Icebergs once drifted to Florida, new climate model suggests

October 12, 2014
As icebergs drifted south along the coast their keels plowed into shoaling areas on the seafloor, creating the characteristic grooves shown here in a seafloor bathymetry image from offshore of South Carolina.

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 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 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 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."

A map showing the pathway taken by icebergs from Hudson Bay, Canada, to Florida. The blue colors (behind the arrows) are an actual snapshot from the authors' high resolution model showing how much less salty the water is than normal. The more blue the color the less salty it is than normal. In this case, blue all the way along the coast shows that very fresh, cold waters are flowing along the entire east coast from Hudson Bay to Florida. Credit: UMass Amherst

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 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 should take into account coastal boundary currents in redistributing runoff and subpolar fresh water.

Explore further: New, high-resolution global ocean circulation models identify trigger for Earth's last big freeze

More information: Nature Geosciences, dx.doi.org/10.1038/ngeo2267

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12 comments

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Shootist
1.4 / 5 (11) Oct 12, 2014
Warm climate is better for humans and other growing things.
mbee1
1.7 / 5 (11) Oct 12, 2014
Lets take these statements and models as being true. The CO2 content of the air was about half todays level. Think about it freezing ocean water off Florida, icebergs in Miami if Miami was on the other side of Florida, yet somehow all that cold water, all those icebergs disappeared without a large CO2 rise. Something else melted tens of thousands of cubic miles of ice covering north america. Yet not a single AGW supporter will admit that CO2 was not the agent of change nor do they suggest any other agent of change. Why is that? Because they know the only agent of change was solar gain and if they admit that than their whole redistribute the wealth hysteria goes down the drain.
runrig
4 / 5 (12) Oct 12, 2014
Warm climate is better for humans and other growing things.

Not when said warm climate will enviably melt polar ice.
You say warm, yes? I assume you mean globally, as that is what is at issue. So the Arctic will therefore warm more than the rest of the planet. Yes? Unarguable my friend.
So what is the consequence? .... Err, ice melts in a warm climate.
And what does melted ice become?.. Err water.... Which drains into?.....The ocean.... And raising it's level.
And where are most of the major cities in the world?
Mr selfish shootist, wot you think the slowing of the PJS will do in regard to pushing rain bearing storms over continents?
You have no idea, not even the slightest inkling of the bollocks you talk.
FFS f^^**g squared wot a prat you are.
runrig
3.9 / 5 (12) Oct 12, 2014
Lets take these statements and models as being true. The CO2 content of the air was about half todays level. Think about it freezing ocean water off Florida, icebergs in Miami if Miami was on the other side of Florida, yet somehow all that cold water, all those icebergs disappeared without a large CO2 rise. Something else melted tens of thousands of cubic miles of ice covering north america. Yet not a single AGW supporter will admit that CO2 was not the agent of change nor do they suggest any other agent of change. Why is that? Because they know the only agent of change was solar gain and if they admit that than their whole redistribute the wealth hysteria goes down the drain.

The "agent of change" was the Earth's orbit. Of course! Look up 'Milankovitch cycles' and dispel your appalling ignorance. CO2 was then out gassed form the oceans/land, leading to a +ve feedback.

Canute
5 / 5 (1) Oct 12, 2014
When the ice dams of the great lakes Aggassiz and Missoula burst, did they not produce a rush of fresh water flowing at 10 cubic MILES per hour- more than the current flow rate of all rivers of the world combined. Surely this would have given a few icebergs a push south. Such an influx of freshwater would also impact the thermohaline layer which in turn would change the climate significantly. Currently the artic ice is melting fast and despite increasing sea ice in the Antarctic, the western ice sheet is melting quickly possibly due to having active volcanoes underneath. Is anyone modelling the potentials impact of these events on current climate change?
Rick_Geo
1.6 / 5 (7) Oct 12, 2014
The media tries to generate panic by stating that inhabited coral atolls in the Pacific (and the Florida Keys) are in danger of rising sea level. In Geology 101 you learn that coral only grows underwater. Therefore, sea level has been higher in the past and the Earth has been warmer. Since the sea level dropped, exposing the reefs, they have been subject to continuous erosion. As runrig correctly stated, the Milankovitch cycles are the main driver of climate change.
Returners
1 / 5 (5) Oct 18, 2014
If you made like a terawatt worth of hydro power in the Gulf Stream, you'd slow down it's northward progression a bit, and this would allow more sea ice to form in the Arctic year round. It'd be win-win since you'd offset a massive amount of pollution, eventually, and it would directly contribute to positive albedo change.

Turbulence produced by the system would potentially pull up cold water from the depths, potentially improving the environment for ice to form as well.

Energy is pulled directly from the ocean, used in our machines, and waste heat is released on land. It is easier for waste heat on land to escape back to space than from the original eat in the water.

Thus the entire system would be literally a global air conditioning system, and produce enormous amounts of useable electric power all at the same time.
TheGhostofOtto1923
4 / 5 (4) Oct 18, 2014
If you made like a terawatt worth of hydro power in the Gulf Stream, you'd slow down it's northward progression a bit, and this would allow more sea ice to form in the Arctic year round
Hey maybe you could combine this with the equally asinine idea of building millions of oceangoing solar barges.

Please calculate how much obstruction would be required to slow down the gulf stream to the extent that it would affect ice formation in the arctic, assuming that such an obstruction would affect ice formation at all.

And please also confine your calcs to 4 or 5 posts which seems to be the average number you need to prove astrophysicists and cosmologists wrong about things like planetary migration and dark matter distribution.
Returners
1 / 5 (3) Oct 18, 2014
Ghost:

A terawatt of heat energy removed from the ocean across an entire year is enough to freeze approximately 80 cubic kilometers of water to ice, and this doesn't count the potential of stirring colder water from the depths to the surface via turbulence.

Some years in the decline of sea ice, the volume only shrank by about 100cu km in the first place, and some years it increases. So if you figur adding 80cu km per year, or offsetting 80cu km per year for years or decades (until an asymptote is hit) then it would be a pretty big effect.

Place under water turbines in the Florida Straits, Bahamas, and up the Florida Coast.

Water turbines are about 20% efficient.

You know, I bet we can ask these guys who did this modeling to try modeling that scenario for like a 20 year or 100 time span and see how big of a difference that would make in direct and indirect benefits.

the energy itself is an 80cu km of ice difference...per year.
TheGhostofOtto1923
4 / 5 (4) Oct 18, 2014
Ask these guys to do modelling
Why, when you can do it all in your head? For your next post please quantify the amount of turbines you would need to install in the gulf stream to freeze 80 ckm of sea water. Per year. One more post oughta do it. I would guess millions and millions but then I would be guessing.
TheGhostofOtto1923
3.7 / 5 (3) Oct 18, 2014
Some statistics to consider... The average speed of the Gulf Stream is only 4 mph, which slows to 1 mph in the north. And the volume is 4 billion cubic meters per second, greater than all the rivers in the world combined.

So you've got to calculate how this amount of water actually affects arctic ice formation. I would guess that your terawatt quantity is somewhat low. But I would only be guessing.
TheGhostofOtto1923
3 / 5 (2) Oct 18, 2014
Finally Lrrkrrr you would have to figure just how much of that energy differential gets mitigated across the millions of square miles of Atlantic water that the gulf stream interacts with as it travels north, and how much (or little) is left to interact with arctic waters when it reaches the vicinity, and how the arctic currents distribute whatever energy the arctic acquires from the Gulf Stream. It is not a bathtub you know.

Yes, if I were dumb enough to guess at all I would guess that a terawatt is a paltry amount indeed.

So that's 3 posts. Have at it.

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