Caroline Singler, August 13-15 2010

NOAA Teacher at Sea: Caroline Singler
Ship: USCGS Healy 

Mission: Extended Continental Shelf Survey
Geographical area of cruise: Arctic Ocean north of Alaska in the Canada Basin
Date of Post: 16 August 2010

Follow the Leader – 13 – 15 August 2010

Location and Weather Data from the Bridge
Date: 13 August 2010 Time of Day: 2100 (9:00 p.m.) local time; 04:00 UTC
Latitude: 73º0’N

Longitude: 145º3’W
Ship Speed: 3.9 knots
Heading: 1.8º (north)
Air Temperature: 2.0ºC/35ºF
Barometric Pressure: 1018.9 millibars (mb) Humidity: 100%
Winds: 3-5 Knots SW
Sea Temperature: -0.4ºC Salinity: 25.37 PSU
Water Depth:~3600 m

Ice with Ridges
Ice with Ridges

Date: 14 August 2010

Time of Day: 2105 (9:05 p.m.)
local time; 04:05 UTC
Latitude: 73º36.4’N Longitude: 146º19.21’W
Ship Speed: 4.7 knots Heading: 223º (southwest)
Air Temperature: 2.15ºC/35.88ºF
Barometric Pressure: 1022.3 mb Humidity: 92.1%
Winds: 12.2 knots SE Wind Chill: -3.1ºC/26.5ºF
Sea Temperature: -0.7 ºC Salinity: 24.84 PSU
Water Depth: 3708.6 m
Open Water and Beautiful Sky
Open Water and Beautiful Sky
Date: 15 August 2010
Time of Day: 1500 (3:00 p.m.)
local time; 22:00 UTC
Latitude: 72º56.4’N
Longitude: 150º9.0’W
Ship speed: 11.8 knots
Heading: 220º (southwest)
Air Temperature: 5.6ºC/42.2ºF
Barometric Pressure: 1015.6 mb
Humidity: 98.1%
Winds: 17.7 knots E
Wind Chill: 1.7ºC/35.1ºF
Sea Temperature: 3.9ºC
Salinity: 24.5 PSU
Water Depth:3691.1 mScience and Technology Log

The Extended Continental Shelf Project is a multi-year effort between the United States and Canada. The two countries share knowledge, resources, and information to allow greater coverage of the region and more cost effective achievement of the mission objectives. For this mission, the USCGC Healy is working in tandem with the Canadian Coast Guard ice breaker Louis S. St. Laurent, called Louis(pronounced “Louie”) for short. Healy is responsible for collecting bathymetric data and shallow subsurface imaging while Louis performs deeper subsurface imaging with her air-gun array. The instrumentation on Louis is towed behind the ship and requires a clear path through the ice; therefore, Healy’s primary responsibility when the ships are in ice is to lead and break ice for Louis. Healy opens a path and Louis follows, typically about one to two miles behind depending on ice and visibility conditions. It was foggy for most of the day on Friday as we led the way north along the first track line. The only way I knew that Louis was behind us was by watching the ship tracking chart and listening to occasional radio chatter between the two boats as the crews communicated about ice conditions. Skies cleared as we moved farther north and deeper into the ice on Saturday. Near midday, the fog lifted and there was Louis, first emerging like a ghostly image out of the fog and then, as we made the turn onto a new transect line, she was in full view. By Sunday afternoon we were heading south in open water, so Healy moved away fromLouis to conduct other business while our ice breaking services were not needed.
USCGS Healy Leading USCGS Lewis
USCGC Healy Leading CCGS Louis
USCGS Louis on Ice
CCGS Louis on Ice
While multibeam sonar allows us to “see the bottom”, subbottom profiling uses a different sound-producing system to see what is under the bottom. Geologists use the subbottom data both from Healy andLouis to estimate sediment thickness and make inferences about sediment types and structures beneath the seafloor. It makes me think of Superman’s x-ray vision! Like multibeam sonar, subbottom profilers are echosounding devices. They are active sonar systems – sound signals are transmitted and received by the instrument.
Healy’s profiler is a “chirp” system mounted inside the bottom of the ship’s hull – so called because it sounds like a bird chirping, a sound that one hears in the background throughout the ship. It releases high frequency pulses of acoustic energy that travel through the water column and (in theory) hit the seafloor and penetrate into subsurface materials to depths of tens of meters. Signals are reflected at the seafloor and at interfaces between different subsurface layers within the seafloor. The reflection of acoustic energy depends on the “acoustic impedance” of the material encountered. Acoustic impedance is related to the density of the material and the velocity of sound in that medium. Different materials have different acoustic impedance and therefore different reflectivity. The concept is similar to that of albedo when one considers the reflection of solar energy from different surfaces. A smooth, light-colored surface like a field of snow reflects a high percentage of incoming solar rays and therefore has a high albedo– hence the glare that hurts your eyes on a sunny day. Dark-colored surfaces reflect much lower percentages of incident light and therefore have low albedo. (They also absorb more energy which is why they get hotter on a sunny day.)
With subbottom profiling, sands typically reflect sound differently than mud, and layers or other structures in the subsurface result in different signal strengths returning to the receivers on the ship. The picture on the right shows an image of the raw chirp data displayed on the computer screen at the watch stander station. It does not show a lot in this state, but after processing the data will provide important information about the subsurface in the Arctic Ocean.
Chirp Display
Chirp Display

Subbottom surveying on Louis is performed with a multi-channel air gun system that is towed behind the ship. Three air guns, powered by air compressors on the ship’s deck, provide the acoustic energy source. A streamer with an array of 16 hydrophones trails behind the air guns; the hydrophones receive the return signals reflected by the seafloor and subsurface sediments. In open water, the air guns are attached to a float and hang about three to five meters below the surface, at a distance of about 100 meters behind the ship. In ice, the air guns are attached to a metal sled (depressor) that hangs below the sea surface (and hence the ice) to a depth of about 10 meters and at a distance of about 10 meters behind the ship. When fired, the air guns simultaneously emit large air bubbles into the water column. As the bubbles collapse, an acoustic pulse is produced that moves through the water. It is similar to what happens in the atmosphere when air rapidly expands and contracts as a lightning bolt passes through, creating the sound we know as thunder. The air guns generate sound at a lower frequency than the chirp system; sound at these lower frequencies penetrates deeper into the subsurface but produces lower resolution than the higher frequency chirp system. Such air gun systems can provide images to depths of several kilometers below the seafloor.

WHOI Subbottom Profiling Diagram
WHOI Subbottom Profiling Diagram

Image source: USGS Woods Hole Science CenterReferences:
USGS Woods Hole Science Center
NOAA Coastal Services Center

Personal Log
Saturdays are “Field Days” on Healy. No, we did not all get into boats and take a trip away from the ship or get out onto the ice. Field Day is a fancy way of saying that it is time for cleanup and inspection of common areas and personal berthing areas. All personnel on board are responsible for trash removal and cleaning of staterooms, restrooms and common living and working spaces. Anyone who is not on duty pitches in to clean the Science lounge and labs – vacuuming, sweeping, washing floors and generally putting things in order. The “trash vans” are open twice a week; everyone brings trash and recycling to two large blue bins on the port side of the 02 deck (the same deck as the science staterooms). Coast Guard volunteers work the trash vans. Healy will be at sea for another long mission after this one, so efficient trash removal and storage is critical. Healy personnel are dedicated to recycling and have an award winning recycling program on board – no small feat when it is necessary to haul it all around for months at sea. Think about that when you are tempted to complain about separating recyclables from trash at home or at school.

Since everything was neat and tidy, I decided it was a good time to show you my living space on Healy. Science staterooms are set up for three occupants, but on this trip we have two people per room. I share a room with Sarah Ashworth, a marine mammal observer; she is currently on Louis, so for now I have my own room. The room is more spacious than I expected on a ship, similar in size to a lot of college dorm rooms.

My Rack
My Rack

Space is used very efficiently. There are bunk beds; Sarah has more experience at sea than I, so she has the top bunk or “rack”.

Each person has a good sized locker for clothes and since there are only two of us, we each have a desk and filing cabinet, so there is plenty of storage space – more than we need for our personal belongings.
Sink and Locker
Sink and Locker
Desk Area
Desk Area

There’s nothing like a room with a view, even if they left the tape on the window the last time they painted the ship.

Sun on Water Through Porthole
Sun on Water Through Porthole

Each room has its own sink, and shares a bathroom with the adjoining room. Okay, they call it a “head” on a ship; don’t ask me why! The bathroom is small, but one does not linger when taking a “sea shower”, and there is always plenty of hot water. In case you ever wondered what a marine toilet looked like, here it is.

Marine Toilet
Marine Toilet

We headed towards Barrow on Sunday to pick up a crew member and some supplies for the Louis. There was a steady wind from the east for most of the afternoon, and the boat was rolling a little, but I was more prepared for it this time than I was the first time it happened, but I still stumble when I walk down the hall.

We have had beautiful views of ice, sea, and sky for the last few days.

Ice with cool clouds
Ice with cool clouds
Waves and sky
Waves and sky

Debra Brice, November 22, 2003

NOAA Teacher at Sea
Debra Brice
Onboard R/V Roger Revelle
November 11-25, 2003

Mission: Ocean Observation
Geographical Area: Chilean Coast
Date: November 22, 2003

Data from the Bridge
1.  221600Z Nov 03
2.  Position: LAT: 20-00.0’S, LONG: 083-44.8’W
3.  Course: 090-T
4.  Speed: 12.6 Kts
5.  Distance: 102.7 NM
6.  Steaming Time:  8H 06M
7.  Station Time:  15H 54M
8.  Fuel: 2583 GAL
9.  Sky: OvrCst
10. Wind: 140-T, 14 Kts
11. Sea: 140-T, 2-3 Ft
12. Swell: 130-T, 3-4 Ft
13. Barometer: 1015.9 mb
14. Temperature: Air: 20.0 C, Sea 19.4 C
15. Equipment Status: NORMAL
16. Comments: Deployment of surface drifter array #4 in progress.

Science and Technology Log

NOAA Climate Studies of Stratocumulus Clouds and the Air-Sea Interaction in Subtropical Cloud Belts. Today we are still underway and I am going to talk about another science group that is onboard and how their research is related to the Stratus Project. We are presently located along the coast of Northern Chile and I just finished interviewing scientist Chris Fairall with NOAA’s Environmental Technology Laboratory in Boulder, Colorado.  A group of 4 ETL scientists are participating in a study of oceanography and meteorology in a region of the ocean that is known for its persistent stratus clouds.

The Woods Hole Oceanographic Institution (WHOI) has maintained a climate monitoring buoy at this location for the last 3 years.  Each year they come out to take out the old buoy and replace it with a brand new one with fresh batteries and new sensors.  A year in the marine environment takes a toll on the toughest instruments.  This is a special buoy which is festooned with atmospheric sensors to measure air-sea fluxes and with a long chain of subsurface instruments to measure ocean currents, temperature and salinity.  If you go to the WHOI website ( you can read about this project and see the data from the buoy.  The data are transmitted via satellite everyday.  WHOI removed the old buoy on Nov 17 and put in a new one on Nov 19.

Why are these clouds so important?  Because the earth’s climate is driven by energy from the sun and clouds dominate how much solar energy reaches the surface.  On average, almost 40% of the sun’s energy is reflected back into space and half of that is reflected by clouds.  In the cloudy regions more than 60% of the sun’s energy can be reflected by clouds.  The surface temperature of the ocean is a result in a near balance between solar heating and cooling by evaporation and cooling by infrared (IR) radiation from the water surface into the sky.  The global circulation of the atmosphere and ocean are driven by region differences in this net heat input, so clouds have a direct effect on the winds and currents. Cloud effects on the ocean surface energy balance are very tricky because clouds affect both the solar flux (i.e., by reflecting energy back into space) and the IR flux.  It might surprise you, but the sky is ‘warmer’ when there are low clouds present than when the sky is clear.  Think about those cold clear nights in the winter and note the ‘cold’ often appears with ‘clear’. More specifically, the IR radiation coming down from the sky is higher when clouds are present than when skies are clear.  In the tropics and sub-tropics, the solar reflection cooling effect of the clouds is much stronger than their compensating IR warming effect.  Thus, these stratus clouds play an important role in keeping the subtropical oceans cool.

The region we are studying is one of 5 stratus regions around the globe (west coast of U.S.. west coast of S. America, west coast of S. Africa, west coast of N. Africa/Europe, and the west coast of Australia) that occupy vast expanses of ocean.  Both of the pictures I attached to this log show the stratocumulus clouds in this region.  Each of these cloud types has about the same area-average liquid water content but, because of the horizontal distribution, vastly different radiative properties.  The physical processes that lead to these different forms are one of the objective of the ETL studies.

Clouds are formed through various related mechanisms; most involve cooling air to below its dew point temperature so droplets condense ( i.e., clouds are suspensions of liquid water drops with typical sizes of about 10 micrometers radius).  Convective clouds are associated with cooling in strong updrafts; fog and many mid-atmospheric clouds form when an atmospheric layer cools by IR radiation.  The stratus clouds we are studying are quite different.  The key elements are a strong atmospheric cap that traps ocean moisture in a fairly thin ( about 1 km high) boundary layer over the surface.  The stratus clouds occupy the top of the trapped layer from just below the cap to down the altitude ( cloud base height) where temperature and dew point just meet.  Below that, the relative humidity is less than 100%.  The ‘cap’ on the atmosphere boundary layer is warm/dry air descending in subtropical regions, particularly on the western boundaries of continents.  This descending air is actually driven by deep convection in the tropics.  To meteo- nerds this is an amusing paradox – cool stratus clouds off Chile and California are essentially caused by thunderstorms near the Equator.

Clouds are a pain to study because they are so inaccessible.  To get into clouds with sensors you need a really tall tower, a tall building or an aircraft.  Most of these are hard to come by 500 miles from land. Thus, most climate studies of clouds rely on remote sensing methods using satellites and surface based sensors.

ETL has deployed a suite of remote sensors on the R/V Revelle to study clouds from the bottom. The showcase sensors are a special high frequency cloud radar and a 2-frequency microwave radiometer system (this system is the attached picture of the large, white van).  This is the 6th time such sensors have ever been deployed from ships and only the second time to a stratocumulus region.  The first time was to this same spot in 2001; see the web site: for information on that cruise.

The radar has a wavelength of 8mm, which is so small that it is sensitive enough to receive  detectable signals from scattering cloud droplets.  With this device the ETL group can determine profiles of cloud properties ( such as size of the droplets) through the entire cloud.  The microwave radiometer uses the emissions from the atmosphere at 2 frequencies ( 21 and 31 GHz, or wavelengths of 14 and 9mm) to determine cloud base height and, most importantly, we also measure IR and solar radiative energy reaching the surface.  Instead of just looking at the cloud, they collect megabytes of data every minute.  The beauty of this set up is that they can simultaneously measure the effect the clouds have on the surface energy budget of the ocean and the cloud properties ( liquid water content, thickness, soiled versus broken, number of cloud droplets per unit volume) that go with the radiative effects.  The ETL group are only out here a few weeks each year, but their detailed measurements provide vital information to interpret long-term continuous time series measured by the buoy or inferred from satellite overpasses.

Personal Log

We are surveying for a location for the PMEL Tsunami buoy and the weather is beautiful.  Due to our heading we have lost internet connections periodically.  The food on the REVELLE  is really amazing; last night we had steak and King crab for dinner and a group of the crew and science party met in the lounge to watch a movie.  Card games and cribbage are popular in the dining room and some of us just sit outside and enjoy the sunsets.  I’m going to sleep early as I have the late watch.