Oceanography

Reefs are made up of many coral species that live in a mutually beneficial symbiotic relationship with microscopically small algae hosted in their tissue. These symbiont algae produce sugars that contribute to the diet of the coral in return for shelter and nutrients that are vital for algal growth.  A symbiotic association is vulnerable to changes in environmental conditions, like seawater temperature. Heat-stress induced loss of the algal partners from the coral host can result in the often fatal process known as 'coral bleaching'.  A new species of algae has been discovered in…

Researchers have quantified how the Greenland Ice Sheet reacted to a warm period 8,000-5,000 years ago, when temperatures were 2-4 degrees C warmer than present and so could inform us what might happen if the same occurred now.  Dr. Nicolaj Krog Larsen, Aarhus University in Denmark and Professor Kurt Kjær, Natural History Museum of Denmark, ventured off to Greenland to investigate how fast the Greenland Ice Sheet reacted to past warming. Over six summers, they cored lakes in the ice-free land surrounding the ice sheet. The lakes act as a valuable archive as they store glacial meltwater…

Remote monitoring of large swathes of otherwise inaccessible ocean using satellites reveals an alarming picture: ocean acidity. The Earth's oceans take up about a quarter of global CO2 emissions, which can turn the seawater more acidic, making it more difficult for some marine life to live. Rising CO2 emissions, and the increasing acidity of seawater projected over the next century, has the potential to devastate some marine ecosystems, a food resource on which we rely, and so careful monitoring of changes in ocean acidity is crucial. Total ocean alkalinity as viewed from space. Credit:…

There've been some recent environmental claims about methane seepage, flaming tapwater, but what were not staged have been due to nature.  It's a tale almost as old as earth. But outside environmental circles, science was always thinking about methane as much as CO2, because it has a 23X greater warming impact than CO2. Fortunately it is short-lived so trace seepage of methane from natural gas is nowhere near as devastating as CO2 from other forms of energy creation. Natural gas is why emissions from energy in America are back at early 1990s levels and emissions from coal, the dirtiest…

Arctic sea ice extent plunged 2001 to 2007 but then rebounded between 2007 and 2013. Warming world or not, periods of no change - and rapid change - at the world's northern reaches are the new normal. And perhaps the old normal as well. Natural ups and downs of temperature, wind and other factors mean that even as sea ice slowly melts, random weather can mask or enhance the long-term trend. For example, even in a warming world, there's still a one-in-three chance that any seven-year period would see no sea ice loss, such as in 2007-2013, a new analysis shows. And the chaotic nature of weather…

GOCE gravity satellite. ESA We might like to think of the earth as fixed and unmoving but that is not the case. Things are always shifting, even if we may not have noticed in the past. But when sea level changes are a political issue, it is important to have accurate data - and that means understanding all of the factors involved. Researchers at the National Oceanography Centre (NOC) have discovered that a ‘slope’ on the ocean surface in the Strait of Gibraltar is lowering the sea level in Europe by 7 centimeters, a finding which will help to more accurately predict future sea levels because…

Looks healthy, but still lacks the big predatory fish... how would it rate on the Promonitor Index? AF Johnson, CC BY-NC-SA By Andrew Frederick Johnson, University of California, San Diego We know that fishing has significant impacts on our oceans and the animals that live in them. Effects can range from habitat modification caused by bottom trawls, stock declines from overfishing or subtler consequences such as shifts in the structure and functioning of marine food webs. Although such effects are ubiquitous and happen across many different marine systems, the difficulty of producing a…

As the Earth warms and glaciers all over the world begin to melt, the natural concern has been how all of that extra water will contribute to sea level rise. Less considered is what happens to all of the organic carbon found in those glaciers when they melt. A new paper estimates what could happen if major ice sheets break down. Glaciers and ice sheets contain about 70 percent of the Earth's freshwater and ongoing melting is a major contributor to sea level rise. But, glaciers also store organic carbon derived from both primary production on the glaciers and deposition of materials such…

Scientists propose a new, potentially more accurate way, to measure the rate of sea level rise. Shutterstock By Carling Hay, Harvard University When you ask yourself what the biggest unanswered scientific questions are, “how did sea levels change over the past 100 years?” is unlikely to appear at the top of your list. After all, haven’t we already figured that out? It turns out that obtaining a complete picture of how our oceans have been changing is not a simple task, yet is vital for making future projections. In a paper published in Nature this week, my research group developed a more…

After mass bleaching in 1998, more than half of coral reefs in the Seychelles have slowly recovered. Nick Graham By John Pandolfi, The University of Queensland Coral reefs are the poster child for the damage people are doing to the world’s oceans. Overfishing, pollution and declining water quality have all taken their toll on reefs around the world. Perhaps the most famous example is Australia’s Great Barrier Reef, where half of the coral cover has disappeared over the past 25 years. But increasingly, coral reefs face additional threats: global warming and ocean acidification, which cause…