Climate Change

Rising Seas
http://ngm.nationalgeographic.com/2013/09/rising-seas/folger-text

As the planet warms, the sea rises. Coastlines flood. What will we protect? What will we abandon? How will we face the danger of rising seas?
 
http://www.nytimes.com/2013/08/25/u...ng-dry-in-florida.html?hp&_r=0&pagewanted=all

FORT LAUDERDALE, Fla. — With inviting beaches that run for miles along South Florida’s shores, it is easy to put sand into the same category as turbo air-conditioning and a decent mojito — something ever present and easily taken for granted.

As it turns out, though, sand is not forever. Constant erosion from storms and tides and a rising sea level continue to swallow up chunks of beach along Florida’s Atlantic coastline. Communities have spent the last few decades replenishing their beaches with dredged-up sand.

But in South Florida — Miami-Dade, Broward and Palm Beach Counties — concerns over erosion and the quest for sand are particularly urgent for one reason: there is almost no sand left offshore to replenish the beaches.

In these communities, sand is far from disposable; it is a precious commodity. So precious, in fact, that it has set off skirmishes among counties and has unleashed an intense hunt for more offshore sand by federal, state and local officials who are already fretting over the next big storm. No idea is too far-fetched in this quest, not even a proposal to grind down recycled glass and transform it into beach sand. The once-shelved idea is now being reconsidered by Broward County.

The situation is so dire that two counties to the north — St. Lucie and Martin — are being asked to donate their own offshore sand in the spirit of neighborliness.

“You have counties starting wars with each other over sand,” said Kristin Jacobs, the Broward County mayor, who has embraced the recycled glass idea as a possible stopgap. “Everybody feels like these other counties are going to steal their sand.”

St. Lucie and Martin Counties are none too keen to sacrifice their sand for the pleasures of South Florida. The last time the idea was mentioned, in 2006, it engendered accusations of subterfuge and raised so much ire that it was dropped.

If a recent spate of public meetings on the issue held by the Army Corps of Engineers is any measure, little has changed, despite a new study by the corps that says the two counties have enough offshore sand for at least 50 years.

“What happens in 50 years when all that sand is gone?” asked Frannie Hutchinson, a St. Lucie County commissioner. “Where are we supposed to go then? I told them to take their sand shovels and sand buckets and go home and come up with a better plan.”

In a state where the lure of pristine beaches is pivotal to a robust economy, hoarding sand is not unlike stocking the basement with toilet paper, water and peanut butter. One never knows when the next storm could sweep away a beach and wreak havoc on beach communities.

“When we got hit with back-to-back hurricanes, we had no beach in front of our infrastructures: A1A was wiped out,” Ms. Hutchinson said, referring to storms that engulfed a busy beachfront road.

The reason for all this agitation is straightforward: Miami-Dade County is officially out of offshore sand, which is environmentally sound and easily accessible. The last piles will be depleted in February, when sand replenishment is completed on the beach of the affluent village of Bal Harbour.

Broward County is not much better off; its offshore sand is nearly depleted. And Palm Beach County’s stocks are dwindling rapidly.
 
The Greenland and Antarctic ice sheets both possess hydrological systems that allow water accumulating from the melting of surface ice to be transported to the base of the ice sheet.

If that water, when it reaches the ice-bedrock interface, is distributed over large areas, it will lubricate rapid ice sheet flow toward the sea. Bamber et al. report the existence of a large, 750-km-long subglacial canyon in northern Greenland, which may act as a channel for the transport of basal meltwater to the margin of the ice sheet and thus influence overall ice sheet dynamics.


Bamber JL, Siegert MJ, Griggs JA, Marshall SJ, Spada G. Paleofluvial Mega-Canyon Beneath the Central Greenland Ice Sheet. Science 2013;341(6149):997-9. Paleofluvial Mega-Canyon Beneath the Central Greenland Ice Sheet

Subglacial topography plays an important role in modulating the distribution and flow of basal water. Where topography predates ice sheet inception, it can also reveal insights into former tectonic and geomorphological processes. Although such associations are known in Antarctica, little consideration has been given to them in Greenland, partly because much of the ice sheet bed is thought to be relatively flat and smooth. Here, we present evidence from ice-penetrating radar data for a 750-km-long subglacial canyon in northern Greenland that is likely to have influenced basal water flow from the ice sheet interior to the margin. We suggest that the mega-canyon predates ice sheet inception and will have influenced basal hydrology in Greenland over past glacial cycles.


Massive ‘Grand Canyon’ Found Hidden Beneath Greenland’s Ice - Hidden for all of human history, a 460 mile long canyon has been discovered below Greenland's ice sheet. Using radar data from NASA's Operation IceBridge and other airborne campaigns, scientists led by a team from the University of Bristol found the canyon runs from near the center of the island northward to the fjord of the Petermann Glacier.

[ame]https://www.youtube.com/watch?v=ENg9Hci9y3M[/ame]
 
Tropical ocean key to global warming ‘hiatus’
Surface cooling in equatorial Pacific drives decade-long pause in global temperature rise.
Tropical ocean key to global warming ‘hiatus’ : Nature News & Comment

A new study adds to mounting evidence that cooling in the tropical Pacific Ocean is the cause of the global warming hiatus, a slow-down in the rise of average temperatures that began around 1998.

The eastern equatorial Pacific is well known to have an outsize influence on global weather. Years-long ocean trends such as El Niño and La Niña cause alternate warming and cooling of the sea surface there, with effects on monsoons and temperatures around the world. Now a modelling study by researchers at the Scripps Institution of Oceanography in La Jolla, California, indicates that a decadal La Niña-like cooling trend affecting as little as 8% of Earth’s surface can explain the slower rise in global temperatures.


Kosaka Y, Xie S-P. Recent global-warming hiatus tied to equatorial Pacific surface cooling. Nature;advance online publication. http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12534.html

Despite the continued increase in atmospheric greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century, challenging the prevailing view that anthropogenic forcing causes climate warming.

Various mechanisms have been proposed for this hiatus in global warming, but their relative importance has not been quantified, hampering observational estimates of climate sensitivity. Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations. We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model.

Although the surface temperature prescription is limited to only 8.2% of the global surface, our model reproduces the annual-mean global temperature remarkably well with correlation coefficient r = 0.97 for 1970–2012 (which includes the current hiatus and a period of accelerated global warming). Moreover, our simulation captures major seasonal and regional characteristics of the hiatus, including the intensified Walker circulation, the winter cooling in northwestern North America and the prolonged drought in the southern USA.

Our results show that the current hiatus is part of natural climate variability, tied specifically to a La-Niña-like decadal cooling. Although similar decadal hiatus events may occur in the future, the multi-decadal warming trend is very likely to continue with greenhouse gas increase.
 
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Global Warming Is Very Real
Scientists are fighting deniers with irrefutable proof the planet is headed for catastrophe
http://www.rollingstone.com/politics/news/global-warming-is-very-real-20130912?print=true

On September 27th, a group of international scientists associated with the Intergovernmental Panel on Climate Change will gather in an old brick brewery in Stockholm and proclaim with near certainty that human activity is altering the planet in profound ways.

The IPCC's Fifth Assessment Report offers slam-dunk evidence that burning fossil fuels is the cause of most of the temperature increases of recent decades, and warn that sea levels could rise by almost three feet by the end of the century if we don't change our ways.

The report will underscore that the basic facts about climate change are more established than ever, and that the consequences of escalating carbon pollution are likely to mean that, as The New York Times recently argued, "babies being born now could live to see the early stages of a global calamity."
 
Arctic ice continues to thin, and thin, European satellite reveals
The thickness of the Arctic’s ice was whittled to a new recorded low this winter, according to data from the European Space Agency’s CyroSat mission.
Arctic ice continues to thin, and thin, European satellite reveals - CSMonitor.com

The thickness of the Arctic’s ice was whittled to a new winter low, according to data from the European Space Agency’s CryoSat mission. The ice’s volume, less than 15,000 cubic km between March and April, is a new data point in the long chronicle of Arctic ice decline, a process that scientists expect could be catastrophic for the planet.

The news from the ESA comes days after scientists reported that the ice’s decline this summer was less dramatic than the shrinkage during last year’s summer minimum. Rather than marking the resurgence of the Arctic ice, as some British newspapers have erroneously reported, the smaller-than-expected decline in breadth is understood by scientists as a small blip in what is otherwise a long-term ebbing of the ice.

And just as the ice is becoming less extensive, it is also becoming thinner – a trend that scientists point to as the most indicative sign that climate change is taking a toll on the Arctic.
 
Stanton TP, Shaw WJ, Truffer M, et al. Channelized Ice Melting in the Ocean Boundary Layer Beneath Pine Island Glacier, Antarctica. Science 2013;341(6151):1236-9. Channelized Ice Melting in the Ocean Boundary Layer Beneath Pine Island Glacier, Antarctica

Ice shelves play a key role in the mass balance of the Antarctic ice sheets by buttressing their seaward-flowing outlet glaciers; however, they are exposed to the underlying ocean and may weaken if ocean thermal forcing increases. An expedition to the ice shelf of the remote Pine Island Glacier, a major outlet of the West Antarctic Ice Sheet that has rapidly thinned and accelerated in recent decades, has been completed. Observations from geophysical surveys and long-term oceanographic instruments deployed down bore holes into the ocean cavity reveal a buoyancy-driven boundary layer within a basal channel that melts the channel apex by 0.06 meter per day, with near-zero melt rates along the flanks of the channel. A complex pattern of such channels is visible throughout the Pine Island Glacier shelf.
 
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Depoorter MA, Bamber JL, Griggs JA, et al. Calving fluxes and basal melt rates of Antarctic ice shelves. Nature;advance online publication. http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12567.html

Iceberg calving has been assumed to be the dominant cause of mass loss for the Antarctic ice sheet, with previous estimates of the calving flux exceeding 2,000?gigatonnes per year1, 2. More recently, the importance of melting by the ocean has been demonstrated close to the grounding line and near the calving front3, 4, 5. So far, however, no study has reliably quantified the calving flux and the basal mass balance (the balance between accretion and ablation at the ice-shelf base) for the whole of Antarctica. The distribution of fresh water in the Southern Ocean and its partitioning between the liquid and solid phases is therefore poorly constrained. Here we estimate the mass balance components for all ice shelves in Antarctica, using satellite measurements of calving flux and grounding-line flux, modelled ice-shelf snow accumulation rates6 and a regional scaling that accounts for unsurveyed areas. We obtain a total calving flux of 1,321?±?144?gigatonnes per year and a total basal mass balance of ?1,454?±?174?gigatonnes per year. This means that about half of the ice-sheet surface mass gain is lost through oceanic erosion before reaching the ice front, and the calving flux is about 34 per cent less than previous estimates derived from iceberg tracking1, 2, 7. In addition, the fraction of mass loss due to basal processes varies from about 10 to 90 per cent between ice shelves. We find a significant positive correlation between basal mass loss and surface elevation change for ice shelves experiencing surface lowering8 and enhanced discharge9. We suggest that basal mass loss is a valuable metric for predicting future ice-shelf vulnerability to oceanic forcing.
 
The 5 stages of climate denial are on display ahead of the IPCC report
Climate contrarians appear to be running damage control in the media before the next IPCC report is published
The 5 stages of climate denial are on display ahead of the IPCC report | Dana Nuccitelli | Environment | theguardian.com

The fifth Intergovernmental Panel on Climate Change (IPCC) report is due out on September 27th, and is expected to reaffirm with growing confidence that humans are driving global warming and climate change. In anticipation of the widespread news coverage of this auspicious report, climate contrarians appear to be in damage control mode, trying to build up skeptical spin in media climate stories.
 
Arctic sea ice melting faster than expected, UN report finds
Arctic sea ice melting faster than expected, UN report finds - FT.com

The Arctic’s summer sea ice is set to nearly vanish in less than 40 years, according to the final draft of a sweeping UN climate change report that sharply revises past estimates of how fast the icy north is melting.

“A nearly ice-free Arctic Ocean in September before mid-century is likely,” says the draft seen by the Financial Times of the first large-scale study in six years by the Intergovernmental Panel on Climate Change.
 
Cooler Year Fails to Shift Long-Term Trend of Arctic Sea Ice Melting
This year's ice cover remains far below the average of the last several decades
Cooler Year Fails to Shift Long-Term Trend of Arctic Sea Ice Melting: Scientific American

This year's Arctic sea ice cover currently is the sixth-lowest on modern record, a ranking that raises ongoing concerns about the speed of ice melt and the effects of ice loss on global weather patterns, geopolitical fights, indigenous peoples and wildlife, scientists said yesterday.

In an analysis, the National Snow and Ice Data Center said the sea ice extent as of Sept. 16 was 2 million square miles, an amount just below revised estimates for 2009, the former sixth place finisher, said Julienen Stroeve, a scientist at the center. While this year's annual minimum has not yet been officially declared and may not be for a few days, the sixth-place ranking for 2013 is not expected to change, she said.
 
Smith LC, Stephenson SR. New Trans-Arctic shipping routes navigable by midcentury. Proceedings of the National Academy of Sciences 2013;110(13):E1191-E5. New Trans-Arctic shipping routes navigable by midcentury

Recent historic observed lows in Arctic sea ice extent, together with climate model projections of additional ice reductions in the future, have fueled speculations of potential new trans-Arctic shipping routes linking the Atlantic and Pacific Oceans. However, numerical studies of how projected geophysical changes in sea ice will realistically impact ship navigation are lacking. To address this deficiency, we analyze seven climate model projections of sea ice properties, assuming two different climate change scenarios [representative concentration pathways (RCPs) 4.5 and 8.5] and two vessel classes, to assess future changes in peak season (September) Arctic shipping potential. By midcentury, changing sea ice conditions enable expanded September navigability for common open-water ships crossing the Arctic along the Northern Sea Route over the Russian Federation, robust new routes for moderately ice-strengthened (Polar Class 6) ships over the North Pole, and new routes through the Northwest Passage for both vessel classes. Although numerous other nonclimatic factors also limit Arctic shipping potential, these findings have important economic, strategic, environmental, and governance implications for the region.
 
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