Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Northwest Atlantic Ocean ecosystems experiencing large climate-related changes

26.02.2007
Research shows links between collapse of fisheries and bottom-living species

Ecosystems along the continental shelf waters of the Northwest Atlantic Ocean--from the Labrador Sea south of Greenland all the way to North Carolina--are experiencing large, rapid changes, report oceanographers funded by the National Science Foundation (NSF) in the Feb. 23, 2007, issue of the journal Science.

While some scientists have pointed to the decline of cod from overfishing as the main reason for the shifting ecosystems, the paper emphasizes that climate change is also playing a big role.

"It is becoming increasingly clear that Northwest Atlantic ecosystems are being affected by climate forcing from the bottom up and overfishing from the top down," said Charles Greene, an oceanographer at Cornell University in Ithaca, N.Y, and lead author of the Science paper. "Predicting the fate of these ecosystems will be one of oceanography's grand challenges for the 21st century."

Most scientists believe humans are warming the planet by burning fossil fuels and changing land surfaces. Early signs of this warming have appeared in the Arctic. Since the late 1980s, scientists have noticed that pulses of fresh water from increased precipitation and melting of ice on land and sea in the Arctic have flowed into the North Atlantic Ocean and made the water less salty.

At the same time, climate-driven shifts in Arctic wind patterns have redirected ocean currents. The combination of these processes has led to a freshening of the seawater along the North Atlantic shelf.

"Long time-series measurements, as well as research on large-scale ocean processes, are the key to improving our understanding of ecosystem shifts," says Mary Elena-Carr, program director in NSF's biological oceanography program. "This study brings together the important components: the atmosphere, freshwater flow, changes in currents and biological responses, all necessary to predicting future ecosystem responses to climate change."

Under normal conditions in summer months a warmer, less salty layer of water floats on the surface (warmer, less salty water is also less dense and lighter). This surface layer is known as a "mixed" layer, because wind-driven turbulence mixes the water and creates a uniform temperature, salinity and density to depths that can range from 25 to 200 meters.

Similar to the flow of heating and cooling wax in a lava lamp, when the air temperature cools during autumn, temperature and density differences lessen between the surface mixed layer and the cooler, saltier waters below. As the density differences get smaller, mixing between the layers typically increases and the surface mixed layer deepens.

But Greene cites recent scientific studies that reveal the influx of fresh water from Arctic climate change is keeping the mixed layer buoyant, inhibiting its rapid deepening during autumn. A gradual rather than rapid deepening of the mixed layer has impacted the seasonal cycles of phytoplankton (tiny floating plants), zooplankton (tiny animals like copepods) and fish populations that live near the surface.

Normally, when the mixed layer deepens rapidly during autumn, phytoplankton numbers decline because they spend less time near the surface where they are exposed to the light necessary for growth. But with the mixed layer remaining relatively shallow, phytoplankton populations stay abundant throughout the fall. In turn, zooplankton that feed on phytoplankton have increased in number during the fall through the early winter. Herring populations also rose during the 1990s, which some scientists suspect may be because of more abundant zooplankton to feed on.

Greene's paper also cites a link between the collapse of cod fisheries in the early 1990s and an increase in bottom-living species such as snow crabs and shrimp, which cod prey upon. Without cod, other animals that live in the water column and feed on zooplankton, including herring, may have increased.

While the herring story is still unclear, the authors contend that the crash of cod populations does not explain why phytoplankton and zooplankton populations at the base of the food chain have risen during autumn.

"We suggest that, with or without the collapse of cod, a bottom-up, climate-driven regime shift would have taken place in the Northwest Atlantic during the 1990s," Greene said.

Cheryl Dybas | EurekAlert!
Further information:
http://www.nsf.gov

More articles from Ecology, The Environment and Conservation:

nachricht Successful calculation of human and natural influence on cloud formation
04.11.2016 | Goethe-Universität Frankfurt am Main

nachricht Invasive Insects Cost the World Billions Per Year
04.10.2016 | University of Adelaide

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Closing the carbon loop

08.12.2016 | Life Sciences

Applicability of dynamic facilitation theory to binary hard disk systems

08.12.2016 | Physics and Astronomy

Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D

08.12.2016 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>