43-year-old mystery of Polynya in Antarctica unraveled

A study led by NYU Abu Dhabi (NYUAD) Research Scientist Diana Francis has unraveled the four decade long mystery surrounding the occurrence of a mid-sea Polynya -- a body of unfrozen ocean that appeared within a thick body of ice during Antarctica's winter almost two years ago.

The Maud-Rise Polynya was spotted in mid September 2017 in the center of an ice pack in Antarctica's Lazarev Sea, causing researchers to question how this phenomenon occurred during Antarctica's coldest, winter months when ice is at its thickest. Due to its difficult access location, NYUAD scientists used a combination of satellite observations and reanalysis data to discover that cyclones (as intense as category 11 in the Beaufort Scale) and the strong winds that they carry over the ice pack cause ice to shift in opposite directions, which leads to the opening of the Polynya.

At the time of the discovery, the Maud-Rise Polynya was approximately 9,500 square kilometers large (equivalent to the landmass of the state of Connecticut), and grew by over 740 percent to 800,000 square kilometers within a month. Eventually, the Polynya merged with the open ocean once the ice started to retreat at the beginning of the austral summer months. Prior to 2017, this phenomenon has only been known to have occurred in the 1970s when satellite observations started to become more commonly used, and has baffled scientists ever since.

"Once opened, the Polynya works like a window through the sea-ice, transferring huge amounts of energy during winter between the ocean and the atmosphere." said Francis. "Because of their large size, mid-sea Polynyas are capable of impacting the climate regionally and globally as they modify the oceanic circulation. It is important for us to identify the triggers for their occurrence to improve their representation in the models and their effects on climate.

"Given the link between Polynya and cyclones we demonstrated in this study, it is speculated that Polynya events may become more frequent under warmer climate because these areas will be more exposed to more intense cyclones. Previous studies have shown that under warmer climate, polar cyclone activity will intensify and extratropical cyclones track will move toward Antarctica which could decrease the sea-ice extent and make Polynya areas, closer to the cyclones formation zone," she added.

Story Source:

Materials provided by New York University. Note: Content may be edited for style and length.

from Oceanography News -- ScienceDaily http://bit.ly/2ID0GtV
via IFTTT

Antarctica: The final frontier for marine biological invasions?

A new study looking at the implications of increased shipping activity and the impact on Antarctic marine biodiversity is published this week in the journal Global Change Biology. The research is an important step in the quest to understand whether invasive species, introduced by shipping, will find the Antarctic marine environment more hospitable as Antarctica's climate changes.

Analysis of ship location records, scientific databases and reports by researchers from British Antarctic Survey (BAS) and the University of Cambridge reveal that ship traffic in Antarctic waters has increased up to 10-fold since 1960s. This could mean that there is a greater risk that animals and plants, such as mussels and seaweed, could be transported to Antarctica.

The marine ecosystem in the Southern Ocean became largely isolated when the circumpolar current formed 15-30 million years ago. The region is considered to be biologically unique and conservation of Antarctic ecosystems is a global priority. Invasive species have the potential to alter the balance between species. In other parts of the world this has led to the collapse of fisheries and diminished ecosystem services.

This work provides the first holistic view of the risk of non-native species to the Antarctic marine environment. It informs future conservation management and policy.

Arlie McCarthy, lead author and marine ecologist at British Antarctic Survey and the Department of Zoology, University of Cambridge, says:

"We know that at present physical barriers, such as sea ice cover, ocean currents and water temperature, prevent non-native species establishing themselves in marine ecosystems around Antarctica. However, we need to understand the wider implications of changing environmental conditions and increased ship activity. Our study will help us determine the scale of the risk.

We know that some invasive species such as mussels, tunicates, bryozoans, and crabs that live on ship hulls have been observed in the Southern Ocean. There is no confirmed record of these becoming established as a population as yet but this is a threat for the future."

Very few studies of 'hull fouling' on Antarctic-going vessels have been carried out. Professor Lloyd Peck of British Antarctic Survey says:

"This work is an important early step towards protecting the unique biodiversity living on the seabed around Antarctica from human-introduced non-native species. Before effective measures can be taken, the risk must be quantified.

We need much more understanding of these issues and more effort to gauge the risks and develop the best conservation measures we can to at least try and minimise any future biodiversity losses in the Antarctic marine environment."

Dr David Aldridge, the Department of Zoology, University of Cambridge says:

"Invasive species are recognised as one of the biggest drivers of global biodiversity loss. While life in Antarctica may have once been relatively protected from the invasion of non-native marine species, our study reveals that human-mediated global change is increasing the likelihood of exposing life in the Southern Ocean to new and unprecedented challenges."

Story Source:

Materials provided by British Antarctic Survey. Note: Content may be edited for style and length.

from Oceanography News -- ScienceDaily http://bit.ly/2XEqVUj
via IFTTT

Carbon dioxide from Silicon Valley affects the chemistry of Monterey Bay

MBARI researchers recently measured high concentrations of carbon dioxide in air blowing out to sea from cities and agricultural areas, including Silicon Valley. In a new paper in PLOS ONE, they calculate that this previously undocumented process could increase the amount of carbon dioxide dissolving into coastal ocean waters by about 20 percent.

Extending their calculations to coastal areas around the world, the researchers estimate that this process could add 25 million additional tons of carbon dioxide to the ocean each year, which would account for roughly one percent of the ocean's total annual carbon dioxide uptake. This effect is not currently included in calculations of how much carbon dioxide is entering the ocean because of the burning of fossil fuels.

Less than half of the carbon dioxide that humans have released over the past 200 years has remained in the atmosphere. The remainder has been absorbed in almost equal proportions by the ocean and terrestrial ecosystems. How quickly carbon dioxide enters the ocean in any particular area depends on a number of factors, including the wind speed, the temperature of the water, and the relative concentrations of carbon dioxide in the surface waters and in the air just above the sea surface.

MBARI has been measuring carbon dioxide concentrations in the air and seawater of Monterey Bay almost continuously since 1993. But it wasn't until 2017 that researchers began looking carefully at the atmospheric data collected from sea-surface robots. "One of our summer interns, Diego Sancho-Gallegos, analyzed the atmospheric carbon dioxide data from our research moorings and found much higher levels than expected," explained MBARI Biological Oceanographer Francisco Chavez.

Chavez continued, "If these measurements had been taken on board a ship, researchers would have thought the extra carbon dioxide came from the ship's engine exhaust system and would have discounted them. But our moorings and surface robots do not release carbon dioxide to the atmosphere."

In early 2018 MBARI Research Assistant Devon Northcott started working on the data set, analyzing hourly carbon dioxide concentrations in the air over Monterey Bay. He noticed another striking pattern -- carbon dioxide concentrations peaked in the early morning.

Although atmospheric scientists had previously noticed early-morning peaks in carbon dioxide concentrations in some cities and agricultural areas, this was the first time such peaks had been measured over ocean waters. The finding also contradicted a common scientific assumption that concentrations of carbon dioxide over ocean areas do not vary much over time or space.

Northcott was able to track down the sources of this extra carbon dioxide using measurements made from a robotic surface vessel called a Wave Glider, which travels back and forth across Monterey Bay making measurements of carbon dioxide in the air and ocean for weeks at a time.

"Because we had measurements from the Wave Glider at many different locations around the bay," Northcott explained, "I could use the Wave Glider's position and the speed and direction of the wind to triangulate the direction the carbon dioxide was coming from."

The data suggested two main sources for the morning peaks in carbon dioxide -- the Salinas and Santa Clara Valleys. The Salinas Valley is one of California's largest agricultural areas, and many plants release carbon dioxide at night, which may explain why there was more carbon dioxide in the air from this region. Santa Clara Valley [aka Silicon Valley] is a dense urban area, where light winds and other atmospheric conditions in the early morning could concentrate carbon dioxide released from cars and factories.

Typical morning breezes blow directly from the Salinas Valley out across Monterey Bay. Morning breezes also carry air from the Santa Clara Valley southward and then west through a gap in the mountains (Hecker Pass) and out across Monterey Bay.

"We had this evidence that the carbon dioxide was coming from an urban area," explained Northcott. "But when we looked at the scientific literature, there was nothing about air from urban areas affecting the coastal ocean. People had thought about this, but no one had measured it systematically before."

The researchers see this paper not as a last word, but as a "wake-up call" to other scientists. "This brings up a lot of questions that we hope other researchers will look into," said Chavez. "One of first and most important things would be to make detailed measurements of carbon dioxide in the atmosphere and ocean in other coastal areas. We need to know if this is a global phenomenon. We would also like to get the atmospheric modelling community involved."

"We've estimated that this could increase the amount of carbon dioxide entering coastal waters by roughly 20 percent," said Chavez. "This could have an effect on the acidity of seawater in these areas. Unfortunately, we don't have any good way to measure this increase in acidity because carbon dioxide takes time to enter the ocean and carbon dioxide concentrations vary dramatically in coastal waters."

"There must be other pollutants in this urban air that are affecting the coastal ocean as well," he added.

"This is yet another case where the data from MBARI's autonomous robots and sensors has led us to new and unexpected discoveries," said Chavez. "Hopefully other scientists will see these results and will want to know if this is happening in their own backyards."

from Oceanography News -- ScienceDaily http://bit.ly/2XCOay2
via IFTTT

Soft tissue makes coral tougher in the face of climate change

Climate change and ocean warming threaten coral reefs and disrupt the harmonious relationship between corals and their symbiotic algae, a process known as "coral bleaching." However, a new study conducted by scientists at the University of Hawai'i (UH) at Mānoa and the California Academy of Sciences revealed soft tissues that cover the rocky coral skeleton promote the recovery of corals following a bleaching event.

These soft tissues, which are home to beneficial algae, represent a source of energy for corals. The study, led by Chris Wall, a graduate student at the Hawai'i Institute of Marine Biology (HIMB) in the UH Mānoa School of Ocean and Earth Science and Technology (SOEST), showed corals with thicker tissue may be better equipped to survive bleaching in a warming ocean.

Coral reefs are a vital resource to the people of Hawai'i and the state's economy in the form of tourism, diving, and recreational fisheries, in addition to protecting shorelines from storms and coastal erosion.

When corals are stressed, they lose the colorful algae living in their tissues, resulting in bleaching and sometimes death of the corals. These events have been historically rare in the Hawaiian Islands, but heat stress is becoming more widespread as a result of climate change. Repeated bleaching events in 2014 and 2015 show that Hawai'i is not immune to the effects of ocean warming.

"While we know a great deal about thermal stress and its effects on corals, we know comparatively little about how corals recover from bleaching in the real world, or how local factors, such as light or nutrients in seawater, can influence recovery from bleaching," said Wall.

In the fall of 2014, Wall and colleagues studied colonies of two species of corals, rice coral and finger coral, in Kāne'ohe Bay, O'ahu, Hawai'i, when seawater in the bay reached unusually high temperatures of 86F, which is near the maximum temperature Hawaiian corals can tolerate. The team was interested in how colonies that were sensitive to thermal stress responded to and recovered from bleaching compared to adjacent coral colonies that remained pigmented and did not bleach.

During the warming event and three months later, the team assessed the coral animals and their symbiotic algae, and throughout the study measured environmental factors including light levels, water temperatures, sedimentation rates, and seawater nutrients to better understand how environmental factors influenced the severity of coral bleaching and rates of recovery. The researchers also used naturally-occurring chemical signatures in coral tissues to test how corals were performing and what they were eating during and after stress.

"A coral's diet is based on food from their symbionts and the consumption of small organisms in seawater known as plankton, and these two sources supply the building blocks for coral tissues. But under bleaching, corals are left without their symbionts and are in effect starving. We wanted to know how corals overcome this nutritional dilemma -- were they relying on stored energy in their tissues (much like a bear in hibernation) or were they eating more plankton?"

The bleached colonies did not die and showed remarkable resilience, recovering from losses in both their symbionts and soft tissues within three months. This recovery was hastened by environmental factors, such as cooler water temperatures and water with low nutrient concentrations, which influenced coral tissues.

The researchers determined that coral tissues are very important in the bleaching recovery process and corals with abundant or thick tissues may be able to better survive and recover from bleaching stress. The stored energy in coral tissues, and not greater plankton feeding, served as food for corals during thermal stress and helped corals recover.

"Kāne'ohe Bay is a unique coral ecosystem that has rebounded from decades of human impacts. Therefore, corals in Kāne'ohe Bay may hold valuable lessons for science as we work to understand the basis for coral tolerance to the environmental challenges experienced today and those to come in the future as humans continue to change our global climate," said Wall.

In the future, the researchers will work to better understand what mechanisms underpin the coral animals' and their microbes' tolerance and vulnerability to ocean warming.

Story Source:

Materials provided by University of Hawaii at Manoa. Note: Content may be edited for style and length.

from Oceanography News -- ScienceDaily http://bit.ly/2Duvx7E
via IFTTT

Arctic warming will accelerate climate change and impact global economy

Carbon released into the atmosphere by the increasing loss of Arctic permafrost, combined with higher solar absorption by Earth's surface due to the melting of sea ice and land snow, will accelerate climate change -- and have a multi-trillion dollar impact on the world economy.

A new paper in Nature Communications reveals a combination of these factors has the potential to increase the long-term economic impact of climate change by just under $70 trillion, under mitigation levels consistent with current national pledges to cut carbon emissions (5% of the estimated total cost of climate change for this scenario).

Under the Intergovernmental Panel on Climate Change (IPCC) Paris Agreement target of global temperature rises being limited to 1.5C from pre-industrial levels, the extra impact drops to $25 trillion (4% of the total cost for this scenario). In both cases, the primary driver behind the additional costs is the emitted permafrost carbon.

The interdisciplinary research team hope their assessments will provide a better understanding of the socio-economic risks from climate change under different scenarios and help guide policy-makers towards prudent decisions on emissions reduction targets.

Researchers explored simulations of complex, state-of-the-art, physical models to quantify the strength of the permafrost carbon feedback (PCF), driven by the additional carbon released from thawing permafrost, and of the surface albedo feedback (SAF), driven by the extra solar energy absorbed by Earth's surface as the white sea ice and land snow cover declines, exposing darker ocean and land.

Nearly all climate policy studies to date have implied a constant SAF and zero PCF. However, recent observations and computer models show the permafrost feedback is the stronger of the two and that both are nonlinear, their strength changing in complex ways as the climate warms. This affects their impact on both the global climate and economy.

"Arctic sea ice and land snow currently contribute around a third each to the global albedo feedback," said lead author Dmitry Yumashev, of the Pentland Centre for Sustainability in Business at Lancaster University.

"These two components are set to peak for global temperatures within the range covered by the Paris Agreement, but if the climate warms further, the summer and spring sea ice and land snow covers will retreat further north and the albedo feedback will actually weaken.

"The permafrost feedback, however, grows progressively stronger in warmer climates. Both feedbacks are characterised by nonlinear responses to warming, including a varying lag between rising global temperature and permafrost carbon emissions.

"Compared with zero PCF and constant SAF from present-day climate -- legacy values used in climate policy modelling to this point -- the combined nonlinear PCF and SAF cause significant extra warming globally under low and medium emissions scenarios.

Low emissions scenarios in the study include meeting the 1.5°C and 2°C Paris Agreement targets relative to pre-industrial conditions by 2100, while medium emissions scenarios include mitigation levels consistent with current national pledges (NDCs). Under the NDCs, the world is set to warm by around 3°C relative to pre-industrial by 2100.

High emissions scenarios, such as the current business as usual trajectory (BaU) -- expected to lead to around 4°C of warming by 2100 and cause by far the highest impacts on ecosystems and societies -- are also included. Under these, the strength of the PCF reaches its peak and does not increase further, while the continued weakening of the SAF gradually cancels the warming effect of the PCF.

For the purposes of the research, other major planetary feedbacks, such as those driven by changes in clouds and water vapour in response to warming, are assumed to remain constant, supported by the last two generations of climate models.

Under all scenarios, using the nonlinear Arctic feedbacks compared to previous constant values leads to an increase to the total cost of climate change, consisting of the mitigation costs of cutting emissions, climate adaptation costs and residual climate-related impacts. The increases occur primarily through additional temperature-driven impacts on economy, ecosystems and human health, and additional impacts from sea level rise.

All costs were estimated using simulations in specially developed integrated assessment model PAGE-ICE, which includes simple statistical representations of the Arctic feedbacks derived from complex models. It has multiple updates to climate science and economics, including up-to-date uncertainty estimates.

Under the NDCs scenario, the additional estimated impact based on thousands of simulations of the nonlinear PCF and SAF is just under $70 trillion compared to their previously used values -- exceeding by around 10 times current estimates for long-terms economic gains from transit shipping routes and mineral resource extraction in the Arctic region.

With previous estimates for Arctic feedbacks, the total cost of climate change associated with the 1.5C and 2C scenarios is virtually the same and is around $600 trillion -- in comparison, the estimated cost of business as usual is around $2000 trillion. Nonlinear PCF and SAF add further $25 trillion to the $600 trillion figure for the 1.5C scenario and $34 trillion for the 2C scenario. Thus, the nonlinear Arctic feedbacks make the more ambitious 1.5C target marginally more economically attractive.

Dr Yumashev added: "Our findings support the need for more proactive mitigation measures to keep global temperature rise well below 2C.

"We hope our work will lead to further assessments of multiple nonlinear processes in the Earth's climate system, both those associated with the Arctic and beyond."

The authors of the study are Dmitry Yumashev, Gail Whiteman and Paul Young, of the Pentland Centre for Sustainability in Business and Lancaster Environment Centre at Lancaster University; Chris Hope, of the Judge Business School at the University of Cambridge; Kevin Schaefer, of the National Snow and Ice Date Center at the University of Colorado (USA); Kathrin Riemann-Campe, of the Alfred Wegener Institute (Germany); Fernando Iglesias-Suarez, of the Institute of Physical Chemistry Rocasolano (Spain); Elchin Jafarov, of the Los Alamos National Laboratory (USA); Eleanor J. Burke, of the UK Met Office; and Yasin Elshorbany, of the University of South Florida (USA).

from Oceanography News -- ScienceDaily http://bit.ly/2ISpQEn
via IFTTT

One million species risk extinction due to humans: Draft UN report - CNA

One million species risk extinction due to humans: Draft UN report  CNA

Up to one million species face extinction due to human influence, according to a draft UN report obtained by AFP that painstakingly catalogues how ...

from "mangroves" - Google News http://bit.ly/2Prr22H
via IFTTT

Will ocean seafood farming sink or swim? Study evaluates its potential - Phys.Org

Will ocean seafood farming sink or swim? Study evaluates its potential  Phys.Org

Seafood farming in the ocean—or marine aquaculture—is the fastest growing sector of the global food system, and it shows no sign of slowing. Open-ocean ...

from "mangroves" - Google News http://bit.ly/2UPHEao
via IFTTT