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
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.
This is 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
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.
Janet Lathrop | Eurek Alert!
In times of climate change: What a lake’s colour can tell about its condition
21.09.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)
Did marine sponges trigger the ‘Cambrian explosion’ through ‘ecosystem engineering’?
21.09.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
21.09.2017 | Physics and Astronomy
21.09.2017 | Life Sciences
21.09.2017 | Health and Medicine