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Ocean Circulation in the North Atlantic: Why It Is Important for Scotland Nacli

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Ocean Circulation in the North Atlantic: Why It Is Important for Scotland Nacli TOPIC SHEET NUMBER 123 V1 OCEAN CIRCULATION IN THE NORTH ATLANTIC: WHY IT IS IMPORTANT FOR SCOTLAND NACLI The THOR Project What next? - NACLIM THOR stands for Thermo-Haline Overturning – The work of THOR will be continued until 2017 3 At Risk? and during 4 years (2008-2012), the in a new EU FP7 Collaborative Project: North project investigated the dynamics of the Atlantic Atlantic Climate (NACLIM). The main focus of the Ocean’s circulation and its impact on European project is to work towards more reliable seasonal climate. THOR’s scientists cut across all disciplines to decadal forecasts, but as knowledge of the of ocean science: from scientists observing the North Atlantic Circulation is key to achieving 2 ocean, to those creating reconstructions of the this, the observational efforts established under 1 past (based on marine fossil records) and those THOR will be continued. The ability to generate Lerwick developing climate models, allowing researchers forecasts decades in to the future will help in to look at the present state of Atlantic circulation, many ways: from being better prepared for its natural variability and predicting its future extreme events such as fl ooding or heat waves, development. to ensuring that we manage our use of the marine FLOW PATHWAYS environment sustainably. Atlantic inflow The project’s key fi ndings were: Deep overflow One focus of NACLIM is to explore the OBSERVATION ARRAYS • We need a good knowledge of the state of the predictability of the marine ecosystem on Atlantic inflow observations North Atlantic circulation as a pre-requisite these longer time scales. This is a tremendous Dense overflow observations for reliable decadal climate forecasts. challenge: our understanding of the linkages Water mass transformation observations • Circulation in the Atlantic has been stable in between physical and biological variability is the past decades, but there is evidence that it CIRCULATION OF THE NORTH ATLANTIC SHOWING LONGTERM OBSERVATION EFFORTS still basic compared to our understanding of the ADAPTED FROM THE THOR PROJECT. can react to external changes over short time drivers of the variability in the North Atlantic periods (just decades). basin and its impact on our climate. Climate North Atlantic Circulation • Although there is a risk that something might change will have far reaching effects, and we Have you ever noticed that Lerwick-residents The water from the North Atlantic enters the happen to the Atlantic circulation in future, are now starting to explore the predictability of enjoy quite a mild climate despite being at a Norwegian and Greenland Seas (Nordic Seas) we can be quite sure that a collapse of the biological variability and how we will manage our similar distance from the equator as Anchorage through three pathways (see above): thermohaline circulation will not happen marine ecosystem under these new conditions. (Alaska) and Magadan (Siberia) (see graph over within the next ten years. The research leading to these results was funded by the page)? It’s because Lerwick sits on the edge of 1 an infl ow of Atlantic water through the • We need to continue to observe the Scottish Government, as well as by the European Union the North Atlantic basin. Faroe–Shetland Channel (between Faroes and circulation, in order to develop an early- 7th Framework Programme (FP7 2007-2013), under grant Shetland); warning system and to allow society time to agreement n.212643 (THOR, http://www.eu-thor.eu) and The North Atlantic Basin develop adaptation strategies. n.308299 (NACLIM, http://www.naclim.eu). This document 2 the Faroe Current crosses the Iceland–Faroe refl ects only the author’s views and that the European Union In the North Atlantic, warm salty water fl ows Ridge (east of Iceland); and is not liable for any use that may be made of the information northwards at the sea surface and the transfer Marine Scotland’s work in the Faroe Shetland contained therein. of heat by the ocean and the atmosphere 3 Channel contributed to the THOR Observational the North Iceland Irminger Current fl ows provides Northern Europe with a milder climate Programme (see “Our latest results” box). polewards in the eastern Denmark Strait than similar latitudes of other ocean basins. (west of Iceland). www.youtube.com/marinescotlandvideo www.gov.scot/marinescotland www.fl ickr.com/marinescotland blogs.gov.scot/marine-scotland/ © CROWN COPYRIGHT MARINE SCOTLAND 2016 @marinescotland 20 Observing ocean circulation Our latest results 15 Since the mid-1990s, scientists have observed The latest results from the observations made by swimming pools (i.e. 7.0 x 106 m3) enter 10 C) 1990-1999 o the overturning circulation in the North Atlantic Marine Scotland in the Faroe Shetland Channel the Nordic Seas every second across the 5 at key locations on the Greenland-Scotland (FSC) are: Greenland-Scotland Ridge. 0 Ridge, using state-of-the-art techniques that • On average, every second approximately • The estimated transport (amount of water -5 complement the more traditional measurements 1,100 Olympic-sized swimming pools and energy) is not constant. Instead, -10 carried out since the end of the 19th century. 6 3 complex variations in the currents mean Anchorage – 61o 11' 31" N 149o 45' 44" W of Atlantic Water (i.e. 2.7 x 10 m ) fl ow o o They deploy temperature and salinity sensors -15 Magadan – 59 33' 00" N 150 48' 00" W patches of energy travel through the region Lerwick – 60o 09' 15" N 001o 08' 55" W northwards into the Nordic Seas through the Mean Monthly Air Temperature ( and profi ling current meters, allowing them to -20 Faroe Shetland Channel. When combined with from the Atlantic (also called meso-scale Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec better estimate the volume of water leaving Month the Atlantic Water transported East of Iceland eddies) introducing variability. the Nordic Seas in the deep cold overfl ows, and MONTHLY MEAN AIR TEMPERATURE, IN °C, IN THE 1990S and across the Iceland-Faroe Ridge: 2,800 • The deployment of only four current AS OBSERVED IN ANCHORAGE ALASKA, MAGADAN the amount of surface Atlantic water fl owing 5.5 meters across the FSC is insuffi cient to /s) SIBERIA AND LERWICK SHETLAND. poleward at the sea surface. 3 5.0 monthly mean value capture all the dynamics of the Atlantic smoothed annual 4.5 water transport, but we can combine the In 2004, a British-American collaboration saw Within the Greenland Sea, the relatively saline 4.0 observations with satellite based altimetry the start of a monitoring array further south Atlantic waters lose their heat to the atmosphere 3.5 (sea surface height) measurements to obtain across the North Atlantic at 26°N. and cool. This makes them suffi ciently dense 3.0 an almost 20-year time series. (heavy) to sink to the deep, fi lling the deepest 2.5 • So far, there is no signifi cant long term parts of the Greenland and Norwegian Seas. This What is the role of Marine Scotland in observing circulation in the North 2.0 change in the amount of Atlantic water formation of deep water in turn draws more 1.5 Atlantic? fl owing into the Nordic seas, but the Atlantic water northwards into the Nordic Seas 1.0 temperature and salinity of the Atlantic The Marine Laboratory in Aberdeen has a the Faroe Shetland Channel (in millions of m across the underwater Greenland–Scotland Ridge Volume Transport of Atlantic Water observed in 0.5 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 water have increased since the early 1990s. and the deep cold water masses fl ow towards the long history of making observations in one • Our observations are a small but essential equator, channelled through narrow gaps in the of the three important gaps in the Greenland- OBSERVATIONS OF THE QUANTITY OF ATLANTIC WATER FLOWING contribution to large EU research projects underwater ridge. Scotland Ridge - the Faroe Shetland Channel. POLEWARDS THROUGH THE FAROE SHETLAND CHANNEL: THE This region is also key for commercial fi sheries LARGE VARIATIONS FROM MONTHTOMONTH AND BETWEEN YEARS on climate variability and its impacts on HIGHLIGHT THE ENERGETIC CIRCULATION OF THE NORTH ATLANTIC. society. This circulation is called the Atlantic Meridional and oil exploration. Since the late 19th century, Overturning Circulation (AMOC) and forms part of researchers from Aberdeen have made regular the ‘great ocean conveyor belt’. Also, it is of global observations of the vertical temperature and signifi cance in the Earth’s climate system. salinity structure in the Channel. In collaboration with scientists from the Faroe Islands (Faroe Why is it important? Marine Research Institute) and Norway (University of Bergen), Marine Scotland also In 2005, some observations suggested that the started monitoring the velocity of the surface AMOC was slowing down, raising concerns that water fl owing through the Faroe Shetland a breakdown of this circulation would have Channel, by deploying vertically profi ling signifi cant impact on the oceanic heat supply to current meters which are moored near the sea Europe’s climate. Since then, more measurements bed, measuring towards the surface. Together and computer simulations have been made to with temperature and salinity observations help better understand the changes that were made during regular ship surveys, these data observed, to understand what drives the AMOC can be used to calculate the amount of Atlantic and how and why it varies naturally. water entering the Nordic Seas through the PROFILING CURRENT METERS READY FOR DEPLOYMENT IN THE FAROE SHETLAND CHANNEL. Faroe Shetland Channel and the amount of heat THE WATER SAMPLER AND INSTRUMENTATION READY TO COLLECT and salt it carries polewards. A PROFILE OF THE WATER COLUMN PROPERTIES, SUCH AS TEMPERATURE AND SALINITY..
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