Science operations end as NOAA Ship Okeanos Explorer comes into port. Manta net operations to sample for plastics were completed last night for a total of 40 manta net tows conducted at 28 stations over the course of 10 days. The Continuous Plankton Recorder was pulled out of the water early this morning after sampling plankton over more than 1,950 nautical miles on this cruise. The EM302 multibeam sonar was turned off this morning and by early afternoon Okeanos Explorer crossed underneath the Golden Gate Bridge and docked in San Francisco Harbor, bringing the EX1006 “Always Exploring” cruise to an end.
On board personnel are busy making preparations to come into port, and shortly afterwards, winter dry dock. Operations continue to run smoothly as the ship's crew conducts routine training and maintenance. The last manta net tow of the cruise was conducted this evening. Today's manta net results suggest Okeanos Explorer has left the Pacific "Garbage Patch". The ship completed its last of 3 time changes today, bringing it up-to-speed with the West Coast. We expect to arrive in San Francisco tomorrow morning.
Manta Net operations continue to run smoothly as Okeanos Explorer remains underway towards San Francisco. Tows are conducted four times a day, and have consistently collected a variety of marine life along with bits of plastic. Some samples have contained a relatively high abundance of plastic, whereas other samples hosted a relatively low abundance (perhaps due to high winds and surface mixing). Since Okeanos’ apparent entrance to the “Garbage Patch” on October 21st, manta net tows have collected plastic every day.
Continued from Okeanos Explorer's previous cruise from Guam to Hawaii, an instrument called a Continuous Plankton Recorder (CPR) is being towed about 10m deep behind the ship as she makes her way to San Francisco. As the CPR is towed, seawater enters the instrument and is filtered through a slowly advancing strip of silk mesh, sampling plankton. Today, the CPR reached the end of her second strip of silk mesh, and with it the successful sampling of 1,030 nautical miles of ocean. By the time Okeanos Explorer arrives in San Francisco, nearly 1,900 nautical miles of ocean will have been sampled during this cruise. Combined with the previous cruise, the data will provide a picture of plankton diversity across more than 5,100 nautical miles of the Pacific Ocean.
Late last night, the EM302 multibeam sonar on Okeanos Explorer acquired data overtop of two seamounts that previous satellite altimetry data revealed only as relatively small mounds on the seafloor, rising at most a few hundred meters. The ship’s multibeam data, however, revealed these seamounts to be greater than 1000 meters tall. Neither of these features is listed on the available NOAA chart for the area. With the data available onboard the ship, these two seamounts are being marked as two “potential discoveries” and require further detailed research before conclusive statements can be made. This is a common situation aboard Okeanos Explorer – although much data is collected, conclusively determining whether something is “new” or a “discovery” is rarely immediate. Sometimes potential new features such as these seamounts are recognized by scientists or technicians participating in the exploration, whereas other times new or unique findings come later, after the data has been sent to shore and made available for others to comb through to make or catalyze discoveries.
While Okeanos Explorer continues underway to California, onboard science operations become smoother and more efficient. Mapping operations continue to go well as watchstanders acquire and process data around-the-clock. Water depths during this cruise have consistently reached depths greater than 5000m, approaching the maximum limits of the EM302 multibeam sonar’s capability to resolve small-scale features. Satellite-derived bathymetry (Sandwell & Smith) provides invaluable guidance on what the mapping team onboard the Okeanos Explorer will encounter while exploring new areas of the seafloor. Sometimes, however, the satellite-derived bathymetry is misleading - in today’s case (see associated image), we were expecting to see a slight rise in the seafloor, indicated by the red oval feature in the background image. In reality, a series of small ridges of up to 125 meters high, indicated by black arrows, was found.
Today’s Manta Net samples suggest that NOAA Ship Okeanos Explorer has entered an area referred to as the “Pacific Garbage Patch.” Four Manta Net tows are conducted each day onboard the Okeanos Explorer cruise from Hawaii to San Francisco Bay to sample for plastics. The afternoon and evening samples all revealed relatively large quantities of plastic. Most of the plastic in the “Garbage Patch.” is relatively small – invisible to satellites, and difficult to see with the naked eye. Although watch standers spent hours watching the sea surface today, few items indicated the ship might be in the “Garbage Patch.” Its presence was not apparent until today’s Manta Net samples were brought on board, concentrating debris located in an area the size of an olympic swimming pool into a pint-size container. Large and small bits of plastic filled the container, interspersed with a variety of marine-life. All onboard are curious to see what the days ahead may bring.
While everyone onboard settles into Okeanos Explorer’s ship-board routine, the sea-state slowly picks up as the ship heads northeast towards a swell. Science operations continue with daily Manta Net deployments, and towing of the Continuous Plankton Recorder. Multibeam data acquisition continues, revealing previously unknown seafloor features in greater detail.
NOAA Ship Okeanos Explorer departed Pearl Harbor, HI this morning and began her transit to California for the winter inport. Once outside of Pearl Harbor, the EM302 multibeam sonar was turned on and data acquisition commenced. Science operations started soon after with deployment of the Continuous Plankton Recorder for its first calibration tow, and the first Manta Net deployment in the evening. Safety drills were conducted in the afternoon and new personnel continue to get familiar with shipboard operations.