RISING SEAS: A new study shows that sea levels have been rising faster thanks to climate change
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Sea level is rising faster along the U.S. East Coast than it has for at least 2,000 years, according to new research.
The ocean began rising an average of 2.1 millimeters per year some time between 1865 and 1892 and hasn't stopped, the study concludes. The current rate of sea level rise is about 3.2 mm per year.
That trend, gleaned from muck collected in North Carolina salt marshes, is a direct consequence of increasing temperatures, said co-author Benjamin Horton, a coastal geologist at the University of Pennsylvania.
"We can see climate-related patterns," he said. "We can see our hypothesis that as temperature goes up, sea level goes up."
The reverse is also true, according to the research, which shows temperatures and sea levels rising and falling in lockstep for at least the last 1,000 years. The findings will be published online this week by the Proceedings of the National Academy of Sciences.
Peter Clark, a geologist at Oregon State University, said the new study represents a "significant advance" because it extends the record of sea level rise back two millennia, giving scientists a better context for current sea level rise.
"It's important to learn about past climate (and sea level) because we want to know how it varies naturally (i.e., when there was no possible human influence) so as to evaluate whether the current recent changes are unusual," he said in an email.
The new paper does "firmly establish" that current sea level rise is unprecedented for the recent past, said Ken Miller, a geologist at Rutgers University. The work was warmly received last year when the authors presented it at a sea level-rise workshop sponsored by the Intergovernmental Panel on Climate Change, he said.
Period of stability to A.D. 950
In addition to the recent sea level rise, the record pieced together by Horton's team shows a long period of stable sea level from 100 B.C. to A.D. 950. That marked the beginning of a warm period that lasted roughly four centuries, a time when seas rose 0.6 mm per year. Sea level then held steady, or slightly fell, until the late 19th century, when the current sea level spike began.
"When temperatures really rocketed as they did in the 20th century," Horton said, "our sea levels did the same."
Scientists have good measurements of recent sea level rise from a combination of tide gauges, which began collecting data in the early 20th century, and satellites, which started tracking sea level in 1992.
To go even further back in time and put recent conditions in context, the authors of the new study examined sediment samples from North Carolina salt marshes.
Those marshes are "an ideal natural laboratory," Horton said, because they are always slowly sinking and being rebuilt as tides wash in new sediment. That steady accumulation of muck traps tiny organisms called foraminifera, plant matter and other substances that form a natural record of sea level rise.
The scientists began decoding that record by mapping the distribution of different foraminifera species -- or "forams" -- at 10 North Carolina marsh sites.
A marsh is typically home to several species of forams, which each prefer slightly different conditions. Some thrive in the relatively fresh water found in areas that aren't often inundated by ocean tides, while others seek out a saltier brew.
Understanding which foram species were found in areas often overtopped by salt water and which weren't allowed scientists to construct a model they used to analyze sediment cores from two marshes and estimate sea level rise over time.
Peering back two millennia meant collecting cores 3 to 4 meters long. Extracting information about sea level required cutting those cores into 1-centimeter chunks and analyzing the foram fossils found in those chunks.
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10 Comments
Add CommentHow are they accounting for isostatic rebound and other elevation imapacting tectonic forces that could also effect sea-level? This is a complex interdiscipline area for study. This kind of ea level rise which has been going on since the end of the Ice Age,and which according to this report began accelerating in 1865, which is prior to the time when the large scale industrial use of petroleum became the hallmark of our modern era, so I'll be interested in reading what they think is going on, in all its complexity. Cheers.
Reply | Report Abuse | Link to thisAs a geologist I find this article more agenda driven based on 'science'. I caqn think of a half dozen reasons for the rise of ocean elevation. How do they isolate the rise in a particular location to 'climate change'?
Reply | Report Abuse | Link to thisClimatology continues to lose credibility as does the 'science' journalism of Scientific American.
@Geojelly Roll,
Reply | Report Abuse | Link to thisOK then what factor do you not think was addressed? In the publication of the Proceedings of the National Academies of Science they address such confounds as:
1. Glacial isostatic rebound.
2. Ocean Currents
3. Changes in the gravitational field (due to melting continental ice)
And so forth. Do you know what the "so forth's" are? Did you actually read the article before deciding to condemn the paper? Here is a link to the paper itself. It is a free download.
Climate related sea-level variations over the past two millennia: http://www.pnas.org/content/early/2011/06/13/1015619108.abstract
Want to debate the conclusion and methodology with author of the paper? Go here: 2000 Years of Sea Level (+update)
http://www.realclimate.org/index.php/archives/2011/06/2000-years-of-sea-level/
I look forward to a reasoned critique of the paper. Of course the one of the perquisites of a reasoned critique is that you have read the paper you critiqued.
Now I keep on seeing you claiming to be a geologist. So since you have made your supposed credentials central to the critique it is time that you share with us your peer reviewed work that relates to this topic.
geo has only one intent here, to try to sow the seeds of doubt in sciam readers. Well I doubt he is a geologist or any kind of scientist for that matter. I am more likely to believe he's a paid stooge for the Heritage Foundation. The only thing he forgot to add was that he is cancelling his subscription of ten years in protest. We've heard it all before.
Reply | Report Abuse | Link to thisWhy do you assume that because he has an opposing view to you,that he is a Stooge?
Reply | Report Abuse | Link to thisI am probably part of the conspiracy as well.
In this case it's a fairly well grounded assumption. If he were really a scientist, and really had a beef with what was written on science grounds he would have discussed it in that format rather than being intentionally vague. That's a rhetorical technique, not a dialogue.
Reply | Report Abuse | Link to thisHad he phrased it as simply an opinion without citing his position as a geologist and thereby commenting as an expert people would probably be a bit less suspicious. To put it bluntly, scientists are expected to provide evidence to support their opinions. This person claims to be a scientist and then engages in what amounts to obfuscating commentary. He makes no attempt to verify his credentials, cites no evidence to the contrary, and generally picks apart a paper on the basis of a short blurb about said paper in sciam.com without so much as providing a reason for his dissent that isn't addressed in the paper he apparently didn't read. Trent, asked for clarification and even, quite helpfully, provided the article and access to a venue in which this geologist (Of suspect provenance) could vent his spleen with the source. He is even giving the individual an opportunity to defend his statements. Odd, how he's made no attempt to do so.
Under the circumstances I'd say it's safe to say he's a stooge. Dissent, contrary to your apparent impression, is quite welcome in the sciences. In fact, peer review is part of the process for that very reason. Ideas are supposed to be questioned, but one does need to have reasons beyond just not liking them to back up one's point. Geojellyroll doesn't seem particularly inclined in dialogue or exchanging evidence. Which seems a bit unscientist like to me. I'm rather inclined to be suspicious of him as well under these circumstances.
@ Eboy,
Reply | Report Abuse | Link to thisI am not one for back slapping but that was one eloquent reply.
There is a superb reading list here for the scientifically literate layman
Reply | Report Abuse | Link to thishttp://suzukielders.wordpress.com/2011/06/01/climate-change-evidence-from-the-geological-record/
As a rabid anthropogenic global warming denier, I declare that this article is a load of...gurgle...bloop...glug...
Reply | Report Abuse | Link to thisHead for the hills, folks. The deniers are welcome to stay in the lowlands. Don't worry, we'll help you when the flood comes, but we may be unable to avoid a sardonic grin while doing it.
The East Coast shows no sea rise in a decade, but in fact quite a plunge:
Reply | Report Abuse | Link to thishttp://www.aviso.oceanobs.com/fileadmin/images/news/indic/msl/MSL_Map_J1_Global_IB_RWT_NoGIA_Adjust.png
World tide gauges show utterly no trend change in 150 years:
http://i.min.us/idFxzI.jpg