Meredith Salmon: CTDs and Cribbage! July 24, 2018

NOAA Teacher at Sea

Meredith Salmon

Aboard NOAA Ship Okeanos Explorer

July 12 – 31, 2018


Mission: Mapping Deep-Water Areas Southeast of Bermuda in Support of the Galway Statement on Atlantic Ocean Cooperation

Weather Data from the Okeanos Explorer Bridge

Latitude: 28.34°N

Longitude: 64.14°W

Air Temperature: 28.16°C

Wind Speed:  17.34 knots

Conditions: partly sunny  

Depth: 5060.32 meters

Science and Technology Log

Understanding the physical properties of seawater such as temperature, salinity, and depth are important parameters for studying ocean processes. Fortunately, A CTD is an acronym for an electronic instrument that is used on research vessels to measure three important factors: conductivity, temperature, and depth. These data points are key exploration components used aboard the Okeanos Explorer.


Conductivity is a measure of how well a solution conducts electricity and it is directly related to salinity. When salinity measurements are combined with temperature readings, seawater density can be determined. This is crucial information since seawater density is a driving force for major ocean currents.


The CTD itself is housed in a steel container and is surrounded by a ring of plastic bottles. These water sampling bottles can be individually triggered at various depths to collect water samples allowing scientists to analyze water at specific depths at a particular place and time. The entire structure is connected to a rosette that is lowered by a hydrographic winch crane, and this rosette is capable of making vertical profiles to depths up to 6,800 meters.  

ctd 3
CTD unit aboard the Okeanos Explorer


Features in the deep ocean such as hydrothermal vents and underwater volcanoes are associated with changes in chemical properties of seawater, so CTDs are used to measure chemical and physical properties associated with these structures. For instance, changes in water temperature may indicate the presence of hydrothermal vents or volcanoes. Since these features are located in deep waters, a CTD will be raised and lowered throughout the water column as the ship moves over the survey area. Although a CTD cast has not been completed on our expedition, these procedures require effective communication between scientists in the lab and the hydrographic crane operator. Scientists in the lab can monitor the CTD measurements in real time in the lab, and communicate depth for water capture in the rosette bottles to the crane operator. Once back on board, scientists can retrieve the water samples from the bottles and take them into the lab for further analysis.

CTD rosette complete with water sampling containers

Personal Log

We have continued to map the survey area, load XBTs, and take sunphotometer readings throughout the course of the week. Since they are few and far between, everyone looks forward to turns. The entire turning process requires effective communication with the bridge and survey team and can take approximately 15 to 20 minutes to complete.

A turn pictured in the Seafloor Information System (SIS) program

Aside from waiting for turns, we have been playing daily trivia or bingo as well as card games including cribbage! Since the cribbage tournament is underway, we have been practicing, playing, and watching other games. There have been some serious upsets and victories so the finals are going to be interesting for sure.

Okeanos Cribbage Tournament Bracket
Okeanos Cribbage Tournament Bracket
cribbage tournament
Savannah vs. Charlie!
cribbage 6
Fernando vs. Christian!

We learned that we are heading back to Norfolk for dry dock towards the end of July so we will need to stop surveying soon to transit back to Virginia. It is crazy to think that we only have a couple more days at sea!

double rainbow.jpeg
A double rainbow seen from the boat deck!


Double Rainbow
Savannah, Sally, and I enjoying the view!

Did You Know?

Some CTD instruments are so fast that they measure the conductivity, temperature, and depth 24 times each second! This provides a very detailed description of the water being tested.


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