Tracking Your Message in a Bottle

For centuries, sailors have written messages, corked them in glass bottles, and tossed them into the open ocean.  Drifting around the ocean gyres for years, the bottles are rarely found washed up on the shore.  Nevertheless, we were not able to dismiss the romantic idea of writing our own messages and tossing them into the ocean as we crossed the Atlantic Ocean from Cape Verde to Barbados.

Where will the ocean currents take the bottles and when will they be found?  Usually, these questions will never be answered.  But these bottles are special – they were tied to  Marine Instruments MSi satellite GPS buoys!  Graciously donated by the innovative team at Marine Instruments, the MSi buoys transmit the location of the bottles to Iridium satellites every day.  We are now able to track the bottles on a map as they drift across the ocean and place bets on where and when they may be found!

Each of the kids wrote messages, corked them into bottles, and tied them to three individual MSi drifters.  Other friends also contributed messages that were included in the bottles.  The drift path of the buoys are influenced by the ocean currents and winds.  The bottles were each deployed one-day apart with a spacing of 2.5° Longitude (146 miles at 14° Latitude, or 234 km).  The deployment locations were:

Buoy A:  15.0°N, 30.0°W
Buoy D:  14.0°N, 32.5°W
Buoy E:  13.5°N, 35.0°W

We wish to express sincere gratitude to the team at Marine Instrument for donating the buoys and providing the position telemetry service, and to Nortek Data Services for developing and hosting the website that tracks and displays the real-time map.

Click on the photo below to view a movie of Buoy A deployment!


Buoy D Deployment


Buoy E Deployment


Full Cruising World (Dec 2017) publication message in a bottle.


Click on map to view real-time buoy tracking!

Drifter Deployment

The crew of Laridae celebrated Eric’s birthday on 16 October with the deployment of the MetOcean SVP Iridium drifter.  Following a swim call in very calm conditions, the drifter was turned on and deployed overboard.  The blue dome floats above the water and measures the GPS position and communicates to shore with an Iridium satellite modem.  A thermometer measures the sea surface temperature.  Below the surface is a large sea drogue (anchor) that fills with water so that the drifter moves with the ocean currents and does not simply drifter downwind.

The drifter was deployed at location 19° 3.950’N, 22° 37.734’W (about 200 miles NNE of Cabo Verde Islands).  It reports its GPS position every one-hour and the location is mapped in real-time.  The drifter typically moves in a West-Southwestward direction with the Canary Current.  However, when the winds are light, it can sometimes be seen to make a small loop driven by the diurnal tide.  The average speed of the current is about one knot, and we will be pleased to be carried by this current as we sail from Cabo Verde to Barbados!


Laridae crew prepare to deploy the drifter.


The sea drogue slowly sinks below the water.


Click on the map to see the real-time tracking of the drifter.

Laridae crew support citizen oceanography one Secchi disk at a time

Secchi Disk Project Logo

The crew of Laridae are proud to start contributing to the Secchi Disk Project by making our own Secchi disk, taking measurements during calm periods of our passages and in many anchorages, and uploading our data to the global database using the great app.  We lowered the disk into the water until it just disappeared from sight and then we noted the depth below the sea surface that this occurred, the Secchi Depth, from the marks on the rope.  So far, the record depth measured was 26.2 m in the middle of the Bay of Biscay!

From the Secchi Disk Project: “When a Secchi disk is lowered vertically into the water the depth below the surface at which it just disappears from sight is called the Secchi Depth. The Secchi Depth measures the clarity of the seawater, which away from estuaries and coasts indicates the amount of phytoplankton at the sea surface.  By measuring the Secchi Depth you can therefore help map the ocean’s phytoplankton.

Scientists fear the population of the microscopic beings is in decline due to rising sea temperatures and, if true, that could have  consequences for every aspect of marine life. Seafarers are being encouraged to take part in a unique global study, using a Secchi disk (a simple white disk with 30 cm diameter) and a mobile phone app called Secchi to record the effects of climate change. The public science project will measure the amount of phytoplankton, minute organisms at the very start of the marine food chain, currently residing in the worlds oceans.

Construction of the Secchi disk
All members of Laridae worked together to construct our own Secchi disk.  We were able to build the high-quality, marine-grade Secchi disk for £2.99 with only a saw and measuring tape!  We found a durable, white kitchen cutting board for sale in Falmouth for £2.99.  The size of the board was exactly 30 cm x 50 cm.  This was a perfect size to achieve a 30 cm diameter Secchi disk!  Angela carefully measured and sketched the 30 cm circle on the board and the adults on the boat took turn sawing the circle out of the rectangular board.

We already had a very long length of low-stretch Dyneema line that we used for CTD casts.  We laid this line along the deck and used a tape measure to accurately mark  Secchi depth distance measurements in 20 cm increments.  Once the circle was cut and line measured, a hole was drilled in the centre to hold the measured line on the top and a weight (made from spare rigging parts!) on the bottom.

We constructed the Secchi disk after we departed Falmouth, England while we were on passage across the Bay of Biscay to Spain.  Our first measurement was conducted in the very middle of Biscay (in 4000 m water depth!) during perfect conditions; sun, calm seas, and very clear blue water.  We recorded a Secchi depth of 26.2 m.  We have continued to collect additional Secchi depth measurements at several of the anchorages that we have enjoyed in Spain.

We use the great Secchi app to upload the Secchi depth, location, and other relevant information to the group’s global database.  Anyone can view all of the data using the interactive map of Secchi depths (shown below).  For just £2.99, and a little family-fun-construction-party, you can build your own Secchi disk and start contributing to this great citizen oceanography project!


The Secchi Disk Project global database of Secchi disk measurements from citizen oceanographers.


Bay of Biscay oceanography lab

Sailing across the Bay of Biscay provided a great opportunity to experience many of the basic principles commonly taught in oceanography classes.   We used the passage from Falmouth, England to Vigo, Spain to observe the environment and sample the water like we were living in a large oceanography laboratory (and we were!).

Biscay SST Map Legend

Sea Surface Temperature (SST) of our route between Falmouth and Vigo.  The two CTD locations are noted with stars at Ushant and near the centre of Biscay.

When we departed Falmouth, the surface water temperature was a cool 14.4° C. As we sailed southwards, towards Ushant (Ile D’Ouessant) off the coast of France near Brest, the waters began to warm up. The predominate water temperature near this region was about 17° C, but the sunny conditions combined with the light winds from the south probably contributed to the slightly warmer surface layer temperature of 18° C, as measured by the RBR CTD.

The following day we dropped off the shallow continental shelf (~100 m) into the deep plateau of the Bay of Biscay with a typical depth of about 4000 m.   We were motoring across Biscay in flat calm conditions, zero wind, and full sun! These conditions are rare in the middle of Biscay, so we took advantage of the sun and calm for a swim call in the deep, clear blue waters. Following the swim call, we took another CTD cast and measured the near-surface water of about 21° C. The warm surface water, heated by the sun in the calm conditions, quickly cooled to about 19° C below a sharp thermocline. Indeed, we could feel the temperature change when we dove off the deck and descended more than a few meters deep below the surface! We took advantage of these calm conditions to do a Secchi disk measurement and recorded a whopping 26.2 m depth in the clear water!

Biscay Bay Temperature PlotWhen the wind picked up from the North that evening, we were able to hoist the sails and start the fast downwind run to the corner of Spain and around Cape Finnisterre.  As we sailed through the southern part of the Biscay Bay, we crossed several ocean fronts that had clear lines of different currents and waves.  The frontal zones were as long as the eye could see, several hundred meters wide, and semi-periodic with a wave length of approximately 10 km.  Perhaps these were internal waves reaching the surface that were enabled by the strong and shallow thermocline from the calm, warm period?

As we rounded the northern tip of Spain and sailed towards Vigo, the seawater temperature (and air temperature!) dropped substantially.  This is the classic coastal upwelling case where the strong Northerly winds force the surface water to the right  (offshore) and the water near the coast is replaced by cold, nutrient rich deep water.  This is where the fishing is exceptional, and we dodged fishing boats for the next 50 miles until we reached the protected Ria of Vigo.

Secchi Deploy

Preparing to lower the RBR CTD in the warm, blue waters of Biscay Bay.

Secchi Lower

Taking a Secchi disk reading (26.2 m!) in Biscay Bay.

Citizen Oceanographers

The crew of Laridae are very excited to be part of the Indigo V Expeditions Citizen Oceanographer research program.  The Indigo V Expedition program was founded by oceanographers and sailors in an attempt to collect high-quality oceanographic data on water quality and microbial life from very remote places in the oceans.  Large oceanographic research vessels are very expensive to bring to all corners of the oceans, so the team at Indigo V have found a way to outfit voyaging sailors with high-quality scientific tools.  The sailors collect data while they are roaming the oceans for a small fraction of the cost of running a large research vessel.  The research team at Indigo V Expeditions have been making important scientific discoveries and getting recognized widely in the scientific community.  They have published a paper on the Citizen Oceanography concept and presented at the White House!

The Siegel crew on Laridae were recently interviewed to become one of the official Citizen Oceanographer Explorers with the Indigo V team.  We look forward to working more closely with them soon!



The origins of Citizen Oceanography. (Credit: Indigo V Expeditions)


The Marine Microbiome – tiny, marine micro-planktons are the most abundant organisms in the ocean, yet they are the most understudied.  (Credit: Indigo V Expeditions)

IndigoV YouTube