Circulation on EARTH Magazine

Ocean circulation change suffocating Gulf of St. Lawrence

Fri, 21 Dec 2018 11:03:00 -0500

Research suggests that the Gulf Stream is shifting to the north, such that it's impinging on the flow of the Labrador Current near the Tail of the Grand Banks and reducing the supply of well-oxygenated water to the Gulf of St. Lawrence. Credit: K. Cantner, AGI.

Estuaries are among the most nutrient-rich and biologically productive areas of the ocean, and the Gulf of St. Lawrence, where freshwater from the Great Lakes and the St. Lawrence River meets the salty Atlantic Ocean in eastern Canada, is the largest estuary in the world. But the biodiversity and long-thriving fisheries of the Gulf of St. Lawrence could be threatened by declines in oxygen levels over the last half century. A new study suggests that a large-scale shift in Atlantic Ocean circulation is dumping warmer, oxygen-poor water into the gulf.

Disrupting the deep: Ocean warming reaches the abyss

Thu, 08 Mar 2018 11:29:52 -0500

SOCCUM Project, Hannah Zanowski, CC BY 2.0

Seventy-one percent of our planet is covered by ocean, and these basins contain 97 percent of Earth’s near-surface water. The ocean lies at the heart of the global climate system, shaping all parts of our environment, even in the deepest continental interiors. So as the ocean goes, so goes the planet — and the ocean is warming.

How the Arctic became salty

Thu, 14 Sep 2017 12:48:13 -0400

During the Eocene, the Arctic Ocean was a giant freshwater lake fed by rivers and ice melt. Today, it's salty and ice-covered much of the year. Credit: NASA.

The Arctic Ocean hasn’t always been as salty as other oceans. In the Eocene, between 56 million and 34 million years ago, the water surrounding the North Pole — freshened by melt from sea ice and river runoff — was cut off from the Atlantic and Pacific oceans by land bridges. At some point, plate tectonic processes opened the North Atlantic, submerging the land bridges and allowing saltwater to pour into the Arctic, but the timing and details of these events are largely unknown. New research suggests a tipping point may have been reached as one particular land bridge submerged far enough below the ocean surface.

Ice (Re)Cap: May 2017

Wed, 19 Apr 2017 20:09:22 -0400

Bucking the global trend of glacial retreat, Franz Josef Glacier in New Zealand's Southern Alps advanced for much of the period between 1983 and 2008. Credit: Wendy Mann, CC BY 2.0.

From Antarctica to the Arctic; from polar caps, permafrost and glaciers to ocean-rafted sea ice; and from burly bears to cold-loving microbes, fascinating science is found in every nook and crevasse of Earth’s cryosphere, and new findings are announced often. Here are a few of the latest updates.

A new — and more toxic — normal? Harmful algal blooms find new habitats in changing oceans

Fri, 13 Jan 2017 13:06:09 -0500

An Envisat image of a phytoplankton bloom in the South Atlantic Ocean east of the Falkland Islands on Dec. 2, 2011. Chlorophyll pigment detected by ocean-color sensors on Earth-observing satellites can help identify species in algal blooms and their toxicity. Credit: ESA.

In May 2015, a seizure-wracked sea lion hauled itself ashore on a beach in southern Washington. Testing confirmed it was suffering from domoic acid poisoning, an illness that causes disorientation, seizures and sometimes death that stems from the consumption of fish or shellfish contaminated by a toxic species of algae called Pseudo-nitzschia. To the south, in warm California waters where localized toxic blooms of Pseudo-nitzschia are a near-annual occurrence, sea lion illnesses caused by exposure to domoic acid are common — however, this was a first in Washington. The sick sea lion was euthanized, but its stranding in Washington alerted coastal communities to the massive algae bloom that was engulfing coastal waters from Santa Barbara, Calif., all the way to British Columbia.

Atmosphere, more than ocean, might drive Atlantic climate variation

Fri, 08 Jan 2016 08:10:00 -0500

Hurricane Isabel was photographed from the International Space Station in 2003, during the most recent warm phase of the Atlantic Multidecadal Oscillation (AMO). The AMO, which seems to affect the frequency of tropical storms, may be more affected by atmospheric circulation than by the ocean. Credit: NASA.

Atmospheric, not oceanic, circulation may be the main driver of climate variations over the North Atlantic Ocean, potentially complicating future hurricane and drought predictions, according to the authors of a new study.

Southbound icebergs off the hook for ice-age cooling

Fri, 17 Jul 2015 09:27:00 -0400

A new study suggests that southbound icebergs probably arrived too late to be the trigger for Pleistocene cooling events in the North Atlantic. Credit: ©kaet44, CC BY 2.0.

During the Late Pleistocene, changes in North Atlantic Ocean circulation triggered abrupt changes in global climate: In some locations in the Northern Hemisphere, average temperatures dropped by as much as 10 degrees Celsius within a few decades. Scientists have long thought that freshwater from melting icebergs traveling south from the Arctic may have instigated the circulation shifts that contributed to cooling feedback loops. But now, scientists looking at seafloor sediments collected near Iceland have found that pulses of icebergs typically arrived after the onset of cooling episodes, too late to be primary drivers of climate change.

Hydrogen chloride on the rise in Northern Hemisphere skies

Mon, 08 Jun 2015 12:44:20 -0400

Concentrations of hydrochloric acid measured over the South Pole on Aug. 13, 2004 (warm colors indicate higher concentrations). Credit: NASA/Goddard Space Flight Center.

Levels of the atmospheric pollutant hydrogen chloride have increased substantially in the lower stratosphere over the Northern Hemisphere since 2007, according to a new study. The increase, however, is not due to an influx of chlorine, but rather to a side effect of the recent slowing of stratospheric circulation that was first reported in 2005.

Ocean waves explain which La Niña events will linger

Fri, 18 Jul 2014 18:00:40 -0400

El Niño years are characterized by warm conditions in the eastern tropical Pacific while in La Niña years, like 2007 (shown here), the tropical Pacific is cool. Credit: NASA.

Many La Niña events last just one season, but historical records reveal that nearly half linger for two years or more, a phenomenon scientists have long struggled to explain. Now, new research has identified a potential mechanism behind such enduring La Niñas that may provide a blueprint for the kinds of long-range predictions needed to mitigate the economic impacts of associated events like the devastating Texas drought.

Voyage to the plastic vortex

Thu, 05 Jan 2012 06:41:58 -0500

SEAPLEX researchers examine a stuffed toy dog after it was collected along with ghost net debris on Aug. 15, 2009. 2009 Scripps Institution of Oceanography Photo credit: J. Leichter

Out in the middle of the northern Pacific Ocean, a giant floating mess of plastic debris is drifting and bobbing among the waves. Scientists call this expanse of litter, which stretches for hundreds of kilometers across open sea, the Great Pacific Garbage Patch. But before last summer, there was little information about how large the patch really is, what types of debris are out there and what kind of impact it is having on ocean life.