Earthweek: a diary of the planet

For the week ending Friday, Sept. 23. By Steve Newman

Earlier melt

Winter ice on more than

117 million lakes at higher latitudes is melting about eight days earlier because of global heating. Iestyn Woolway of Bangor University in Wales says the earlier melt is affecting plants and wildlife while altering the local climate. Ice currently forms on more than half of the world's lakes, with 90% of them located north of 30 degrees in latitude. Woolway says lakes will eventually be free of ice 15 to 45 days earlier.

Rise and sink

A study finds that parts of many coastal cities are sinking more quickly than the rise in sea level. The finding means that those communities are doubly threatened, and not just from the rising tides caused by glacial melt and the thermal expansion of the waters. An international team found that all of the world's largest seaside cities studied had some amount of land subsidence, with some areas sinking faster than the seas were rising. Land subsidence is caused by the extraction of groundwater and natural gas, and by the weight of buildings and other structures.

Ant kingdoms

German and Chinese researchers say they know the approximate number of ants crawling across the planet. Based on data from 489 ant studies, they determined there are 20 quadrillion individual ants, with a dry weight far heavier than that of all the wild birds and mammals on the planet combined. The number 20 quadrillion is 20 followed by 15 zeros. For every human, there are nearly 2.5 million ants scurrying, eating and breeding across the landscape. “They are very important for nutrient cycling, decomposition processes, plant seed dispersal and the perturbation of soil,” said entomologist Patrick Schultheiss of Germany's University of Würzburg. Taupo rumblings New Zealand volcanologists are concerned by swarms of tremors beneath the caldera lake that was the site of Earth's largest eruption of the past 5,000 years. That eruption of Taupo devastated a large area of the North Island.

Arctic blooms

Blooms of algae that were observed in the Arctic Ocean in 2014 may have been amplified by smoke from wildfires that year. “For a bloom that large to occur, the area would need a substantial influx of new nitrogen supply, as the Arctic Ocean is nitrogen-depleted,” says Douglas Hamilton of North Carolina State University. He and colleagues determined the nitrogen probably came from smoke emitted by the Siberian blazes. Peat in the thawing permafrost is rich in nitrogen, which he says stimulated the algae blooms.