Category Archives: News

In my old bedroom at my parents’ there is a framed cloth with my name and birthday embroidered in thread. Around the border, there are ducks. They are floating on a blue, cartoon-style wave.

Susan Lozier made it for me when I was born. Now, she’s sending me to sea.

In case you’re new here (like me): Lozier is an oceanographer at Duke, and one of the scientists leading OSNAP. The acronym stands for Overturning in the Subpolar North Atlantic Program.  The “overturning” refers to a sort of conveyor belt of water:  the sun warms water at the equator, some of it flows north past Iceland where it drops off its heat, sinks, cools, and then makes its way south. (See the arrows in OSNAP’s cartoon logo? That’s the general idea). This Atlantic heat-shuttling keeps Europe on the whole cozier than it would be if it were sitting its own stagnant bath tub, instead of the same body of water as the rest of the whole wide world. And, of course, human-cause climate change will alter this process — though scientists are not certain of exactly how.

 So, starting this summer OSNAP — a multi-country endeavor, over a decade in the making — is setting up what oceanographer Bob Pickart calls “a giant picket fence” across the ocean. This — a collection of stationary instruments, floats, and gliders — will be  a check point across the North Atlantic for water as it makes its way north, and then south.  Pickart, who works at Woods Hole Oceanographic Instituition, is another leader of OSNAP’s US arm — and importantly, he is the lead scientist on the R/V Knorr for the month of August (Lozier is spending the summer on land at Duke).

We are on this boat for a month to deploy Pickart’s section of the fence: 8 strings of instruments up to 3 kilometers deep, that will be weighted to the ocean floor. These are called “moorings,” and their purpose is to track the underwater highways of flowing water. Each mooring, with its heavy hardware and smart gadgets, has a $200,000 price tag. We’ll be carefully placing them near the southern tip of  Greenland, where they will spend two years alone, collecting data, which Pickart and a new team will retrieve in 2016. On our journey to drop off the moorings, we’ll also make 50 pit stops to take quick stats on the ocean at various depths. These pit stops will happen whenever we arrive at a designated pit-stop location — so we’ll be throwing sensors into the ocean at all hours of the day and night.

Well, Pickart and an assortment of students are here to do all that. I’m here to observe.

For my part, I grew up to be a writer. I’m based out of my office (a corner of my living room) in Philadelphia, where I write and fact check for magazines and websites. I’m a freelancer, which means I can temporarily re-locate wherever I please. The OSNAP grant is comping my room and board for a month, in exchange for the open-ended challenge of conveying the project to the greater world via this here blog.

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Four Decades of Weather and Climate at the Scottish Association for Marine Science Laboratory on the Dunstaffnage Peninsula in the Scottish West Highlands (1972 to 2014)[1]

Stuart Cunningham, 29^th July 2014

“Of mice and men” stated that the arguments about the causes of climate change are settled (in the same way we no longer argue whether the Earth orbits the sun): climate is changing and it is our doing. Practically we need to focus more on the regional impacts of climate change. The OSNAP programme will provide such a focus. This article describes some regional climate – in the west highlands of Scotland, linking this to global climate teleconnections and climate change. We then describe briefly how OSNAP contributes to new knowledge and understanding of how regional climate and wider climate patterns can be linked.

Within the grounds of the SAMS marine laboratory, at Dunstaffnage, the UK Meteorological Office maintains a synoptic weather and climate station. Operating continuously since 1972 we can now investigate climate at this site over four decades. What does it show about the weather and climate in the west highlands of Scotland?

The seasonal cycles of air minimum and maximum temperatures, rainfall, sunshine hours and air-frost days (Figure 1, Table 1) have clearly defined seasonal variations. Our summers are warmest in July and August, but sunniest in May, and notably dry in April, May and June. Overall, we have a wet climate, with an annual average rainfall of 165 cm (5 feet 5 inches for the imperialists amongst you!). But the variability of our weather (and the beauty of our geography) gives a special meaning to fine days. Alastair Reid’s poem “Scotland” perfectly captures the mood swings of the Scottish psyche induced by the Scottish climate (and the Calvanism). For your edification the poem is reproduced at the end of this blog.

Climate Trends

We will look now at long-term weather trends of temperatures and rainfall (i.e. the climate). These two variables have quite different patterns of change over four decades, nicely illustrating the complexity of climate.

Temperature

The singular striking aspect of the temperature anomalies at Dunstaffnage (Figure 2) is the pattern of cold anomalies between 1972 and 1995, which are completely reversed to warm anomalies between 1995 and 2010. A linear trend shows a warming of 1.08°C from 1972 to 2014. Shown in the plot are the 95% confidence limits for this trend.

How does this local temperature change compare to global average temperature changes? Over Earth’s land and ocean surface the average temperature is increasing rapidly: the warming (by linear trend) from 1972 to 2014 is 0.8°C[1]. Most of the observed increase in globally averaged temperature since the mid-twentieth century, is very likely due to a 40% increase in atmospheric carbon dioxide concentration since the pre-industrial era[2]. Dunstaffnage temperatures have risen by 1.08°C, therefore increasing at a rate 26% higher than the global average. Quite possibly this more rapid warming at Dunstaffnage (56.4545° N, 5.4379° W) is linked to the amplification of warming at high latitudes due to decreasing ocean ice cover (amongst a host of other potential feedbacks). Changes in northward heat transport by the oceans and moist atmosphere could also be implicated.

In the last decade global average temperatures have remained constant or decreased slightly, and this is reflected in decreasing temperatures after 2007 at Dunstaffnage (Figure 2). This temperature stand does not mean an end to global warming, but is explained by natural climate variations: large cyclic variations in North Pacific winds[3] have increased heat absorption by the ocean, leading to steady atmospheric temperatures. We have not demonstrated a link between temperatures in Dunstaffnage and atmospheric variability in the Pacific, but it is probable.

Therefore at Dunstaffnage the long-term temperature trend strongly links to the global warming trend and to effects of preferentially increased warming rates at high latitudes. We also see evidence for remote effects of natural cycles of Pacific climate variability in the stand of warm temperature anomalies in the past decade.

 

 Rainfall

One difficulty with analyzing rainfall data is the large inherent variable. This is readily seen in Figure 2, as the large variation around the mean value in each monthly mean value of rainfall (the grey bars are large): it can be wet or dry at any time of the year with large variations around the seasonal (expected) value.

At Dunstaffnage (Figure 3) there is an approximately five-year cycle of wetter and drier periods (particularly since the mid-1990s). The long-term trend from 1972 to 2014 suggests a net increase in annual rainfall of 13 mm (3.1 mm/decade), but statistically this trend is not significant. Our inability to identify long-term trends of observed rainfall is a typical problem for the majority of global rainfall observations.

As an aside, a warming atmosphere holds more water vapor, the content increasing approximately 7% for one degree of warming. The oceans dominate the fresh-water cycle, evaporating 13 million cubic meters of water per second and receiving 12 million cubic meters of water per second in rainfall. The small difference of 1 million cubic meters per second falls as rain over the land. Changes in pattern and amounts of rainfall over the ocean change the oceans’ salinity and thus observations of ocean salinity can tell us about changing precipitation (the ocean rain gauge) – even if trends in rainfall are hard to detect by direct observation over the land.

Although rainfall at Dunstaffnage is an inherently noisy process we can relate it to the main pattern of atmospheric variability in the North Atlantic called the North Atlantic Oscillation (NAO). The atmosphere in the Atlantic has a high pressure centered over the Azores and a low pressure centered over Iceland. The atmospheric pressure difference from the Azores to Iceland strongly controls the direction and strength of weather patterns – the westerly trade winds – that travel from west to east across the Atlantic. When the pressure difference between the Azores and Iceland is larger than normal then storms tend to pass eastward at higher latitudes than normal (north of the UK in extreme cases). This leads typically to wetter (and warmer) conditions over west Scotland. Conversely, for a lower than normal pressure difference, storms track eastward at much lower latitudes, bringing rain to Spain: and dry (and colder) conditions to the west of Scotland.

Comparing rainfall at Dunstaffnage to the North Atlantic Oscillation Index (Figure 4), there is evidently some relationship: often the red (high NAO index/high rainfall) and blue (low NAO index/low rainfall) correspond. While the correspondence is not one-to-one, the variations in the NAO index explain 44% to 57% of the signal in Dunstaffnage rainfall (range is 95% confidence interval). Thus Dunstaffnage experiences rainfall patterns that are strongly related to the latitude at which the west to east moving storms cross the Atlantic.

We can extend our comparison of Dunstaffnage rainfall and the atmospheric variability over the Atlantic by thinking how the North Atlantic Oscillation and rainfall changes accumulate over time. That is do drier or wetter patterns persist for many years? To examine this we simply add the rainfall anomalies with time and do the same for the North Atlantic Oscillation Index (Figure 5).

From 1972 to 1986 Dunstaffnage became progressively drier with time (Figure 5). This makes sense looking at Figure 4 where these years have negative rainfall anomalies. Then we enter a wetter period from 1986 to a peak in rainfall accumulation in 1995. Since then Dunstaffnage is trending towards drier conditions, but with the 5-year oscillation evident. The accumulated oscillation index (Figure 5) corresponds closely with the rainfall accumulation. The oscillation index explains 67% to 75% of the signal in accumulated rainfall (at 95% confidence limits). This correspondence between the rainfall and the oscillation index is entirely expected. Hundreds of scientific papers have established links between the oscillation and multiple climate variables: analysis includes both modern data and paleo-climate data, establishing that this pattern has been active for at least 5000 years.

 

Discussion

At Dunstaffnage we can link local temperature and rainfall variability to patterns of established climate variability: rainfall to the North Atlantic Oscillation; temperatures to the Pacific Decadal Oscillation. We can also identify the global warming temperature trend at Dunstaffnage and find that it is larger than the global average temperature rise: we suggest this is related to more rapid warming that happens at higher latitudes.

Regrettably, I have falsified the title of this article “‘Dinnae expect onything an ye’ll no be disappointed”, by demonstrating that by examining data around the globe can tell us with some confidence what to expect, both for long-term temperature trends and for rainfall trends.

So can we better understand these global to regional teleconnections in weather and climate patterns? The Overturning in the subpolar North Atlantic Programme is measuring the circulation in the subpolar North Atlantic because there is mounting evidence that knowing the circulation in this region leads to improved decadal climate prediction. Both modelling and observations studies link temperatures and currents in the subpolar gyre to tropical storm and hurricane frequency, rainfall in the Sahel, Amazon, western Europe and parts of the US, on wind strength and on marine ecosystems.

Thus the contribution of OSNAP to this much wider climate forecast problem is to generate new knowledge and understanding of the subpolar gyre by measuring the circulation and fluxes of heat and fresh water from Newfoundland to Greenland to Scotland. This continent-to-continent observing system will enable the relationships between circulation, ocean and atmosphere exchanges and climate impacts, for the first time, to be examined with a purposefully designed observing system.

Progress is oftentimes by small steps, but occasionally extraordinary efforts to take leap forward need to be taken.

Scotland
It was a day peculiar to this piece of the planet,
when larks rose on long thin strings of singing
and the air shifted with the shimmer of actual angels.
Greenness entered the body. The grasses
shivered with presences, and sunlight
stayed like a halo on hair and heather and hills.
Walking into town, I saw, in a radiant raincoat,
the woman from the fish-shop. ‘What a day it is!’
cried I, like a sunstruck madman.
And what did she have to say for it?
Her brow grew bleak, her ancestors raged in their graves
as she spoke with their ancient misery:
‘We’ll pay for it, we’ll pay for it, we’ll pay for it.’
Alastair Reid

View as PDF

[1] This article was written as a contribution to the 130th year of SAMS and its parent labs and also forthe centenary of Sir John Murray KCB FRS FRSE FRSGS (3 March 1841 – 16 March 1914) a pioneering Scottish oceanographer, marine biologist and limnologist.
[2] CRUTEM4 from the Climatic Research Unit (University of East Anglia).
[3] These results quoted directly from IPCC AR5, Summary for policy makers. See ahttp://www.ipcc.ch/WG1AR5_SPM_FINAL.pdf
[4] Cool phase of the Pacific Decadal Oscillation

by Stuart Cunningham, July 2014. R/V Knorr, mid-Atlantic.

“I’m truly sorry man’s dominion
Has broken Nature’s social union,
An’ justifies that ill opinion
Which makes thee startle
At me, thy poor, earth born companion
An’ fellow mortal!” – Robert Burns, 1785.

Burns writes of our interfering with the balance of nature – inadvertent or otherwise – and our short-lived sharing of the earth’s environment: in this Poem writing about the panic of a mouse and her brood with the turning of her nest by the plough’s harrow. Settled opinion is that anthropogenic forcing is the dominant mechanism driving long-term climate change: controversies now are more about our reaction to this. Long-term in this context means that over a few decades we can see the slower man-forced changes hidden amongst larger, naturally occurring climate variation. We need now to focus on the regional impacts of global warming: measuring shorter term changes so that the long term trends can be quantified. Will my home region be warmer or drier or submerged by sea-level rise? Global average change hides the nature of much larger regional changes. Observing the ocean gives us a Plimsoll line for future change, and the stimulus for better theories of oceans and the climate.

So why are we at sea?
The atmosphere and ocean transport heat from the equatorial regions to higher latitudes: this energy transfer is our climate. The atmosphere reacts quickly, while the ocean controls slower and long-term energy transports relating to our long-term climate variations. Warming and increased precipitation at high latitudes caused by global warming means that the heat transported by the Atlantic is likely to reduce over the coming century: this has long-term implications for climate patterns (particularly in the North Atlantic where the ocean acts as a “fan assisted storage heater for Europe”(1). Beginning in 2004 a purposefully designed transatlantic monitoring array began measuring the Atlantic circulation between Morocco and Miami (2). Observing the ocean is a very buy propecia online hard and expensive technical problem. Controversial in its infancy, RAPID-MOCHA blazed a trail for oceanographers: showing how by thinking big, and with cooperation between teams of brilliant scientists and with the long-term commitment of funding agencies, oceanography and climate science can tackle one of the leading climate problems in the 21st century: what controls Atlantic ocean heat transport? how is changing now: how is it likely to change in the future?; and with the ambition to forecast climate out to decadal timescales.

RAPID-MOCHA nailed the problem in the subtropical Atlantic, and so was born the ambition to install a similar purposefully designed observing system in the subpolar North Atlantic. In the subtropics we measure the maximum heat transport by the ocean. This diminishes greatly by the subpolar region: the heat lost to the atmosphere being central to climate variability for countries around the Atlantic (affecting hurricane variability, Sahel drought, Amazonian rainfall, extreme European winters, fish stock distributions). Thus OSNAP (a child of RAPID), with moorings from Newfoundland to Greenland to Scotland, aims to measure the heat transport in the subpolar region. Combining with RAPID we measure the critical Atlantic heat transport throughout the North Atlantic and the exchanges with the atmosphere. OSNAP is another milestone in our goal of building an integrated Atlantic observing network.

Man’s dominion over Nature, we now understand, is illusory. King Knut the Great 1200 years ago understood (and quite possibly demonstrated?) the futility of believing otherwise. But we can observe, theorise and understand our climate: more, better, better planned and long-term observations are the way we will make progress in understanding. Otherwise we will be unprepared for change now and for future generations. Observing the oceans is difficult but it must be done; and it will be done. This research expedition is our contribution.

1 Ellett, D. J. The north-east Atlantic: A fan-assisted storage heater? Weather 48, 118-126, doi:papers2://publication/doi/10.1002/j.1477-8696.1993.tb05861.x (1993).

2 http://www.rapid.ac.uk/rapidmoc/
https://www.rsmas.miami.edu/users/mocha/

By Amy Bower and Stuart Cunningham

Almost within earshot of the bagpipes of Scotland, we deployed the last of the 20 moorings slated for this leg of R/V Knorr Voyage 221. It was an exciting finish to this phase of the cruise. Instead of the “normal” mooring deployment strategy where we pay out the top of the mooring first and finish with the drop of the anchor, we lowered a single instrument to within one meter of the sea floor on a heavy wire, and then sent an acoustic signal to release the instrument and let it drop to the bottom. It is an upward-facing Acoustic Doppler Current Profiler (ADCP), which will constantly emit sound signals up to the sea surface and use the Doppler shift of the return signals to measure the currents from top to bottom. As described in a previous post by technician Karen Wilson, the ADCP is encased in a trawl-resistant frame (which our Scottish colleagues call “the Spaceship” for obvious reasons) so that fishing gear pulled along the sea floor will roll over the cage and not snag it.

The exciting part of the deployment was the final approach of the Spaceship to the sea floor. No one can see with their eyes what is happening 400 meters down—so we “see” with our ears, relying on sound signals from the Knorr and from the Spaceship to tell us how close to the bottom it is. The goal was to not release the frame until it was within a few meters of the seafloor. If we release it too early, it could flip upside down before it hits the bottom. If we hold on too long, the package might slam into the bottom and be damaged. And remember that the ship is rolling a bit, which lifts the frame up and down slightly with every swell. After much suspense, Principal Investigator Stuart Cunningham “pulled the trigger” and the frame dropped to the sea floor. Next year we will return to this site to recover the instrument and its precious cargo—the first long-term continuous measurements of the shelf edge current off Scotland.

Now the science crew is changing gears from mooring to CTD operations. For the rest of the cruise, we will be slowly making our way back along the same cruise track, stopping every so often to lower the CTD package to the bottom in order to measure the temperature, salinity, dissolved oxygen content and other seawater properties. A pair of ADCP’s mounted on the CTD package will also record the ocean current profile at each station. These stations will be spaced much more closely together than the moorings—this will give us the opportunity to get an initial high-resolution snap-shot of all the currents and water properties along the OSNAP line to compare with the measurements from the moored instruments.

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by Bill Johns

Today marks a week at sea on our cruise aboard the R/V Knorr, and things have been going quite well up to this point. We have settled into a routine of deploying two moorings per day as we lay out the combined Dutch/U.S. mooring array across the Reykjanes Ridge. Each day begins with a mooring deployment just after breakfast, then a steam to the next site (usually 20-30 miles away) and an afternoon deployment, and then we spend the night running ahead to the next two sites to perform bottom topography surveys so we can pick spots for the moorings to be deployed the next day.

Fortunately, the R/V Knorr has a multi-beam echo sounding system called Seabeam that measures the bottom topography along swaths perpendicular to the ship’s motion. These swaths have a width about 3 times the water depth, so this allows us to paint a picture of the bottom topography for several miles to either side of the ship. Without it, we would have to steam a grid pattern with the ship to get a two-dimensional view of the bottom, a very time consuming task. (Think of it as running order klonopin a paint roller over the bottom instead of drawing a single line with a pencil.)

Even with the Seabeam system, choosing mooring spots is not trivial. The bottom topography here is very rough, full of deep fractures, ridges and pinnacles that are characteristic of the newly-formed earth’s crust near mid-ocean spreading centers, which is what the Reykjanes ridge is; it is the northern arm of the great mid-ocean ridge system in the Atlantic Ocean. Finding a good spot for a mooring involves several factors, but one of the most important things is that it needs to have reasonably constant depth over an area that we can be sure to land the anchor in.

For the uninitiated, deploying a mooring consists of first streaming the whole mooring out behind the ship, starting from the top of the mooring that will be nearest the surface. Instruments and floats to support them are then added at various lengths along the mooring wire as the ship slowly steams toward the deployment site from some distance away. The last thing to be attached is the anchor, which is then lifted over the side and let go when the target spot for the mooring is reached. Actually the ship usually steams a bit past the target site before the anchor is released, because as the anchor sinks it drags all the mooring components laying on the surface toward it, causing the anchor to literally swing backward as it sinks rather than falling straight down. This is called “fall back”, and especially for very tall moorings it needs to be factored in. (And we are talking heavy anchors here, usually a few thousand pounds, that are made up of cast iron, or scrap railroad wheels, or leftover heavy anchor chain from large ships; each group onboard has their own favorite style of anchor.) Also, ocean currents can move the whole mooring horizontally as it falls, and since it can take up to a half an hour or so for an anchor to reach the bottom, this can also affect the landing spot. So, there is always some uncertainty in exactly where the anchor will wind up on the bottom, and even those with lots of experience can seldom place an anchor within a tenth of a mile of the target site in full ocean depths. That is why we try to find flat spots to land the anchors in. And these can be very hard to find along the Reykjanes Ridge!

Why is hitting the target depth so important? Mainly it is because the moorings are designed to measure currents or water properties at specific depths, and the instruments will miss those depths if the mooring winds up where it is deeper or shallower than the mooring was designed for. Also, some of our moorings have instruments very near the surface, up to 50 m from the surface. If we land the anchor at a depth that is 50 m shallower than planned, then those instruments will be laying at the surface and can be damaged by surface waves or be run over by ships. If we miss too deep, then the instruments are not measuring the near-surface properties we want to observe. (Note that all the moorings we are deploying are “subsurface” moorings, meaning that they have no surface buoy and lie completely below the surface. We retrieve them by sending coded sonar commands to a device called an “acoustic release”that releases the rest of the mooring just above the anchor, and it is then recovered when it floats to the surface.)

So far we have been hitting our target spots pretty well, and this is something that requires excellent coordination between the scientists, the deck crew, and the bridge officers driving the ship. How do we know if we hit our targets? By transmitting sonar signals to the acoustic releases on the bottom, we can triangulate on them and determine precisely where they landed.

By now we have deployed 10 moorings, exactly half of the total number of moorings we will deploy in this cruise. On these moorings are countless instruments measuring currents, temperature, and salinity at depths from near the surface to the bottom.

While we are out on deck adding components to the moorings as they are streamed out (which can take several hours for each one), there is sometimes an opportunity to look around at the sea and take in the ocean vista. This is especially true for me, since I am usually just standing back and taking notes as others do all the hard work on deck. For the last few days I have been noticing especially the birds. First of all, there are an amazing number of sea birds out here. Ever since we have left Reykjavik, one can see birds from horizon to horizon, darting about just above the waves. I am used to seeing sea birds, but in the tropics and subtropics, where I have done most of my field work, they seem to be much more scattered and are seen only occasionally. Here they are everywhere, and it boggles the mind to think of the vast number of birds that must be out here. They are mostly Northern (or Arctic) Fulmars, which look like a very stout seagull with a trimmer tail.

Whenever we stop the ship to work, they flock to us in the hundreds and set down on the water behind the ship, waiting expectantly. Of course, they think we are a fishing vessel, and they are hoping for some morsels of by-catch. I can almost hear what they are saying to each other: “What poor fisherman these people are!” “I have been following this ship for 4 days now and haven’t yet gotten a single scrap to eat!”. It is amazing to think how we have impacted their existence, and how they have learned to follow ships for an easy meal in the years since we humans began setting out to sea (or is it even in their genes now?). Perhaps in their next stage of evolution they will learn to recognize a research vessel from a fishing boat!

Tonight is the World Cup final, and all of us who are not on watch will be huddled around the radio listening to it. Unfortunately the Dutch team did not make the final, but they had a brilliant cup, culminating in a third place victory over Brazil, and our Dutch colleagues onboard certainly have much to be proud of.

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By Amy Bower

As described in earlier posts, the purpose of OSNAP is to quantify the ocean’s role in redistributing heat and fresh water between low and high latitudes in the North Atlantic. The “overturning circulation” refers to the generally northward flow of warm and salty water in the upper ocean, and the southward return of colder, fresher water deeper down. The system of ocean currents that makes up the overturning circulation has been efficiently depicted in various schematic diagrams and is often referred to as the Great Ocean Conveyor. It is important however not to interpret this schematic as exactly representative of the deep and shallow currents in the North Atlantic. A more realistic view is shown by the second diagram below, but even this suggests overly smooth and well-behaved current pathways.

As a complement to measurements of temperature, salinity and currents at fixed locations along the OSNAP line, OSNAP co-PI Susan Lozier and I will be releasing a total of 120 freely drifting floats into the deepest currents in the subpolar North Atlantic to document the real pathways of these slow but relentless “rivers” of near-freezing water flowing along the bottom of the ocean.

So how do we track the pathways of currents two miles deep? We take advantage of the fact that sound travels exceptionally long distances in the ocean. The first step we are taking is to moor 10 sound beacons throughout the subpolar region where we plan to release the floats. A map of the beacon locations is shown below. Each beacon is anchored to the sea floor in such a way that it is suspended in the water about 1200 meters down from the surface. At a precise time each day, the beacons emit an 80-second tone at about 260 Hz. Then we release floats from the research vessel at various locations where we know the currents are located. The floats have just the right weight (measured within 1 gram) to sink and drift 200 meters above the sea floor. Attached to each float is an underwater microphone, called a hydrophone. The floats will listen for the beacons and record the time that they hear the sound signals. They will do this for two years, then drop some weight so they can rise to the sea surface and transmit the recorded information to us via satellite. Knowing the time the signal was sent, and each time it reached the float and the speed of sound in seawater, we can figure out the distance between the float and each sound beacon. As long as the float hears signals from at least two beacons, we can figure out where the float was every day. By connecting the dots from day to day, we end up with the float’s trajectory and the path of the water it was drifting with. With many floats, we can generate a description of where the currents go most frequently. We can also observe meanders and eddies in the currents.

On the first leg of the R/V Knorr’s OSNAP voyage, three of the beacons (8-10 in the map above) and 10 of the floats were deployed. Some test floats released at the same time have already surfaced and let us know that those three beacons are working properly. Our first success! Yesterday, we anchored sound beacon #5 in the Irminger Basin, west of the Reykjanes Ridge (see photos below). Next week we will moor #6 and #7, and release 10 floats east of the Reykjanes Ridge. Altogether it will take four research cruises on two different vessels to get all 10 beacons and 40 floats in the water this summer. We plan to rlease 40 more floats each in the summers of 2015 and 2016. It’s “Bon Voyage” to each one as it goes off for a tour of the deep currents of the North Atlantic.

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by Bill Johns

After much anticipation and seemingly endless planning, we finally set off from Reykjavik, Iceland at 0900 last Sunday morning (July 6th) on Leg 2 of the R/V Knorr’s summer 2014 OSNAP field campaign. Luckily the sea conditions were much improved from what they had been for the last few days offshore of Reykjavik. During the cruise mobilization and loading days a low pressure system had planted itself over Iceland, and the strong winds on its back side brought unseasonably cool temperatures to Iceland and a big swell outside the harbor. This had all of us (and especially the rookies) dreading what might lie ahead. Fantastically the sun came out before departure and the winds laid down a bit, and we found ourselves running SSW toward our work area with a nice following sea on the starboard quarter and the wind at our back, out of the north at about 20 kts.

Onboard are an international group of scientists from the U.S. (University of Miami, Woods Hole Oceanographic, and Duke University), Holland (Royal Netherlands Institute for Sea Research), and the U.K. (Scottish Association for Marine Science). Our main goal for this trip is to lay out a large string of deep-sea moorings that carry arrays of instruments measuring currents, temperature and salinity, across a swath of ocean extending from Scotland to the eastern Irminger Sea. We will also be deploying some floats that drift below the surface and track themselves by listening to sound-emitting sources we are placing on some of the moorings.

Each of the groups onboard has brought with them lots of equipment, probably enough to legitimately have their own cruise, but we have thrown ourselves together to maximize efficiency. That means the ship is very heavily loaded, and although I have used the R/V Knorr myself on a number of large previous expeditions, I have never seen her so packed to the gills buy aciphex online with equipment. There is something in every nook and cranny of the deck and laboratory spaces. We will be deploying twenty (20!) deep-sea moorings on this cruise, which may well be a record number of moorings on one cruise (somebody should go look that up). The Knorr is an incredibly capable vessel. She is due to be retired later this year, and I will miss sailing on her.

Of course, on this cruise we are focused on two things: (1) carrying out our deployment and sampling operations as efficiently as possible, and (2) the World Cup! On the night before departure we watched the game between Holland and Costa Rica at a venerable establishment in Reykjavik called the “Dubliner”, and helped our Dutch colleagues root their team to victory, in a nail biting shootout. The Dutch group is the only one onboard with a dog still in the fight, so to speak, so we’ve all decided to join their camp. Unfortunately we won’t be able to watch any more games on the ship, but the enthusiasm remains high.

The scientific work will commence shortly, and we will be deploying 2-3 moorings per day, as we move east across the Irminger and Iceland basins toward the west coast of Scotland. After all is said and done, together with coordinated deployments to be done in the next month – or already accomplished – by other international partners, we will have begun our 4-year program of continuously measuring the meridional overturning circulation and associated heat and freshwater fluxes by the ocean across a complete trans-basin section from Labrador to Scotland. This program will ultimately help to determine what causes changes in the heat carried by the oceans to the Arctic and sub-Arctic regions, and how this may impact future warming and climate change in the north Atlantic region and globally.

Now… when is the next World Cup game??

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By Susan Lozier

Though thousands of miles from the Labrador, Irminger and Iceland seas, where all the OSNAP action is taking place this summer, I can almost feel seasick at times reading the emails from my students and colleagues at sea. Admittedly, the chances of actually getting seasick in the comfort of my office here at Duke University are slim, so this summer I can only experience that ‘pleasure’ vicariously.

OSNAP – which stands for Overturning in the Subpolar North Atlantic Program – is a large international program designed to measure and understand the overturning circulation in the subpolar region of the North Atlantic. The overturning circulation involves the northward flow of upper ocean waters from the tropics to the polar regions and the southward, return flow of deep waters. Since the upper ocean waters are warm relative to the deeper waters, this flow pattern (poleward in the upper branch and equatorward in the lower branch) results in a movement of heat from the tropical to the polar regions. And this is why people other than physical oceanographers care about the overturning circulation: it moves heat around. And this heat redistribution impacts regional and global climate, such as rainfall and atmospheric temperatures. Just like most everything else about the ocean, the overturning circulation is variable, meaning that it changes with time. But we don’t know how large or how rapid those changes will be in the years ahead and we really don’t know what creates those changes. So, since we are quite interested in understanding how this ocean circulation will impact climate in the years and decades ahead, we have launched this new program to deploy an observing system in the subpolar North Atlantic to measure the overturning circulation. You can learn more about our program at the site www.o-snap.org.

Here is what is happening this summer:

The first OSNAP cruise started in early June aboard the RRS James Clark Ross. Filled with UK scientists led by Penny Holliday and Brian King, the seven-week (!) cruise trek runs from St. Johns, Newfoundland, Canada, across the Labrador Sea to the southwest of Greenland, around Cape Farewell and then across the Irminger Sea, the Iceland Basin, and the Rockall Trough, ending their measurements off the western coast of Scotland. Whew! The crew has maintained a fabulous blog of their journey, complete with not-to-be-missed photos. Check it out here: http://ukosnap.wordpress.com/

The second OSNAP cruise was aboard the U.S. vessel, the R/V Knorr. The Knorr left the dock at Woods Hole Oceanographic Institution on June 19th, headed to the Newfoundland basin to deploy sound sources and RAFOS floats. I was fortunate to be in Woods Hole to see the ship and Brian Guest, chief scientist, on their way. We already have some good news based on Brian’s work on that cruise. On July 6th two test floats popped up on schedule and let us know that all 3 sound sources that Brian deployed are working. Three down and seven to go!

Canadian scientists aboard the CCGS Hudson, led by Blair Greenan, left Bedford Institute of Oceanography on June 30th and as part of their work deployed three moorings along the Labrador slope at 53°N. These three moorings are the westernmost moorings for the OSNAP West line.

And just this past Sunday, 7/6/14, another OSNAP cruise got underway. US, UK and Dutch scientists boarded the R/V Knorr in Reykjavik, Iceland. Led by Bill Johns from the University of Miami, these scientists will be busy deploying moorings, sound sources and floats along what we call the OSNAP East line. See the schematic below, showing the OSNAP lines across the subpolar North Atlantic.

Finally, in early August, the scientists on the third KNORR OSNAP cruise will head back to Reykjavik to disembark and make room for the U.S. scientists occupying the fourth cruise, also on the Knorr. Led by Bob Pickart, Woods Hole Oceanographic Institution, these scientists will deploy moorings, sound sources and floats along the OSNAP West line.

When all is said and done, a fair number of instruments will have been placed in the water to measure the currents and their temperature and salinity. Though we have about two years to wait until we get the first numbers back, many OSNAP scientists will be busy working with other observational data, and also modeling data, to help set the context for our new observations when the data does start rolling in. Of course, someone has to go back out and retrieve those instruments and deploy new ones after two years. Maybe then I will get my chance for some real seasickness.

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October 18, 2013

In an effort to study the circulation of ocean waters, a key component of the global climate system, the National Science Foundation (NSF) has awarded $16 million in grants over the next five years to oceanographers at Duke University, the Woods Hole Oceanographic Institution (WHOI) and the University of Miami.

The scientists will deploy a new observing system in the sub-polar region of the North Atlantic Ocean. The five-year effort is part of the U.S.-led Overturning in the Subpolar North Atlantic Program (OSNAP).

International collaborators include researchers in the United Kingdom, Canada, Germany, France and the Netherlands. The U.K.’s Natural Environment Research Council also funds OSNAP.

“OSNAP is an excellent example of what NSF strives to accomplish,” says Roger Wakimoto, NSF assistant director for Geosciences.

“It’s an ambitious, community-driven project that builds strong international partnerships with our European and Canadian colleagues to study a complex and critical region in the climate system. It also effectively leverages NSF’s investments in ocean observing infrastructure.”

U.S. principal investigators for OSNAP are Susan Lozier of Duke University; Fiamma Straneo, Robert Pickart and Amy Bower of WHOI; and William Johns of the University of Miami.

Straneo will also direct an effort to bring together scientists focused on the North Atlantic Ocean in a virtual space where they can interact, exchange ideas and work cooperatively across international boundaries.

Called the North Atlantic Virtual InStitute (NAVIS), the project is part of a larger NSF program called Science Across Virtual Institutes, or SAVI.

The goals of the OSNAP and NAVIS efforts are to simultaneously measure surface ocean currents that carry heat northward toward the Arctic Ocean, and deep ocean currents that carry cooler waters southward toward the equator.

These currents form the overturning circulation that plays a role in redistributing heat from the equator to the poles. That overturning carries warm, shallow waters to northern latitudes and returns cold, deep waters southward across the equator.

Recent modeling studies show that a change in the strength of this circulation would have a critical effect on temperatures and precipitation in North America, Europe and Africa.

“In addition to measuring the variability of ocean overturning, OSNAP is focused on understanding what factors create those changes,” says Lozier.

OSNAP data will facilitate the study of how the northward flow of warm water affects the reduction of Arctic sea ice and the shrinking of the Greenland Ice Sheet.

“Oceanographers have known that overturning circulation is susceptible to changes in the temperature and salinity of surface waters in the sub-polar North Atlantic,” says Lozier.

“With increasing ocean temperatures, and increased ice melt that affects the salinity of surface waters, it’s important to establish how climate change might affect the strength of overturning circulation.”

The oceanographers will deploy moored instruments and sub-surface floats buy zithromax online across the sub-polar North Atlantic during the summer of 2014. The measurement period will last until 2018.

“Greenland’s margins are a great place to take the pulse of Atlantic overturning circulation in high latitudes,” says Straneo.

“This is where equatorward-flowing fresh water from the Arctic meets poleward-flowing warm Atlantic Ocean water–and where the two are progressively cooled and transformed into denser waters.

“Beneath these waters, we can also observe the equatorward flow of even denser waters formed in the Nordic Seas.”

The array of instruments will stretch along two lines, from Labrador to southern Greenland and from Greenland east to Scotland.

The instruments will provide scientists with continuous measurements of surface-to-bottom water temperature, salinity and velocity in areas of the sub-polar ocean that historically have been under-sampled.

The trajectories of sub-surface floats will offer the first look at deep-water pathways in the North Atlantic.

“This project provides the first opportunity to directly link changes in the intensity of the North Atlantic overturning circulation with the air-sea interaction processes that drive deep water formation,” says Johns.

OSNAP will be one of the first projects to make use of the NSF-funded Ocean Observatories Initiative’s (OOI) array of moored sensors that will be installed in the Irminger Sea off the southern tip of Greenland in 2014.

The Irminger Sea is one of four planned global observing sites of the OOI program, a networked infrastructure of science-driven sensor systems to measure the physical, chemical, geologic and biological variables in high-latitude and coastal ocean locations, as well as at the sea floor.

The OSNAP measurement system also complements a joint U.S.-U.K. project called MOCHA-RAPID. MOCHA is primarily funded by NSF; RAPID is funded by the Natural Environment Research Council in the U.K. Scientists participating in the project have measured the overturning circulation in the sub-tropical North Atlantic since 2004; MOCHA-RAPID has been extended through 2020.

“The OSNAP project will greatly enhance our ability to track changes in the circulation of the North Atlantic Ocean, a critical component of understanding future climate and its effects on marine ecosystems,” says David Conover, director of NSF’s Division of Ocean Sciences.

Overturning data are also critical to understanding the ocean’s continued ability to act as one of Earth’s most important carbon sinks.

Surface waters absorb heat-trapping carbon dioxide from Earth’s atmosphere. When cold, dense, southward-flowing waters from sub-polar regions sink, they carry these surface waters–and much of the carbon dioxide they contain–to the ocean’s depths, where it is no longer available to heat Earth’s climate.

“Because the storage of carbon at depth is linked to overturning circulation, OSNAP takes on added importance,” says Lozier. “A critical question for climate scientists today is: How much carbon will continue to be stored in the ocean?”

Read the NSF press release here.