Southern sea levels rise drastically

Apr 12, 2012

(Phys.org) -- Sea levels have risen about 20cm in the South West Pacific since the late 19th century, a new scientific study shows.

Sea levels in Tasmania remained relatively stable for much of the past 6000 years but around 1880 they started rising drastically, said Dr Patrick Moss from the School of , Planning and at The University of Queensland.

Between 1900 and 1950, relative sea level rose at an average rate of 4.2 mm per year.

“Overall the rate of 20th century sea level rise reconstructed from our data is 1.5 mm per year,” said Dr Moss, who co-wrote a report on the study with scientists from Plymouth University (UK), the Victoria University of Wellington (NZ), Queens University Belfast (UK), the University of Tasmania and University of Southampton (UK).

The highest rates of sea level rise occurred in the 1910s (.3 - .8 mm per year) with a second peak in the 1990s.

“The rise in 1910 probably reflects the end of the little ice age, when temperatures were about one to two degrees cooler in the northern hemisphere than today,” Dr Moss said.

“The 1990s peak is most likely indicative of human-induced climate change.”

The study used sediment cores from Tasmania's salt marshes to reconstruct a record of past sea levels.

“The surface of the marshes builds up over time in response to tidal inundation, providing an accurate record for sea level change,” Dr Moss said.

“Sea level observations in Australia only go back as far as European settlement.

“By comparing our measurements to official observations we can look at long-term changes in sea levels.”

Sediment layers in the core samples also provided physical evidence of the start of logging in Tasmania, when nuclear testing was at its peak globally, and the introduction of unleaded petrol.

Dr Moss said an accurate measurement of past sea levels had significant implications for understanding sea level rise under a changing climate.

“Any drastic changes from the norm, which persist for several decades and over a wide area, represent important climate signals,” Dr Moss said.

“This in turn has implications for where we build our cities and infrastructure.”

The results of the study, published in Earth and Planetary Science Letters, indicate that the magnitude of sea level rise is much higher in the South West Pacific than elsewhere on the planet and that this could be attributed to ice-melt from sources in the northern hemisphere.

“A large ice-melt is like a fingerprint,” Dr Moss said. “When such a significant mass shifts around the earth's surface we can detect its movement.

“Based on this, it appears likely that the primary source of sea level rise in the Southern Hemisphere is the Greenland Ice Sheet, but also mountain glaciers in Alaska, western North America and the Canadian Arctic.”

The group of scientists will do further research in and the South Island of New Zealand, with the aim of creating a more complete picture of the extent of rise in the South West Pacific.

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tadchem
not rated yet Apr 12, 2012
20 cm in a little over a century? That just about half the 3m rise in the last 7000 years during the post-glacial Holocene.
GSwift7
2.3 / 5 (6) Apr 12, 2012
The study is available for free at the link embedded in the above article. Anyone interested should take a look. I congratulate the team for making their paper available at a free source.

As usual with this kind of story, there are some important points from the scientific paper which the press release does not mention. The study seems to be a good, non-biased study of regional sea level, and an honest attempt to compare different records from that region. Here's an excerpt:

Linear trends (uncorrected for crustal motion) are variable and, when calculated from 1930, range from 0.9 mm/yr (Fremantle) to 2.6 mm/yr (Newcastle). There is little evidence for any accelerations in these records over this time period


there's a nice diagram of the data.

In the results section, they say the estuary was dry from around 1400 to 1800. They didn't adjust for the hight of the land changing over time either. That's why they say "relative" sea level.
GSwift7
1.8 / 5 (6) Apr 12, 2012
tadchem:

20 cm in a little over a century? That just about half the 3m rise in the last 7000 years during the post-glacial Holocene


They said 1.5 mm/year overall in their data, which is 1.5 cm per century, not 15 cm. If your 20 cm was correct, that would be 2 meters, which is two thirds of 3 meters (more that half of 3 meters).

However, their figure 5b (near the bottom of the study) shows that sea level only rose from about 1880 to 1940. It was steady before and after that period. In that time period it changed about .3 m, so that's about 5 mm/year for 60 years. They don't show any sea level rise from the mid-1900's to now in this location. Once again, that's relative to land height though. If the land rose, it would hide a rise in sea level in this paper.
GSwift7
1.8 / 5 (5) Apr 12, 2012
oops, my bad. 20 cm should be .2 meters, which is nowhere near half of 3 meters. Either way, your "nearly half" isn't what the study says.
GSwift7
2.2 / 5 (6) Apr 12, 2012
One more interesting conflict between what the story above says and what the study itself says:

From the results section of the study, in the paragraph right before Table 3:

The hypothesis that northern hemisphere ice masses were the main contributor to global sea-level rise in the early part of the 20th century requires further testing, for example by obtaining new proxy sea-level records from other sites in the Southern Hemisphere


So, it's a little early to say on that one. The press release makes it sound so certain.

Immediately before the part I quoted they go into the reasons for uncertainty, but you can look it up if you really want to know.
rockwolf1000
1 / 5 (1) Apr 12, 2012
tadchem:

20 cm in a little over a century? That just about half the 3m rise in the last 7000 years during the post-glacial Holocene


They said 1.5 mm/year overall in their data, which is 1.5 cm per century, not 15 cm. If your 20 cm was correct, that would be 2 meters, which is two thirds of 3 meters (more that half of 3 meters).

However, their figure 5b (near the bottom of the study) shows that sea level only rose from about 1880 to 1940. It was steady before and after that period. In that time period it changed about .3 m, so that's about 5 mm/year for 60 years. They don't show any sea level rise from the mid-1900's to now in this location. Once again, that's relative to land height though. If the land rose, it would hide a rise in sea level in this paper.


1.5mm per year = 15 cm per century not 1.5 cm which would be a ten year period
Lurker2358
4.2 / 5 (5) Apr 12, 2012
1.5mm per year = 15 cm per century not 1.5 cm which would be a ten year period


Yeah.

20 cm in a little over a century? That just about half the 3m rise in the last 7000 years during the post-glacial Holocene.


No.

3m = 300cm

300cm/7000yr = 0.043cm/yr or 0.43mm/yr

2012 - 1880 = 132yr

20cm/132yr = 0.152cm/yr or 1.52mm/yr

Which means for the past 132 years the sea level rose an average of 3.53 times faster than the average in the previous 7000 years.

To me, that is statistically significant in terms of many sciences, meteorology, climatology, geology, etc.

Which may suggest that as much as 72% of sea level rise in the past 132 years is man-made...
kaasinees
0.9 / 5 (27) Apr 12, 2012
even 7000 thousand years ago we could have been the cause of rising sea.
After all burning down forests and building farms on that land was a common and old practise by humans.
Now we just have speed it up even more with massive agriculture, transportation and coal burning.
We really are a bad bacteria on the planet.
nuge
3 / 5 (3) Apr 13, 2012
even 7000 thousand years ago we could have been the cause of rising sea.
After all burning down forests and building farms on that land was a common and old practise by humans.
Now we just have speed it up even more with massive agriculture, transportation and coal burning.
We really are a bad bacteria on the planet.


I really don't think the level of human-caused climate change 7000 years ago could have been anything other than negligible next to other factors. There simply weren't enough people around. It has only been since the start of the industrial age that human impact has been of great enough scale to cause a substantial amount of change to the global climate.
kaasinees
0.5 / 5 (25) Apr 13, 2012
I really don't think the level of human-caused climate change 7000 years ago could have been anything other than negligible next to other factors

You think wrong.
Entire deserts have been made due to this human activity.
They burned down a whole patch of forest and build farmland on it:

1. The soil no longer recieves shade from flora.
2. The soil no longer retains water or minerals due to the missing flora.
3. The soil no longer recieves diverse nutriunts from fauna.
4. A mineral or bacteria can become dominant in the soil.

It has been a wide taught fact here in europe.
Humans would then move to another patch of forest burn it down again and farm it again. On the old patch not much grows back due to ruined soil ecology. And whatever grows back is eaten by animals trying to survive and creates a harsh desert.

The aboriginals created a technique called firesticking to prevent forest fires and available land to farm on without harming the ecosystem too much.(They learned)
GSwift7
2.3 / 5 (3) Apr 13, 2012
Which means for the past 132 years the sea level rose an average of 3.53 times faster than the average in the previous 7000 years.

To me, that is statistically significant in terms of many sciences, meteorology, climatology, geology, etc.


Oh well, the article was available for free yesterday, but now it is paywalled. You can still see tiny versions of the graphs, but not really clear enough to read.

They have a graph of the rate of sea level change. What their data showed was that sea level had been going up and down over the past 6000 years. It reached a relative low around 1900 and stayed stable for a few decades, then it shot up really fast in the first half of the 1900's, then it stayed stable from the mid-1900's till now. So the rate of rise was really much higher than 1.5mm/yr, but the time period was much shorter. Such a change could be due to a shift in wind or tides rather than sea level. That's why they want to do more samples from other places in the region.
Lurker2358
3 / 5 (2) Apr 13, 2012
I really don't think the level of human-caused climate change 7000 years ago could have been anything other than negligible next to other factors. There simply weren't enough people around. It has only been since the start of the industrial age that human impact has been of great enough scale to cause a substantial amount of change to the global climate.


Did you ever read the Bible's description of the construction of the temple complex under David and Solomon?

That was just one project, and a monument that was relatively small compared to the construction projects of the Heliopolis or other monuments in Asia Minor, or the Pyramids in Egypt, or the Ziggurats in Babylon and Persia, etc.

Let's see...

"And he set threescore and ten thousand of them to be bearers of burdens, and fourscore thousand to be hewers in the mountain, and three thousand and six hundred overseers to set the people a work."

80,000 doing the cutting alone, and 3600 foremen!

70,000 helper/laborers
XQZME
2.3 / 5 (3) Apr 14, 2012
In 2005, the United Nations Environment Programme predicted that climate change would create 50 million climate refugees by 2010.
http://wattsupwit...attempt/

WASHINGTON STATE SEA LEVEL DROPPING.
http://www.appins..._usa.htm

Latest sea level graphs starting 1992.
http://sealevel.colorado.edu/

2500 years of Israeli sea levels one meter variation.
http://www.eureka...2610.php

8000 year sea level graph at end very little change n th last 2,000 years.
http://www.appins...evel.htm

Are these "scientists" are pandering for more research funds?
kaasinees
0.3 / 5 (24) Apr 14, 2012
In 2005, the United Nations Environment Programme predicted that climate change would create 50 million climate refugees by 2010.
http://wattsupwit...attempt/

Nearly 50 million americans are on food stamps.
If your government didnt introduce food stamps nearly 50 million americans would be fleeing/dying.
Their prediction was very accurate.

Latest sea level graphs starting 1992.
http://sealevel.colorado.edu/


Are you blind? The trend is going up not down. Sure a temporary dropdown in global sea level can be caused by many things, that doesnt mean that the ammount of ocean water decreased, it means that whatever was causing the water to drop is a temporary factor, and that is true if you look at the graph.

damn denilist idiots.