Scientists have observed unexpected changes in the seawater salinity and they are increasingly concerned about the potential impact on ocean currents. The salinity of seawater can accelerate the water cycle which can cause extreme weather events like floods and drought.
To investigate the issue of ocean salinity scientists have boarded the research vessel Knorr, which set sail on September 6, 2012. NASA's Aquarius instrument is part of a separate research project that has been measuring seawater salinity from space since August 2011.
In addition to ocean salinity, researchers are exploring the water cycle which involves the ways that water circulates between the Earth's oceans, atmosphere, and land. This process involves precipitation and return to the atmosphere by evaporation and transpiration.
Although seawater is not uniformly saline throughout the world, the vast majority of seawater has a salinity level between 3.1 percent and 3.8 percent. Ocean salinity has been stable for billions of years, however scientists have observed that the salinity of seawater has been changing over the course of the last five decades.
These changes in salinity are accelerating the water cycle. As global temperatures get warmer, evaporation increases, altering the frequency, strength and distribution of rainfall around the planet.
Salinity, water cycle, temperature and weather are interconnected phenomenon. Ocean salinity is important because it affects ocean circulation; this in turn affects ocean temperatures, which can alter the weather.
Seawater which is high in saline can cause radical alterations in weather patterns. Salty water has a tendency to sink while warmer water rises to the surface, this impacts ocean currents which then impact the weather.
Research published in the journal Nature in 2006, indicated that sudden decreases in temperature over Greenland and tropical rainfall patterns during the last Ice Age are linked to rapid changes in the salinity of the North Atlantic Ocean.
Decades of research has demonstrated that the salty parts of the oceans have become saltier and the fresh regions have become fresher. Many scientists claim they do not know why this is happening, but on Wednesday September 5, 2012, Ray Schmitt, a senior scientist at the Woods Hole Oceanographic Institution, told journalists that he believes global warming may be driving these changes.
"Climate is changing all the time, and some of that change is due to natural variation," Schmitt said. "The 50-year trend we are talking about, most of us believe is really due to the general trend of global warming."
A warming planet can accelerate the water cycle making dry regions drier and high rainfall regions wetter. Although factors like wind can affect ocean salinity, the primary factor appears to be evaporation caused by warming. According to NASA's Salinity Processes in the Upper Ocean Regional Study (SPURS), we see 86 percent of global evaporation and 78 percent of global precipitation over the world's oceans. The oceans have more evaporation as compared to precipitation, which makes the water saltier, whereas in areas where there is more precipitation, the water is fresher.
According to 2009 research out of the UK, big shifts in salinity may indicate severe droughts and floods, perhaps even accelerated global warming. This research suggested that the amount of salt in seawater is varying in direct response to anthropogenic climate change. The UK study further indicated that global warming is changing precipitation patterns causing increased evaporation in subtropical zones; more precipitation towards the poles and higher concentrations of salt in the North Atlantic.
Evidence that the world's water cycle has intensified is contained in 2010 research published in the American Journal of Climate. According to this study, co-authored by CSIRO scientists Paul Durack and Dr Susan Wijffels, the surface warming we have seen over the past 50 years has penetrated deep into the ocean.
"This is further confirmation from the global ocean that the Earth's water cycle has accelerated," says Mr Durack.
The salinity of the oceans is also connected to CO2. Changes in the salinity of the oceans contribute to global changes in carbon dioxide as waters with more saline are less soluble to carbon dioxide.
We are all intimately connected to the ocean; it is the ultimate source of much of the water we drink and much of the air we breathe. The ocean directly feeds millions of people and absorbs a great deal of the air and water pollution. Our oceans are under threat but no single threat is more daunting than the acceleration of the water cycle caused by increased seawater salinity.
Richard Matthews is a consultant, eco-entrepreneur, green investor and author of numerous articles on sustainable positioning, eco-economics and enviro-politics. He is the owner of The Green Market Oracle, a leading sustainable business blog and one of the Web’s most comprehensive resources on the business of the environment. Find The Green Market on Facebook and follow The Green Market’s twitter feed.
Image credit: NASA Earth Observatory