Underway Salinity/Temperature and Moored Temperature

Sterling A. Wheaten

http://uncw.edu/cmsr/FacilitiesRVcapefear.htm

Background: Measurement StationsIn both cruises we made various measurements along the Lower Cape

Fear estuary at M18, M23, M35, M42, M54, M61, and HB.

http://uncw.edu/cmsr/aquaticecology/laboratory/LCFRP/index.htm

Background: Continuous Measurements

Temperature and Salinity were measured every 5 seconds during both cruises

using a Sea-Bird 21 thermosalinograph.

http://www.seabird.com/pdf_documents/manuals/21_025.pdf

Background: Thermosalinograph PlotsTSG plot: September 14, 2009

Cruise 1 TSG plot of Lower Cape Fear Estuary.Septmeber 14, 2009

Y axis: time (in seconds)X axis: Salinity and Temp (0C)

Green line isTemperature

Blue line is Salinity

Important Concepts: Positioning of Stations

Station Miles InlandM18 0M23 3.54M35 9.89M42 13.79M54 17.24M61 21.02HB 24.54

Carroll CTD Presentation. 2008

Heading up river, salinity decreases

Surface temperature stays relatively constant

Important Concepts: Positioning of Stations

http://uncw.edu/cmsr/aquaticecology/laboratory/LCFRP/index.htm

Salinity vs. Time, M18 to HB

Data Obtained: Cruise 1

Salinity

Time (seconds)

Data Obtained: Cruise 1

Data on graph where salinity remained constant implies a stop at a station.

This is verified upon comparison to the CTD data, as seen in the next slide.

Underway M18 to HB with CTD data

Data Obtained: Cruise 1

M18: 30.5

M23: 28.08

M35: 20.05

M42: 17.26M54: 15.53

M61: 12.72

HB: 6.04

Salinity

Time (seconds)

Salinity vs. Time, M18 to HB

Data Obtained: Cruise 2

Salinity

Time (seconds)

Underway M18 to HB with CTD data

Data Obtained: Cruise 2

M18: 29.12 M23: 26.5

M35: 23.06

M42: 17.45 M54: 15.29

M61: 13.45

HB: 5.98

1. Shorter time to take measurements resulted in the vessel not being as stationary.2. This data does not correlate as well with the CTD data.

Data Obtained: Cruise 1 vs. Cruise 2S

alin

ity

Miles Inland

Data Obtained: Cruise 1 vs. Cruise 2

• In comparison, Cruise 2 had a lower salinity initially at M18.

• Station stops during Cruise 2 were much shorter, resulting in

less distinction between stations.

• Cruise 1 had a significant decrease in salinity from M23 to

M34 as compared to Cruise 2.

Moored Temperature Device at HBA temperature data logger was left at M35 and HB on September

14, 2009 and collected October 26, 2009 (6 weeks)

• The data logger left at M35 was swept away and could not be found upon

collection

The instrument used was a TidBit v2 Data Logger• precision sensor for ±0.2 °C accuracy • Waterproof to 300m• Set to record temp. every 15 minutes

http://onsetcomp.com/products/data-loggers/utbi-001

Moored Temperature Device at HB

At left, Dr. Bingham and Sterling prepare the TidBit v2 for mooring and at right, leaving the anchored data logger with buoy attached at station M35. September 14, 2009

Moored Temperature Device at HB

Above, from clockwise, finding, collecting, and observing the moored TidBit v2 at station HB. October 16, 2009

Moored Temperature Device at HBT

empe

ratu

re,

°C

Data obtained by TidBit v2 at station HB

14 16 18 20 22 24 26 28 30 2 4 6 8 10 12 14 16 18 20 22 24

September October

15

17

19

21

23

25

27

29

Moored Temperature Device at HB

There is a large minimum in the temperature around October 20

The decreasing trend in the temperature as time increased was due to seasonal change.

The data points oscillate, which are representative of the semidiurnal tide.

Data Interpretation

Moored Temperature Device: 48 hour periodT

em

per

atu

re, o

C

The oscillations in the data are from the semidiurnal tide.

Below shows data obtained from September 17-18, 2009.

25

25.2

25.4

25.6

25.8

26

0 6 12 18 24 30 36 42 4812 6 12 6 12 6 12 6 12

September 17 September 18

am pm pmam

Conclusions:

TSG data from both trips showed a decrease in salinity as we headed up river and minimal surface temperature changes.

The data from the moored temperature device showed oscillations due to the semidiurnal tide and over the 6 weeks, the temperature followed a decreasing trend due to seasonal change.