Salty dogs

From morning till night some weathered salty sea men fish to classic rock.

World's wind and waves have been rising for decades



Challenges in the use of Satellite Wind and Wave Products in Marine Forecasting (Stanley Wilson) from IODE OceanTeacher

From NewScientist

Wind speeds and wave heights over the world's oceans have been rising for the past quarter-century.
It's unclear if this is a short-term trend, or a symptom of longer-term climatic change.
Either way, more frequent hurricanes and cyclones could be on the horizon.

Ian Young at the Australian National University in Canberra and colleagues analysed satellite data from 1985 to 2008 to calculate wave heights and wind speeds over the world's oceans.
They found that winds had strengthened – speeding up over most of the world's oceans by 0.25 to 0.5 per cent, on average, each year.
Overall, wind speeds were 5 to 10 per cent faster than they had been 20 years earlier.

The trend was most pronounced for the strongest winds.
For instance, the very fastest 1 per cent of winds were getting stronger by 0.75 per cent per year, says Young.

Average wave height was also on the rise, but less so; and the highest waves showed the strongest trend.

The results were compared against conventional measurements taken from deep-water buoys and numerical modelling.
"There is variability, but the same general features are observed," Young says.

From space to sea

Previous attempts to investigate these phenomena used observations from ships and buoys, but these could generally provide only a regional picture.
Using altimeter data from satellites allowed the team to detect decadal trends on a global scale for the first time.

Satellite altimeters use radar to measure the height of points on the Earth's surface, and can measure wave height very precisely.
Measuring the amount of backscattering from the radar signals, meanwhile, can help calculate wind speed.

The global view afforded by the satellites reveals stronger trends in some areas than in others.
For example, both wave height and wind speed have been increasing more rapidly in the oceans of the southern hemisphere than in the north.

Wave driver

Young can only speculate on what is causing the increases.
"If we have oceans that are warming, that energy could feed storms, which increase wind speeds and wave heights," he says.
But with a data series that covers just two decades, it's too early to tell whether there's a long-term trend at work. "We don't know the driving force."

Considering there are so many regional forces influencing waves and wind, "it's surprising that there is such a uniform trend", says Mark Hemer, a wave researcher at the Centre for Australian Weather and Climate Research in Hobart, Tasmania.
Variability in winds and waves associated with weather systems such as El Niño and La Niña, the North Atlantic Oscillation and the Southern Annular Mode could all help to explain it, he says.

In either case, if winds continue to strengthen and waves to rise – even if only for a few years – it suggests more intense storms, hurricanes and cyclones are on the horizon, says Young.

However, Tom Baldock, a coastal engineer at the University of Queensland in St Lucia, Australia, says that although there is no reason to doubt the analysis, it doesn't mean more coastal natural disasters will necessarily ensue.
"Tornados, hurricanes and cyclones occur through complicated regional weather conditions, and are not just related to wind speed and wave height," he says.
For example, there are higher wind speeds at high latitudes, but most cyclones hit around the equator.

The new study may be more relevant to the burgeoning offshore gas, wind, wave and tidal power industries, Baldock thinks.
"Larger waves are a hazard for any offshore construction."

Links :

• ScienceMag : Global trends in wind speed and wave height
• ScienceNews : Global gale warning
  

Big spring tide extremes in time-lapse

Grande Marée (coefficient 118) from Benoit Stichelbaut
Coincidence of perigean and spring tidal conditions

resulting in the highest high and the lowest low tides

 Anse du Minaouët (Concarneau) with the Marine GeoGarage

-> localization in the Marine GeoGarage

Links :

• Marine GeoGarage blog : Super full moon
  
• Wikipedia

Image of the week : Cat Island, Bahamas

-> Localization in the Marine GeoGarage

From NASA

Cat Island is one of 29 islands, 661 cays, and 2,387 islets that form the Commonwealth of the Bahamas.
Named San Salvador prior to 1925, Cat Island has been put forward as a candidate for where Christopher Columbus may have made his first landfall in the Americas.

Mount Alvernia—the highest point in the Bahamas, with an elevation of approximately 63 meters (206 feet) above sea level—is located on the southeastern part of the island.
Like most other islands in the Bahamas, Cat Island is located on a large depositional platform that is composed mainly of carbonate sediments and surrounding reefs.
The approximately 77 kilometer-long island (48 miles) is the part of the platform continuously exposed above water, which allows for soil development (brown to tan areas) and the growth of vegetation.

Shallow water to the west-southwest (below the island in this view) appears bright blue, in contrast to the deeper ocean waters to the north, east, and south.
In this astronaut photograph, the ocean surface near the southeastern half of the island has a slight grey tinge due to sunglint, or light reflecting off the water surface back towards the International Space Station.
Small white cumulus clouds obscure some parts of the island.

Cat Island is inhabited, and had a total population of 1,647 in 2000, according to the Department of Statistics of the Bahamas.
The smaller island of Little San Salvador to the west is privately owned and used as a port of call for cruise ships.

Cat Island may have derived its name from Arthur Catt, the famous British sea captain or notorious pirate.
A competing source for the name are the hordes of wild cats that the English encountered here on arrival in the 1600s.
The cats were said to be descendants of their tamer cousins orphaned by the early Spanish colonists in their rush to find the gold of South America.

This boot-shaped, untamed island is one of the most beautiful and fertile of The Bahamas.
A lush sanctuary, it provides tranquility for those seeking an escape from the pressures of modern civilization.
Others thought so too, like Father Jerome, a penitent hermit who built a medieval monastery hewn from the limestone cliffs atop 206-foot Mt. Alvernia, a place for meditation.
From these high cliffs, there is a marvelous view down to densely-forested foothills and 60 miles of deserted pink-and-white-sand beach.

Cat Island was once home to one of the more prosperous Loyalist colonies of the Out Islands.
The island gained its wealth from the numerous cotton plantations established during the 1700s.
Now, vine-covered, semi-ruined mansions and stone walls from farms where cattle were penned and pineapples grown, play hide and seek within the tropical flowers, grass and sand.
Crumbling remnants of slave villages and artifacts in Arawak caves whisper of a life long past.
Descendants of those early settlers remain in the same towns of their ancestors.

Links :

• The Islands of the Bahamas : Cat Island

Brian Skerry reveals ocean's glory -- and horror

From TED

Photographer Brian Skerry shoots life above and below the waves -- as he puts it, both the horror and the magic of the ocean.
Sharing amazing, intimate shots of undersea creatures, he shows how powerful images can help make change.

Using the camera as his tool of communication, Brian Skerry has spent the past three decades telling the stories of the ocean.
His images portray not only the aesthetic wonder of the ocean but display an intense journalistic drive for relevance.
Skerry’s work brings to light the many pressing issues facing our oceans and its inhabitants. Typically spending eight months of the year in the field, he often face extreme conditions to capture his subjects.
He has lived on the bottom of the sea, spent months aboard fishing boats and dived beneath the Arctic ice to get his shot.
He has spent over 10,000 hours underwater.

Links :

• NationalGeographic : Brian Skerry
• Photography : Brian Skerry, geographic photographer profiled
  
• YouTube : Brian Skerry describes the exhiliration of an up-close encounter with a curious, 45-foot-long right whale