The science and the weather ramp up

We’re heading east, a bit slower than before, but we are making good time.  The waves have come up a bit and the science is in full swing.  There are hundreds of measurements being made each hour, with countless continuous measurements of the ecosystems and physical environment, ranging from ocean properties to aerosols and clouds.

The wind has come up a bit and we are on tail end of a storm.  We will be following the storm for the next two days, but luckily we move at 11 knots and the storm is much faster.  Nevertheless, we expect 30 foot (10 meter) seas tomorrow.  I took a short video of the back deck today before the seas came up and they had to limit our access to avoid anyone being washed off the deck.  At the time the video was taken, the seas were no larger than about 15 feet (5 meters).  I have a bet going with some of the crew that the incubators (the plastic water filled boxes seen strapped to the deck on the video) won’t make it until morning.

 

A normal day on the North Atlantic aboard the R/V Atlantis from Peter Gaube on Vimeo.

For a more “human” perspective on the research and people aboard, follow Nicole’s blog. Nicole is a reporter who decided, last minute, why not spend a month in the middle of the North Atlantic, in November.

On the Shelf

We’ve left port and are steaming east, northeast towards our first station. We will be cruising along the shelf at 11 knots for the next few days.

Our first station will be in an anticyclonic eddy near 50 degrees N (this is eddy A1 in the map below).

Map of our cruise and track and eddies.

Map of our cruise and track and eddies.

It’ going to take us another 6 days to get there. During the transit, samples are being continuously analyzed from the through-flow system which takes sea water from just below the surface and pumps it through a multitude of instruments.

chogram
We have also started to collect acoustic data using the ship’s acoustic doppler current profiler (ADCP). Although this is an echosounder that is designed to measure ocean currents, but I’ve also been looking at the amplitude of the acoustic backscattering in the water column. Yesterday around sunset, we observed the vertical migration of zooplankton and micronekton (little beasties that eat smaller beasties and plants) to the surface. It was exciting to watch this unfold in real-time.

At the same time, we started to see these little critters in the imaging flow cytobot.

ifcb

Check back in a day or two and I’ll post a short video giving a tour of the ship, our home for the next month.

Preparations

Preparations are under way for the first cruise of the NAAMES field program.  We will be leaving from Cape Cod, MA, on November 5th to conduct a 30-day cruise into the North Atlantic.  Our mission is to characterize the marine ecosystem, from viruses to phytoplankton and all the way to mesopelagic fish, with the goal of quantifying the links between ocean variability (seasonality, eddies, and fronts), marine ecosystems and aerosols.  We will be on board the R/V Atlantis, a  142-foot, steel-hulled research vessel operated by the Woods Hole Oceanographic Institution.  Our cruise will take us from Massachusetts, up to about 48 degrees north, and then down along 41 degrees west to approximately 38 degrees north (see planned cruise track below).

The planned expedition path overlaid on satellite estimate of the April mean climatological chlorophyll-a concentration. The NAAMES program time line is shown along the bottom of the figure with blue triangle indicating planned cruise dates.

My primary research goals on this cruise will be to help guide the ship into mesoscale eddies using real-time satellite data.  I will also be deploying 20 surface drifters that we will use to study the movement of the eddies and help guide the NASA C-130 aircraft to fly over and sample the eddies.  In addition, I will be collecting multi-band acoustic observations to characterize deep scattering layers, layers of fish and squid below the sun-lit surface layer of the ocean (what is often called the “Twilight Zone”) inside and outside of the eddies.  This research is motivated by recent observations of the use of eddies by white sharks.  We have observed that sharks dive deeper and longer in anticyclonic eddies when compared to cyclones (more info here).  Our hypothesis is that this is because deep scattering layers, where the sharks are feeding, are deeper and have higher biomass in anticyclones than cyclones.  I will try to post semi-regular updates during the cruise, so please come back and see what we are doing in the coming weeks.

You can see where the ship is here.

DSL_schematic

Schematic representation of isopycnal surfaces (thin black curves), white shark dives (wavy black arrows) and the DSL (pseudo-color) in (a) anticyclonic and (b) cyclonic eddies. The detection of the DSL by ship-board acoustics is indicated by the cone of solid downward propagating waves with the returned signal indicated by dashed upward propagating waves.

Lydia swims 100 miles in less than 2 days into the core of a large anticyclone

Two days ago I reported that Lydia swam towards a large anticyclonic (clockwise rotating) eddy or meanders (see post here).  She approached this anticyclone and swam northeast along its periphery.  In the past 24 hours, Lydia has turned southeast of the previous anticyclone and has entered into the center of an adjacent anticyclonic eddy!  Analysis of her interaction with eddies during her trip offshore in the summer and fall of 2013 (find more info here) suggests that she prefers the cores of anticyclones over cyclones and makes repetitive deep dives (often over 800 meters) while in the cores of anticyclones.  Her activity in the past few days suggest that she might be honing in on some cues, be they potential prey, mates, or other, and is occupying the core of yet another anticyclonic eddy.

Lydia's track overlaid on a map of sea level anomaly. Anticyclonic eddies and meanders are shown as orange and red features, cyclonic eddies and meanders and blue and purple features.

Lydia’s track overlaid on a map of sea level anomaly. Anticyclonic eddies and meanders are shown as orange and red features, cyclonic eddies and meanders are blue and purple features.

This begs the questions: Do white sharks seek out anticyclonic eddies because they are areas that concentrate prey and/or potential mates, or do they prefer the warm water found in anticyclones while swimming elsewhere?  We’ll keep a close eye on where Lydia goes from here and hope to be able to address these questions in the future.

Has Lydia found a new eddy?

There has been lots of excitement recently about Lydia, an approximately 2,000 lbs. white shark, and her recent eastward movement offshore towards a region populated with large Gulf Stream eddies. Until yesterday, Lydia was moving mostly due east. But now, she has taken a sudden turn north. To investigate if her change in course could be cued by the presence of a particular eddy, I overlaid her track on a map of near-real time SSH (data from http://eddy.colorado.edu/ccar/ssh/nrt_global_grid_viewer).

Sure enough, her turn to the north puts her in the region of a large anticyclonic (clockwise rotation) eddy or meander, characterized by warm water low in chlorophyll (algae).  We’ll have to see where she goes next to find out of she decides to stay in this eddy, or keeps moving north-northeast.

Lydia's track (starting Nov 4th and ending Nov 24th, 2014) overlaid on a map of sea level anomaly (often referred to as SSH, sea level height).

Lydia’s track (starting Nov 4th and ending Nov 24th, 2014) overlaid on a map of sea level anomaly (often referred to as SSH, sea surface height).  Track data courtesy of ocearch.org and SSH data of the Colorado Center for Astrodynamics Research (CCAR).