Oceanography

Groundwater extraction and other land water contribute about three times less to sea level rise than previous estimates, according to a new study. Sea level has risen an estimated average 1.7 mm per year over the 20th and the early 21st century, and concerns are that will increase uif climate change further warms the planet.

Researchers have the rising seas to a combination of factors including melting ice caps and glaciers, thermal expansion (water expands as it gets warmer), and the extraction of groundwater for human use. Land water contributions are small in comparison to the contribution of ice melt and thermal expansion, yet they have been increasing, leading to concerns that this could exacerbate the problem of sea level rise caused by climate change.


Coral reefs, the world's most productive and diverse marine ecosystems, rely on a recycling program to stay healthy: The corals and algae that form the base of the reef's food web release a variety of nutrients that support a complex and efficient food chain.

But when this system gets out of whack, the cycle breaks down and endangers the coral reef's health, and a new paper in Nature Microbiology explores how a process known as "microbialization" destroys links in this delicate food chain.


Vanishing Arctic sea ice, dogged weather systems over Greenland, far-flung surface ice melting on the massive island - these trends and global sea-level rise are linked by climate change, according to a new paper.

During Greenland summers, melting Arctic sea ice favors stronger and more frequent "blocking-high" pressure systems, which spin clockwise, stay largely in place and can block cold, dry Canadian air from reaching the island. The highs tend to enhance the flow of warm, moist air over Greenland, contributing to increased extreme heat events and surface ice melting, according to the computer models and field measurements 
in the Journal of Climate.


Current climate models are too simplistic to really account for all of the factors in climate in the present, much less predict the future, but they are being used by policy makers to anticipate the effects of greenhouse gases as far out as a hundred years so it is important they gradually converge on accuracy before too much money is spent.

Today, at the Microbiology Society's Annual Conference, scientists discussed one missing piece of the puzzle in computer simulations - Arctic microbes that are increasing the rate at which glaciers melt.


Scientists have developed a mathematical model to derive the probability of extreme waves. This model uses multi-point statistics, the joint statistics of multiple points in time or space, to predict how likely extreme waves are.

The results, published today, Friday 11 March, in the New Journal of Physics, demonstrate that evolution of these probabilities obey a well-known function, greatly reducing the complexity of the results.
"It's common in science and engineering to consider noise and fluctuations as something we need to avoid or eliminate in order to gain the best results" explains Matthias Wächter, an author on the paper. "For us, understanding noise and fluctuations is helpful for understanding complex systems."


While there is speculation and numerical estimates about what might happen to Antarctica's nation-sized Ross Ice Shelf in a warming climate,  oceanographers have a good idea of what happened to a 100,000-square-mile section within 1,500 years after the last Ice Age ended. 

The Ross Ice Shelf is a vast floating extension of the West Antarctic Ice Sheet, about the size of France,  and the world's largest ice shelf. But it was once much larger, extending farther north and covering the entire Ross Sea.  The present Ross Ice Shelf is about 500 miles wide and several hundred feet thick. Because the ice shelf is already floating, its breakup and melting would not pose a risk of raising global sea level.  


Ancient records tell us that the intrepid Viking seafarers who discovered Iceland, Greenland and eventually North America navigated using landmarks, birds and whales, and little else. There’s little doubt that Viking sailors would also have used the positions of stars at night and the sun during the daytime, and archaeologists have discovered what appears to be a kind of Viking navigational sundial.

Some scientists have been so convinced that iron fertilization will help mitigate carbon increases in the atmosphere that, as in Germany and other countries, they have violated international law with illegal experiments.

Another study has found that fertilizing the oceans with iron to produce more carbon-eating algae will not work as those ecological activists have envisioned. 


Whether dubbed “climate extremes” or “global weirding”, we have been witnessing some surprising and concerning weather events. In Europe, seasons seem to be changing, but not consistently. Since the turn of the millennium, the UK in particular has experienced record-breaking summer heatwaves, extraordinary rainfall in different seasons, and winters extreme in both warmth and cold. Something seems wrong, and we don’t have a complete understanding of what is going on.

Though hyper-exaggerated pictures of garbage patches and models extrapolated from a fishing line study in the 1980s get all of the media attention when it comes to pollution, it causes activist groups to raise money by focusing on the wrong thing. The most efficient way to clean up ocean plastics and avoid harming ecosystems is to stop litter on the coasts.