Oceanography

Antarctic sea ice reached a new record high extent this year, covering more of the southern oceans than it has since scientists began a long-term satellite record to map sea ice extent in the late 1970s. The Antarctic sea ice extent exceeded 7.72 million square miles (20 million square kilometers) for the first time since 1979, according to the National Snow and Ice Data Center. The ice extent stayed above this benchmark extent for several days. The average maximum extent between 1981 and 2010 was 7.23 million square miles (18.72 million square kilometers).  The new Antarctic sea ice…

Worth it for cheap cotton? Credit:so11e/flckr, CC BY-NC-ND By Anson Mackay, University College London The Aral Sea has reached a new low, literally and figuratively; new satellite images from NASA show that, for the first time in its recorded history, the largest basin has completely dried up. However, the Aral Sea has an interesting history – and as recently as 600-700 years ago it was as small, if not smaller, than today. The Aral recovered from that setback to become the world’s fourth largest lake, but things might not be so easy this time round. Today, more people than ever rely on…

Ice sheets were never simple. There is no magic knob that could be turned to optimize melting rates and movement, outside environmental press releases. A new paper in Nature this week shows that not only is meltwater not as simple as sometimes contended, we don't even know what we don't know. Observations of moulins (vertical conduits connecting water on top of the glacier down to the bed of the ice sheet) and boreholes in Greenland show that subglacial channels ameliorate the speedup caused by water delivery to the base of the ice sheet in the short term. By mid summer, however, the…

Farm runoff and urban pollution in the Hawaiian islands is causing sea turtle tumors, according to a study in PeerJ. The paper by researchers at  Duke University, the University of Hawaii and the National Oceanic and Atmospheric Administration finds that nitrogen in the runoff ends up in algae that the turtles eat, promoting the formation of tumors on the animals' eyes, flippers and internal organs. Nitrogen is a common byproduct from overuse of fertilizer. The scientists conducted the study to better understand the causes behind the tumor-forming disease Fibropapillomatosis, the…

There is less saline in Nordic Seas but that can't be blamed on more Arctic waters due to global warming. Instead, it is that the Gulf Stream has provided less salt.  The Nordic Seas have freshened substantially since 1950. This has happened at the same time as there has been observed increased river runoff and net ice melting in the Arctic. The concurrence of a less saline ocean and Arctic freshwater input has given the climate research community reason for concern, but a new study finds that the source of fresher Nordic Seas since 1950 is rooted in the saline Atlantic, as opposed to…

It may already be too late to stop Antarctic ice sliding into the ocean. Credit: EPA By Eelco Rohling, University of Southampton Ice sheets respond slowly to changes in climate, because they are so massive that they themselves dominate the climate conditions over and around them. But once they start flowing faster towards the shore and melting into the ocean the process takes centuries to reverse. Ice sheets are nature’s freight trains: tough to start moving, even harder to stop. We know this process has been going back and forth throughout history – it’s why we’ve had ice ages and warm…

Ice ebbs and flows, that is no secret - but lost in claims that ice is as widespread as ever is the reality that it is now thinner, and the difference is so noticeable the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite can detect it. The strength of gravity at Earth’s surface varies subtly from place to place owing to factors such as the planet’s rotation and the position of mountains and ocean trenches. Changes in the mass of large ice sheets can also cause small local variations in gravity. Recently, the high-resolution measurements from GOCE over Antarctica…

Arctic sea ice coverage declined to its annual minimum on September 17th and the National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder find that this year's minimum extent is similar to last year's and below the 1981-2010 average of 2.40 million square miles.  Over the 2014 summer, Arctic sea ice melted back from its maximum extent reached in March to a coverage area of 1.94 million square miles, according to analysis from NASA and NSIDC scientists.  "Arctic sea ice coverage in 2014 is the sixth lowest recorded since 1978. The summer started off…

In a global warming scenario, large areas of sea ice melt in the summer and when sea ice freezes over in the winter it is thinner and more reduced. But warmer Arctic summers could lead to an acceleration of global warming, because reduced sea ice in the Arctic will remove less CO2 from the atmosphere, Danish scientists report. "If our results are representative, then sea ice plays a greater role than expected, and we should take this into account in future global CO2 budgets", says Dorte Haubjerg Søgaard, PhD Fellow, Nordic Center for Earth Evolution, University of Southern Denmark and the…

By Charles Q. Choi, Inside Science It's a myth that all sharks will drown if they stop moving. However, scientists discovered that as the oceans grow more acidic this century, sharks may swim for longer times than before. These new findings suggest that rising atmospheric carbon dioxide levels causing this ocean acidification could significantly disrupt the lives of these predators, which are already in sharp decline globally. Since the beginning of the Industrial Revolution, the burning of fossil fuels has sharply increased atmospheric carbon dioxide levels, with concentrations of the…