval between sea level RISES.
Why did I capitalize “RISE” and “RISES”? Because one has to consider that between many of the rises were also sea level FALLS.
With rises AND falls, it sounds like much of – if not MOST OF – the time that sea level is either rising or falling, but not both. If the sea level fall times are roughly equal to the sea level rise times (they may be longer), then we have a situation on our planet where about 50% of the time or more is spent in rising or falling sea levels, meaning only about half the time (if that) the sea levels are static. Perhaps less static durations – depending on how long the sea level falls took.
And don’t forget, that if 95% occur within 1100 years, 5% take LONGER.
All of this makes me become very skeptical of this paper.
There is information worth investigating from archaeology. From memory:
– submerged areas off the east coast of the US, noted in the book “Across Atlantic Ice” whose theory is that North America was first populated by people from central west coast of Europe who travelled along the edge of the ice as an ice age faded. (They think that people came from Asia along the west coast a few thousand years later, and via Siberia and Alaska also later – some debate about when the combination of a land bridge and an ice-free corridor south actually existed at the same time.) On either coast the archaeological challenge is cost of looking underwater.
– reports from the west coast of BC of changes in spear points as cessation of sea level change greatly affected fresh exposing of rocks.
– investigation now going on to check suspicion that there are rock structures now underwater off the coast of Haida Gwai/Queen Charlotte Islands, of type known to have been created by tribal people to enhance/harvest marine life at river mouths. Sonar data captured last summer is now being analyzed.
But caution is needed to distinguish sea level rise from ground collapse as a cause, the latter happened to an area of Lake Cowichan in the 1940s – caused by an earthquake, a double shock to a tribal group whose village was on the shore.
I don’t know if the village now submerged under Esquimalt Lagoon east of Victoria BC was due to ground collapse or sea level rise, a few thousand years ago IIRC.
(As with many other civilizations, west coast tribal groups located near the water, in their case especially to be near the sea life they harvested, and like many others for water as means of transportation using water craft (in those two cases canoes formed by hacking out the centre of cedar logs were common). But as around the world, defensibility was a factor, so settlements may have been seasonal.)