Thermal windows, or the tolerable temperature ranges of some marine organisms, have evolved to be very narrow, possibly as a means to reduce the amount of energy and time spent on certain biological activities, such as feeding, growth, or reproduction. Scientists studying the impacts of climate change on North Sea Atlantic cod, a large fish with a narrow thermal range, attribute its recent northerly expansion into colder waters to climate change.
Scientists analyzing the seasonal oscillations of carbonate concentration and pH in the Southern Ocean have found a naturally occurring wintertime low in carbonate concentration that, when coupled with anthropogenic CO2 absorption, may cause further depletion in carbonate concentration, hastening ocean acidification. Their analyses led the scientists to predict an undersaturation of carbonate concentration in the Southern Ocean within just 30 years time, which is sooner than previously expected.
Until recently, models analyzing the effects of global warming on coral bleaching have been strictly based upon thermal stress projections, but a new study highlights the added impact of ocean acidification, yielding startling results.
Through experimental research, Dr. Ken Anthony led a team of scientists who found that the productivity and calcification rates of corals and important coral reef builders, crustose coralline algae, significantly decline under higher temperatures coupled with increased CO2 and high light exposure, suggesting that high CO2 levels may exacerbate coral bleaching events in warmer waters.
Using climate models, researchers from UK Met Office, the environmental and weather service for the UK, and Reading University have found that ocean salinity is increasing in waters of the mid-Atlantic, caused by a reduction in rainfall coupled with increased evaporation, both consequences of global warming.
The escalating salinity of the mid-Atlantic can only be explained by human-caused global climate change, the researchers concluded. What this means exactly for marine life and ecosystems appears uncertain, but such simulated climate models are helping scientists understand and project future oceanic reactions to global warming, such as the anticipation of a drier climate for southern Europe and the Mediterranean.
The latest report released by the National Oceanic and Atmospheric Administration (NOAA) affirms that as a result of the colossal loss of sea ice, autumn air temperature in the Arctic is a record 5º C (9°F) above normal, since the warming trend began in the mid-20th century.
As temperatures continue to rise due to human generated carbon dioxide emissions, white snow and ice give way to darker water and land beneath them. These darker surfaces absorb more heat than what would be reflected by the lighter snow and ice. This results in a positive feedback loop, causing more snow and sea ice to melt, exacerbating the Arctic warming.
Some marine animals may be able to cope with ocean acidification, but not without sacrifice.
A recent study revealed that one such creature, the brittlestar, which is capable of regenerating lost arms, is able to replace lost appendages more quickly in acidic seawater than in normal seawater because it increases calcification and metabolic rates to compensate for rising acidity.
But while arms sprouted faster than usual, they also sprouted thinner than usual. In brittlestars exposed to acidified seawater, muscle mass declined in both the already present, undamaged arms and in newly generated ones.
Cold-water corals (also known as deep-sea corals) are in as much danger from the corrosive effects of ocean acidification as those found in tropical waters.
Scientist James Orr recently found that population reductions in Arctic cold-water corals were analogous to those expected to occur in tropical corals. Orr and other scientists determined that by 2100, more than two-thirds of cold-water corals will be in waters corrosive to their calcium carbonate skeletons.
A new report looks at the effects of increased ocean acidity on how sound travels in seawater, which scientists have long suspected to be influenced by pH. The report found that drops in pH affect the ocean's chemical balance and consequently lower its sound absorption, especially to frequencies below 10 kilohertz (kHz). The researchers say that by the 1990s, the oceans absorbed 15% less sound than during the previous century, which will likely affect the communications of ocean wildlife as well as military operations, by making sound travel farther and increasing the ocean's ambient noise level. Already, scientists have discovered that blue whales, which normally communicate below1 kHz, have started calling at lower frequencies.
The volume of Arctic sea ice may be at its thinnest and most critical point in human history.
Despite recent headlines touting no new records for this year (it's looking like there will be slightly more sea ice this year than the 2007 record low) sea ice conditions overall are worse than ever before.
The Arctic sea ice is thinner and newer than it has been since scientists first set out to monitor sea ice extent in the 1970s. Since 1985, the Arctic has experienced a 56 percent decline in sea ice older than five years and the oldest ice has already vanished.
Not breaking records in this case is a good thing; however, with such a persistent yearly loss of older, thicker sea ice, don't be fooled, trends in the Arctic are dire.
For more on climate change, see http://oceana.org/climate.
Greenland holds the world's second largest amount of ice, second only to Antarctica. Ice covers four-fifths of Greenland's surface and reaches depths of almost two miles at its thickest spots. The island's large glaciers get the most attention and are attentively monitored while the smaller glaciers go largely unobserved. But a new study reports that it's actually these small coastal glaciers that are more significant, in terms of melting and contribution to sea level rise, than the larger glaciers.
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