The Labrador Current……..Credit: Wikipedia
Along the Eastern seaboard of the United States and Canada, at the bottom of the ocean shelves live a deep-sea coral known as a gorgonian or sea fan. The often intricate fan shape of these corals is used to filter food from the prevailing sea current. In the cold waters of the North Atlantic the corals grow slowly. As they grow, they form rings of a horny substance called gorgonin. The rings can be used just like they are in trees to count the years of growth, up to 700 years in these corals.
In addition to dating the corals with the rings, an international team of scientists from Switzerland, Canada, and the United States have released a joint study, published in the journal Proceedings of the National Academy of Sciences (PNAS) [Nutrient regime shift in the western North Atlantic indicated by compound-specific 15N of deep-sea gorgonian corals] that uses a new technique to analyze the coral’s food supply from an amino acid nitrogen signature.
This new technique, based on the detection of an isotope of nitrogen (15N) in specific amino acids is more accurate than old techniques that took bulk measurement of the nitrogen isotope. Using this technique the scientists were able to distinguish when the corals were receiving their food supply from northern water (the Labrador Current), which has less nitrogen, or from warmer more nitrogen rich southern waters of the Gulf Stream. Combining this with the ring dating, it appears that around 1970 the dominant current shifted to the warmer waters of the south. This has profound impact on the weather of Eastern Canada, the U.S., and Western Europe.
Scientists have been aware of these changes in currents for some time. It’s called the North Atlantic Oscillation and it has shifted many times over the millennia. This recent change replaces a 2,000 year dominance of the cold Labrador Current. The warmer water temperatures penetrating far into the North Atlantic can cause major changes in weather patterns, in particular exaggeration of warmer and wetter winters for Western Europe, and hot very dry summers in parts of Russia.
Is this evidence for global warming? Perhaps. The dating, coinciding as it does with the 1970’s onset of climate change, suggests more than a random coincidence. The possibility of influence by global warming is noted in the paper. However, this study presents only specific evidence of current change. The ‘reality’ it can show is change in corals. It can also show that the change in the corals is affected by specific currents and that alternations in these currents can be dated. Why these currents alternated is not something addressed in the data.
With this new information (evidence) it’s likely papers will be written that explore the causes for change in the currents. What’s important about this paper is the exploration of a new technique and how it can be used to develop testable data about something that may (or may not) be indicative of climate change. This is how climate studies are built, piece by piece. It’s slow, rarely conclusive and these days prematurely controversial work; but in the end it’s the data stupid.