Melting of Antarctic Ice Sheets Is Making Southern Ocean Less Salty
Melting Antarctic ice sheets are measurably reducing the salinity of the Southern Ocean. The research, published Thursday in Nature, notes that more freshwater entering the ocean "is more important for changes in global climate than has been appreciated so far."
Scientists have seen a reduction in salinity of the waters around Antarctica over the past decades. They haven't understood why until now. The study—by researchers from ETH Zurich, the GEOMAR Helmholtz Centre for Ocean Research Kiel and the University of Hamburg—describes a process whereby sea ice forms each winter, releasing salt in the seawater, then drifts northward and melts in the summer, spreading fresh water over a wide area.
On average, seawater is about 3.5 percent salts, mainly sodium chloride. Salt water is denser than fresh water, and the freezing point of water goes down as the amount of dissolved salts goes up. If all the salt in the world's oceans were removed and spread over the Earth, it would cover the planet in a 500-foot thick salt lick.
But salinity is not uniform across the world's waters. The highest salt content is generally found in the center of ocean basins, away from continents and the fresh water flowing from their rivers every day. Equatorial waters, where evaporation is highest, also boast above-average salinity. But these are not constant throughout the year.
Ocean circulation is driven by surface winds, temperature and salinity. Cooler, high-salinity water sinks to great depths, while lower-salinity water, which is less dense, rises. Over a long period—about 1,000 years—the Global Conveyor Belt moves water around the oceans in response to temperate and salinity.
The maximum seasonal ice cover in the Southern Ocean now reaches further north than it did 30 years ago. The German and Swiss study explains, "This expansion is mainly due to a stronger transport of sea ice that has pushed the sea-ice edge further to the north." The northernmost edge of the ice at maximum is at about 60 degrees south.
That may seem paradoxical in the face of a warming planet, but NASA explains: "Just as the temperatures in some regions of the planet are colder than average, even in our warming world, Antarctic sea ice has been increasing and bucking the overall trend of ice loss."
The significance of the greater mass of Antarctic sea ice is that, as it melts each summer, the fresh water sinks to a depth of about 600 to 1,500 meters, a region known as the Antarctic Intermediate Water. It then spreads north to the equator, into the eastern Atlantic and as far as the Iberian Peninsula.
As the water in the upper layers of the ocean become fresher and less dense, they may block the heavier, saltier waters below from rising to the surface. This is a process known as stratification.
James Hansen, the former NASA scientist, pointed to stratification as a potential wild card in the climate disruption process. He thinks that it could accelerate the melting of the Greenland and Antarctic glaciers, and perhaps change current patterns in the Atlantic. Research published Aug. 23 in Nature found evidence that stratification is occurring in Prydz Bay in East Antarctica.
In announcing the German and Swiss study, the researchers noted, "So far, the Southern Ocean has acted as a climate regulator and carbon sink: climate models show that this ocean has absorbed around three quarters of the excess heat. The Southern Ocean has also taken up around half the total amount of anthropogenic carbon dioxide absorbed by the world's oceans."
Further studies will test these theories, and new satellites will help researchers better observe the ocean and sea ice. The Southern Ocean will get more attention in the years to come.
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If weather is your mood, climate is your personality. That's an analogy some scientists use to help explain the difference between two words people often get mixed up.
Size Matters<p>Climates are a bit like woven tapestries. The big picture is important, no question. But so are all the seemingly minor details found inside the larger whole.</p><p><a href="https://research-information.bris.ac.uk/en/persons/tommaso-jucker" target="_blank">Tommaso Jucker</a> is an environmental scientist at the University of Bristol. In an email, Jucker says he'd define the term microclimate as "the suite of climatic conditions (temperature, rainfall, humidity, solar radiation) measured in localized areas, typically near the ground and at spatial scales that are directly relevant to ecological processes."</p><p>We'll talk about that last bit in a minute. But first, there's another criteria to discuss. According to some researchers, a microclimate — by definition — must differ from the larger area that surrounds it.</p><p><a href="https://www.cfc.umt.edu/research/paleoecologylab/publications/Davis_et_al_2019_Ecography.pdf" target="_blank">Forests</a> provide us with some great examples. "The climate near the ground in a tropical rainforest is dramatically different from the climate in the canopy 50 meters [164 feet] above," says University of Montana ecologist <a href="https://www.cfc.umt.edu/personnel/details.php?ID=1110" target="_blank">Solomon Dobrowski</a> in an email. "This vertical gradient among other factors allows for the staggering biodiversity we see in the tropics."</p><p>Likewise, scientists observed that a 2015 partial <a href="https://animals.howstuffworks.com/insects/bees-stopped-buzzing-during-2017-solar-eclipse.htm" target="_blank">solar eclipse</a> caused the air temperature of an Eastern European meadow to <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/wea.2802" target="_blank">change more dramatically</a> than it did in a nearby forest. That's because trees provide not only shade, but their leaves also reflect solar radiation. At the same time, forests tend to reduce wind speeds.</p><p>All those factors add up. A 2019 review of 98 wooded places — spread out across five continents — found that forests are 7.2 degrees Fahrenheit (4 degrees Celsius) <a href="https://natureecoevocommunity.nature.com/posts/47363-forests-protect-animals-and-plants-against-warming" target="_blank">cooler on average</a> than the areas outside them.</p><p>Now if you hate the cold, don't worry; there's a cozy exception to the rule. According to that same study, forests are usually 1.8 degrees Fahrenheit (1 degree Celsius) warmer than the external environment during the wintertime. Pretty cool.</p>
A Bug's Life<p>When does a microclimate stop being, well, micro? In other words, is there a maximum size we should be aware of when discussing them?</p><p>Depends on who you ask. "In terms of horizontal scale, some have defined 'microclimate' as anything that is less than 100 meters [328 feet] in range," Jucker says. "I'm personally less prescriptive about this."</p><p>Instead, he says the "scale at which we want to measure [a particular] microclimate" ought to be "dictated" by the questions we're trying to answer.</p><p>"If I want to know how temperature affects the photosynthesis of a leaf, I should be measuring temperature at centimeter scale," Jucker explains. "If I want to know if and how temperature affects the habitat preference of a large, mobile mammal, it's probably more relevant to capture temperature variation across [tens to hundreds] of meters."</p><p>For instance, solitary plants have the power to generate itty-bitty microclimates. Just ask <a href="https://www.colorado.edu/geography/peter-blanken-0" target="_blank">Peter Blanken</a>, a geography professor at the University of Colorado, Boulder and the co-author of the 2016 book, "<a href="https://amzn.to/2XN6FT8" target="_blank">Microclimate and Local Climate</a>."</p>
The urban heat island effect is a good example of how microclimates work. NOAA
Microclimates on a Grand Scale<p>It's no secret that our planet is going through some rough times at the macro level. The global temperature is <a href="https://climate.nasa.gov/vital-signs/global-temperature/" target="_blank">climbing</a>; nine out of the <a href="https://www.noaa.gov/news/2019-was-2nd-hottest-year-on-record-for-earth-say-noaa-nasa" target="_blank">10 hottest years on record</a> have occurred since 2005. And by one recent estimate, roughly 1 million species around the world are <a href="https://ipbes.net/sites/default/files/2020-02/ipbes_global_assessment_report_summary_for_policymakers_en.pdf" target="_blank">facing extinction</a> due to human activities.</p><p>"One of the big questions that ecologists and environmental scientists are trying to answer right now is how will individual species and whole ecosystems respond to rapid climate change and habitat loss," says Jucker. "...To me, [microclimates are] a key component of this research — if we don't measure and understand climate at the appropriate scale, then predicting how things will change in the future becomes a lot harder."</p><p>Developers have long understood the impact small-scale climates have on our daily lives. <a href="https://science.howstuffworks.com/environmental/green-science/urban-heat-island.htm#pt0" target="_blank">Urban heat islands</a> are cities that have higher temperatures than neighboring rural areas.</p><p>Plants release vapors that can moderate local climates. But in cities, natural greenery is often scarce. To make matters worse, plenty of our roads and buildings have a bad habit of absorbing or re-emitting heat from the sun. <a href="https://www.google.com/books/edition/Microclimate_and_Local_Climate/LHUZDAAAQBAJ?hl=en&gbpv=1&bsq=urban%20heat%20island" target="_blank">Vehicle emissions</a> don't exactly help the situation.</p><p>Still, it's not like Boston or Beijing are thermal monoliths. Sometimes, the documented temperatures <a href="https://e360.yale.edu/features/can-we-turn-down-the-temperature-on-urban-heat-islands" target="_blank">within a single city</a> vary by 15 to 20 degrees Fahrenheit (8.3 to 11.1 degrees Celsius).</p><p>That's where metro parks and city trees come in. They have nice cooling effects on nearby neighborhoods. "Several cities around the world have developed programs to increase urban green spaces," says Blanken. "Tree planting programs and green roof programs, have been shown to lower surface temperatures, decrease air pollution and decrease surface water runoff (urban flash-flooding) in urban areas."</p>
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By Jeff Berardelli
Note: This story was originally published on August 6, 2020
If asked to recall a hurricane, odds are you'd immediately invoke memorable names like Sandy, Katrina or Harvey. You'd probably even remember something specific about the impact of the storm. But if asked to recall a heat wave, a vague recollection that it was hot during your last summer vacation may be about as specific as you can get.
<div id="ecf36" class="rm-shortcode" data-rm-shortcode-id="c2dcc9d48a6cd61f247df1544539a783"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1290959314132361216" data-partner="rebelmouse"><div style="margin:1em 0">Naming heatwaves is a good idea—making the abstract concrete, the invisible visible. Why should hurricanes and wild… https://t.co/hDWgYb79Ob</div> — Ed Maibach (@Ed Maibach)<a href="https://twitter.com/MaibachEd/statuses/1290959314132361216">1596623660.0</a></blockquote></div>
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One of the challenges of renewable power is how to store clean energy from the sun, wind and geothermal sources. Now, a new study and advances in nanotechnology have found a method that may relieve the burden on supercapacitor storage. This method turns bricks into batteries, meaning that buildings themselves may one day be used to store and generate power, Science Times reported.
Bricks are a preferred building tool for their durability and resilience against heat and frost since they do not shrink, expand or warp in a way that compromises infrastructure. They are also reusable. What was unknown, until now, is that they can be altered to store electrical energy, according to a new study published in Nature Communications.
The scientists behind the study figured out a way to modify bricks in order to use their iconic red hue, which comes from hematite, an iron oxide, to store enough electricity to power devices, Gizmodo reported. To do that, the researchers filled bricks' pores with a nanofiber made from a conducting plastic that can store an electrical charge.
The first bricks they modified stored enough of a charge to power a small light. They can be charged in just 13 minutes and hold 10,000 charges, but the challenge is getting them to hold a much larger charge, making the technology a distant proposition.
If the capacity can be increased, researchers believe bricks can be used as a cheap alternative to lithium ion batteries — the same batteries used in laptops, phones and tablets.
The first power bricks are only one percent of a lithium-ion battery, but storage capacity can be increased tenfold by adding materials like metal oxides, Julio D'Arcy, a researcher at Washington University in St. Louis, Missouri, who contributed to the paper and was part of the research team, told The Guardian. But only when the storage capacity is scaled up would bricks become commercially viable.
"A solar cell on the roof of your house has to store electricity somewhere and typically we use batteries," D'Arcy told The Guardian. "What we have done is provide a new 'food-for-thought' option, but we're not there yet.
"If [that can happen], this technology is way cheaper than lithium ion batteries," D'Arcy added. "It would be a different world and you would not hear the words 'lithium ion battery' again."
One of the concerns about a warming planet is the feedback loop that will emerge. That is, as the planet warms, it will melt permafrost, which will release trapped carbon and lead to more warming and more melting. Now, a new study has shown that the feedback loop won't only happen in the nether regions of the north and south, but in the tropics as well, according to a new paper in Nature.
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