From the University of Massachusetts at Amherst and the department of melted evidence, comes this interesting story about the last ice age.
Icebergs once drifted to Florida, new climate model suggests
The first study to show that when the large ice sheet over North America known as the Laurentide ice sheet began to melt, icebergs calved into the sea around Hudson Bay and would have periodically drifted along the east coast as far south as Miami
AMHERST, Mass. – Using a first-of-its-kind, high-resolution numerical model to describe ocean circulation during the last ice age about 21,000 year ago, oceanographer Alan Condron of the University of Massachusetts Amherst has shown that icebergs and meltwater from the North American ice sheet would have regularly reached South Carolina and even southern Florida. The models are supported by the discovery of iceberg scour marks on the sea floor along the entire continental shelf.
Such a view of past meltwater and iceberg movement implies that the mechanisms of abrupt climate change are more complex than previously thought, Condron says. “Our study is the first to show that when the large ice sheet over North America known as the Laurentide ice sheet began to melt, icebergs calved into the sea around Hudson Bay and would have periodically drifted along the east coast of the United States as far south as Miami and the Bahamas in the Caribbean, a distance of more than 3,100 miles, about 5,000 kilometers.”
His work, conducted with Jenna Hill of Coastal Carolina University, is described in the current advance online issue of Nature Geosciences. “Determining how far south of the subpolar gyre icebergs and meltwater penetrated is vital for understanding the sensitivity of North Atlantic Deep Water formation and climate to past changes in high-latitude freshwater runoff,” the authors say.
Hill analyzed high-resolution images of the sea floor from Cape Hatteras to Florida and identified about 400 scour marks on the seabed that were formed by enormous icebergs plowing through mud on the sea floor. These characteristic grooves and pits were formed as icebergs moved into shallower water and their keels bumped and scraped along the ocean floor.
“The depth of the scours tells us that icebergs drifting to southern Florida were at least 1,000 feet, or 300 meters thick,” says Condron. “This is enormous. Such icebergs are only found off the coast of Greenland today.”
To investigate how icebergs might have drifted as far south as Florida, Condron simulated the release of a series of glacial meltwater floods in his high-resolution ocean circulation model at four different levels for two locations, Hudson Bay and the Gulf of St. Lawrence.
Condron reports, “In order for icebergs to drift to Florida, our glacial ocean circulation model tells us that enormous volumes of meltwater, similar to a catastrophic glacial lake outburst flood, must have been discharging into the ocean from the Laurentide ice sheet, from either Hudson Bay or the Gulf of St. Lawrence.”
Further, during these large meltwater flood events, the surface ocean current off the coast of Florida would have undergone a complete, 180-degree flip in direction, so that the warm, northward flowing Gulf Stream would have been replaced by a cold, southward flowing current, he adds.
As a result, waters off the coast of Florida would have been only a few degrees above freezing. Such events would have led to the sudden appearance of massive icebergs along the east coast of the United States all the way to Florida Keys, Condron points out. These events would have been abrupt and short-lived, probably less than a year, he notes.
“This new research shows that much of the meltwater from the Greenland ice sheet may be redistributed by narrow coastal currents and circulate through subtropical regions prior to reaching the subpolar ocean. It’s a more complicated picture than we believed before,” Condron says. He and Hill say that future research on mechanisms of abrupt climate change should take into account coastal boundary currents in redistributing ice sheet runoff and subpolar fresh water.
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I guess I’d be pretty surprised had icebergs not regularly made it to Florida. In 1926 one made it to to within 150 nm of Bermuda.
Indeed, not surprising. During Heinrich Events, armadas of icebergs make it to Portugal, affecting circulation even in the Med:
http://onlinelibrary.wiley.com/doi/10.1029/2004PA001051/pdf
Thanks. Interesting paper.
The fact that dramatic changes in the Atlantic may cause dramatic changes in the Mediterranean is suggested by cores into the bottom of the Mediterranean, which show the layers changing to black ooze at times. (New vocabulary word: “Sapropels”.)
http://www.clas.ufl.edu/users/jmjaeger/gly4552/Med_sapropels_MArGeol_review.pdf
Bermuda isn’t close to Florida.
http://www.navcen.uscg.gov/?pageName=iipWhatIsTheExtremeRangeOfIcebergLocations
Some notable iceberg sightings of the past 131 years (during the Modern Warm Period):
In 1926, the southernmost known iceberg (a growler) reached 30-20 N, 62-32 W (about 150 nm from Bermuda).
In 1883, a growler was located about 200 nm south of the Azores.
In 1912, a growler was seen about 75 nm east of Chesapeake Bay, USA.
With colder water & air temperatures during the LIA, icebergs might have survived with some regularity south of 30 degrees N.
PS: No, Bermuda isn’t very close to FL, but the 1926 growler was sighted in the same latitude as Jacksonville.
To be fair, growlers aren’t really considered icebergs. It goes growlers (size of a car), bergy bits (size of a house) and then icebergs. And yeah, during the last Ice Age I’d wager icebergs got considerably south of Florida.
Growlers are considered icebergs, just little. That actually makes them dangerous, as harder to spot.
No but today the closest tidewater glaciers to Florida are in Greenland while during the LGM they were in New England.
Growlers are indeed “small icebergs” and must be distinguished from lumps of sea-ice. Growlers consist of glacial ice which is very hard and they can be quite dangerous. The “Lindblad Explorer” sank in Antarctica after hitting a growler.
tty:
The nomenclature isn’t perfect because “iceberg” means two things, ie a big iceberg, & icebergs in general, ie chunks of or melted down remains of formerly glacier or ice sheet ice, whether full icebergs, bergy bits or growlers.
Don’t know if the ice sheet edge in NY & NJ met tidewater or not at the LGM, but of course you’re right in the area of New England, where the Georges Bank was exposed, as were the Grand Banks of Newfoundland, & Flemish Cap, which was an island.
ok time for a different thought new mechanism to move icebergs to Florida couple facts to start with last glacial period depressed the crust inward to the point where Florida was twice as wide as today and not because of ocean drop but because the crust bulged up under Florida. push the crust downward and the magma pool underneath will wear the crust thin example the Hawaiian island chain formed by burning thru the crust now put that hot spot under a five to ten thousand foot ice cap on a nonmoving crust and the hot spot would melt the ice from bottom up and the center out giving us a huge fresh water ocean above sea level until the ice melt weakens the ice dam to the point wear several collapses occur at once with huge ice burgs flowing outward in all directions at which time the crust would return to its beginning state dumping the rest of the stored water back into the ocean and im willing to bet that 95% of man lived within 50 feet of ocean level just like today duh and a lot of people died in a world wide tsunami at the end of the last ice age thought if the water released slowly the huge fresh cold water release into the warm salty water would have caused huge rain storms from the energy convergence helping to weaken a collapse of the dam in several locations now please tell me why im wrong just looking for a better world lets hope for another thousand years before the next glacial period
“[…] next glacial period”
Nice to see a period at the end.
Oops. sorry, Jani. I made a flippant comment without helping you out a bit. One little fly in your hypothesis is that the rise in Florida isn’t attributed to isostatic rebound from the retreat of the glaciers, but rather that the limestone bed of Florida is getting lighter as rainwater dissolves some of the limestone. The rise is attributed to Florida floating higher on the mantle.
I’m not thrilled with the source at this link, but it plainly discusses the process as do other, less reader-friendly links.
http://news.discovery.com/earth/global-warming/florida-limestone-swiss-cheese.htm
I like the thought of rain storms hitting the ice sheet at many different places. I’ll have to cogitate on that one.
I think it makes sense that isostatic rebound in Florida might be prompted by the limestone leeching out, and becoming filled with caves. It is interesting that the dates of the three levels of elevation in Florida roughly match up with ice-ages.
However the rate of uplift in these cases seems to be very slow, on the order of 0.047 millimeters per year. The sea level rose much faster than that at the end of the ice age.
Therefore I do not think this is a case of “either-or”. It seems to be a case involving slow isostatic rebound and more rapid sea-level rises (and falls) due to ice-ages.
Keep in mind that, while the Florida Trail limestone has been uplifted 250 feet, it dates from 1.44 million years ago. During that time the oceans have gone up and down 300 feet multiple times.
(Be wary of the words “geologically recent” in such news items.)
This is a joke?
I doubt it. It is called, “Thinking outside the box”, and I enjoy it.
I have done a bit of it myself, in order to explain some of the lore involving the abrupt end of Atlantis. While it is generally assumed that isostatic rebound is a very gradual and slow process, I see no reason to never consider such uplift occurring rapidly, even as a jolt, especially when one considers the vast weight removed by “meltwater flood events.” Such jolts might cause further “catastrophic glacial lake outburst floods.”
Even if it is not science, it might be a good premise for science fiction.
Then add in a comet hitting the ice-sheet.
Double oops; Juli, not Jani. (I am blind in both eyes and my eyes do play tricks. Apologies.)
Another item, that I don’t see mentioned, is cold meltwaters coming down the Mississippi River valley into the Gulf of Mexico. The map doesn’t show any blue off the west coast of Florida. Was this even considered by the model?
Walter, that other item you don’t see mentioned; this image shows how the Appalachians would split the flow of the melt waters. It appears to me that the melt from the central portion of the ice sheet would be funneled a little further west of Florida rather than close by Florida’s west coast.
http://www.cosmographicresearch.org/Images/glacial_maximum_map2.jpg
Of course you’re right that the Gulf basin would be hit with of a lot of fresh water. I’m not clear whether or not it mattered in their model, though. Maybe the next study is to look for scour marks off the west coast ;o)
Need more grant money, eh?
(Caleb October 14, 2014 at 12:59 am)
Caleb,
Jani has Florida rising due to the weight of the glaciers mid-continent. Florida should be subsiding due to the weight being removed. It’s rising now.
If I read that one long sentence correctly, the ice bergs were sent willy-nilly across the continent in all directions as ice dams collapsed. If I recall correctly, there’s a mountain chain between the termini of the past few glaciers that would tend to block Jani’s ice bergs from floating on down to Florida. That, and I don’t recall any reports of ice berg keel marks down through Georgia. Jani’s idea just won’t float, but it was an interesting sentence.
If one looks at a graphic of the Hudson Canyon then one can easily see the eroded channel of the Hudson River from where it exits the NYC area at the western tip of Long Island and flowed across the Inner Shelf and then down the steep 120+- meters (360+ feet) face of the Outer Shelf and thus creating the Hudson Canyon.
For the outflow of the Hudson River to have caused the massive erosion resulting in the formation of the Hudson Canyon then the sea levels at the time had to have been 200 to 250 meters lower than present …. and there had to have been a large volume of fast flowing “meltwater” flowing through said channel.
And iffen, as the experts claim, the Late Wisconsin Glacier (LWG) covered much of NYC and Long Island with ice up to or greater than 3,300 feet thick at 18,000 years BP then the southern edge of said LWG had to have extended far out overtop the Inner Shelf where the calving of said glacier would have occurred. Icebergs don’t normally calve-off over dry ground.
Samuel C. Cougar:
“200 to 250 meters”
Interesting observation as that is about a hundred meters, more or less, below SL at glacial max. This implies sub-sea scour formed the lower part of the channel. How to explain this? Perhaps someone has presented a plausible explanation.
@ur momisugly mpainter: October 14, 2014 at 9:34 am
“Interesting observation as that is about a hundred meters, more or less, below SL at glacial max. This implies sub-sea scour formed the lower part of the channel”.
—————-
There is a “plausible explanation” for your quandary concerning the sea level variance of 120 meters verses the 250 meters as stipulated in my above post.
The 120m figure was in reference to the vertical height of the Outer Shelf (200m – 80m = 120m), ….. and the 250m was in reference to the vertical height as measured from the very bottom of the Hudson Canyon to present day sea level at the “shoreline” of Long Island, to wit:
http://www.nefsc.noaa.gov/press_release/2010/SciSpot/SS1003/HudCanFinderMap.jpg
Thus I will assume that you confused my stated 120m cliff-height figure with the claimed 120m rise in sea levels during the Post Glacial Sea Level Rise that occurred during the pre-Holocene Period as stated on this “meltwater” proxy graph, to wit:
http://www.climate.org/images/postglacial-sea-level-rise.png
If that 120m proxy figure is correct then the actual sea level during the most recent “glacial maximum” (Ice Age) was located at 40+ meters below the top edge of the Outer Shelf. And the outflow of the Hudson River during said pre-Holocene Period would have caused additional erosion of the Hudson Canyon down to said “40 meter mark” on the Outer Shelf, …. but not below said “mark”.
But there have been several Ice Ages during earth’s history, also 1 or 2 “Snowball” earth Periods, which would explain why the erosion of the Hudson Canyon extends below the aforesaid “40 meter mark” down to 250+- meters below the current sea level.
If you use Google “Images” and search for “Hudson Canyon” it will display quite a few different graphics that will better define the erosion of the continental shelf that has occurred during the “glacial maximums” of past millenniums.
“””””…..“The depth of the scours tells us that icebergs drifting to southern Florida were at least 1,000 feet, or 300 meters thick,” says Condron. “This is enormous. Such icebergs are only found off the coast of Greenland today.”…..”””””
I somehow doubt that is true. Icebergs of that size routinely break off from Antarctica, and they can also sail all the way up to New Zealand.
Back in 2006, when I was down there touring the South Island, there was a whacking great iceberg off the coast and I could have booked a helicopter ride out to land in it.
I decided, that I wanted to remain in one piece for the time being, so I didn’t go, but lots of people did.
But those sea floor gouge marks, look rather weird. I wonder why modern ocean currents haven’t filled them in.
I also question the above quoted claim of a “1,000 feet, or 300 meters thick” iceberg simply because one can not be sure at what “time” during the pre-Holocene Post Glacial Sea Level Rise (see above graph) that said icebergs calved off of the LW glacier.
Is not said “scour” marks a function of …. iceberg mass + iceberg momentum + sea level height?