Measurements within OTC

The marine network consist of a variety of ships and fixed station installations covering the open ocean and coastal areas, and for this purpose the network is divided into 4 categories; Voluntary Observing Ships (VOS), Repeat Ocean Sections (ROS), Fixed Ocean Stations (FOS), and Marine Flux Towers (MFT). For each category the required parameters (called core parameters) and the frequency of measurements are defined in the table below. The table also defines the criteria to become a Class 1 and Class 2 station. This classification is a part of the ICOS station labelling process.

 

Platform type

Type

Parameters

Frequency

(open/coastal)

Criteria - Class 1

Criteria - Class 2

VOS

Core Sea surface fCO2  Quasi-continuous1 ± 2 matm ± 5 matm (for flow-through equilibrator- based systems)
± 10 matm (for other systems)
Core Intake temperature Continuous ± 0.05 °C ± 0.05 °C
Core Water vapour pressure2 Continuous ± 0.5 hPa ± 0.5 hPa
Core Equilibrator pressure3 Continuous ± 2.0 hPa ± 2.0 hPa
Core Equilibrator temperature3 Continuous ± 0.05 °C ± 0.05 °C
Core Delta-T4 (difference between intake and equilibrator temperature or sensor Continuous < 1.5 °C
< 3 °C
< 1.5 °C
< 3 °C
Desirable Sea surface salinity Continuous ± 0.02  ± 0.02 
Desirable Atmospheric xCO2 Quasi-continuous ± 1 matm ± 5 matm
Desirable Dissolved oxygen Continuous ± 1% ± 1%
Desirable Atmospheric flask samples for CO2, CH4, N2O Discrete As determined by the ICOS FCL As determined by the ICOS FCL
Desirable Chlorophyll-fluorescence Continuous 2 % 2 %
Desirable Wind speed/Air temp/Sea level pressure Continuous or discrete    
Desirable Dissolved inorganic nutrients5 Discrete ± 1% ± 1%
Desirable pH Continuous ± 0.01  ±  0.01 
Desirable DIC Discrete ± 1.5 mmol kg-1 ± 4 mmol kg-1
Desirable TA Discrete ± 3 mmol kg-1 ± 6 mmol kg-1
Desirable δ 13C Discrete ±  0.1‰ ±  0.1‰
Desirable CH4 Discrete/continuous ±  1% of atm. saturation ±  1% of atm. saturation
Desirable N2O Discrete/continuous ±  1% of atm. saturation ± 1% of atm. saturation

ROS

Core

Two out of four:

DIC

TA

pCO2

pH 

> 1 decade-1

 
± 1.5 (< 4) mmol kg-1

± 3 (< 6) mmol kg-1 

± 1 (<3) matm 

± 0.005 (<0.005) 

 
± 1.5 (4-25) mmol kg-1

± 3 (6-30) mmol kg-1

± 1 (3-5) matm

± 0.005 (0.005-0.01)

Core Sea temperature > 1 decade-1 ± 0.002 °C ±0.002 °C
Core Sea salinity > 1 decade-1 ± 0.003 (<0.005)  ± 0.003 (0.003-0.02) 
Core Dissolved inorganic nutrients8 > 1 decade-1 ± 1 (<2)% ± 1 (2-5)%
Core CFC-11/ CFC-12 > 1 decade-1 ± 1 (<5)% ± 1 (5-20)%
Core SF6 > 1 decade-1 ± 1.5 (<5)% ± 1.5 (5-20)%
Desirable

Dissolved oxygen

Winkler

CTD sensor

> 1 decade-1

 

± 0.5 (<1)%

± 1% 

 

± 0.5 (1-5)%

± 1%

Desirable CH4 > 1 decade-1 ± 1% of atm. saturation ± 1% of atm. saturation
Desirable N2O > 1 decade-1 ± 1% of atm. saturation ± 1% of atm. saturation
Desirable δ 13C > 1 decade-1 ± 0.04‰ ± 0.04‰
Desirable D 14C > 1 decade-1 ± 5‰ ± 5‰

FOS

discrete

Core

Two out of four:

DIC 

TA

pCO2

pH

> 1 yr-1/monthly

 

± 1.5 / ± 1.5 mmol kg-1

± 3 / ± 3 mmol kg-1 

± 1 / ± 1matm 

± 0.005 / ± 0.005

 

± 4 / ± 4 mmol kg-1

± 6 / ± 6 mmol kg-1 

± 3 /± 3matm 

± 0.01 / ± 0.01 

Core Sea temperature > 1 yr-1/monthly ± 0.02 / ± 0.02 °C ± 0.02/ ± 0.02 °C
Core Sea salinity > 1 yr-1/monthly ± 0.03/ ± 0.03  ± 0.03 / ± 0.03 
Core Dissolved inorganic nutrients10 > 1 yr-1/monthly ± 1 / ± 1% ± 1 / ± 1%
Desirable Dissolved oxygen > 1 yr-1/monthly ± 1 / ± 1% ± 1 / ± 1%
Desirable CH4 > 1 yr-1/monthly ± 1 / ± 1% of atm. saturation ± 1 / ± 1% of atm. saturation
Desirable N2O > 1 yr-1/monthly ± 1 / ± 1% of atm. saturation ± 1 / ± 1% of atm. saturation
Desirable δ 13C > 1 yr-1/monthly ± 0.04 / ± 0.04‰ ± 0.04 / ± 0.04‰
Desirable D14C > 1 yr-1/monthly ±  5‰ ±  5‰
Desirable CDOM (~300 nm) - /monthly ± 0.01 m-1 ± 0.01 m-1
Desirable Chlorophyll - /monthly    
Desirable DOC - /monthly    

FOS

(quasi-) continous

Core pCO2 > 1 day-1/ > 3 day-1 ± 5 / ± 5 matm < 10 / < 10 matm
Core Sea temperature > 1 day-1/ > 3 day-1 ± 0.02 /± 0.02 °C ± 0.02 /± 0.02 °C
Core Sea salinity > 1 day-1/ > 3 day-1 ± 0.03 / ± 0.03  ± 0.03 / ± 0.03 
Core Dissolved oxygen11 > 1 day-1/ > 3 day-1 ± 1 / ± 1% ± 1 / ± 1%
Desirable pH > 1 day-1/ > 3 day-1 ± 0.01 / ± 0.01  ± 0.01 / ± 0.01 
Desirable Dissolved inorganic nutrients12 > 1 day-1/ > 3 day-1 ± 1 / ± 1% ± 1 / ± 1%
Desirable Atmospheric pCO2 > 1 day-1/ > 3 day-1 ± 1 matm  
Desirable Wind speed/Air temp/Atm pressure Continuously/ continuously    
Desirable CH4 > 1 day-1/ > 3 day-1 ± 1 / ± 1% of atm. saturation ± 1 / ± 1% of atm. saturation
Desirable N2O > 1 day-1/ > 3 day-1 ± 1 / ± 1% of atm. saturation ± 1 / ± 1% of atm. saturation
Desirable Chlorophyll > 1 day-1/ > 3 day-1    
Desirable CDOM  - / > 3 day-1 ± 0.01 m-1 ± 0.01 m-1
Desirable Irradiance  - / > 3 day-1    
Desirable PAR  - / > 3 day-1    
MFT Core Atmospheric CO2 1h ± 0.5%  ± 1.5% 
Core  CO2 flux  1h ± 2% ± 5%
Core  Atmospheric pressure  1h ± 0.1%  ± 0.1% 
Core  Wind speed 1h ± 0.3 m/s ± 0.5 m/s
Core  Wind direction 1h ± 3 ° ± 6 °
Core  Atmospheric temperature  1h ± 0.2 °
ventilated
± 0.2 °
ventilated
Core  Atmospheric humidity 1h ± 1%  ± 1% 
Core Sensible heat flux 1h ± 10% ± 10%
Core H2O flux 1h ± 2% desirable
Core Friction velocity 1h ± 2% ± 2%
Core Sea surface pCO2 > 3 day-1  ± 5 matm < 10 matm
Core Sea temperature > 3 day-1 ± 0.02 °C ± 0.02 °C
Core Sea salinity > 3 day-1 ± 0.03  ± 0.03 
Desirable SW_in, LW_in  1h    
Desirable PAR/PPFD 1h    
Desirable Precipitation  1h WMO guidelines  WMO guidelines 

 

1No Carbon-VOS measuring system can truly be continuous, as regular gas standards need to be measured; hence the term quasi-continuous is used here for atmospheric and sea surface fCO2.
2If the headspace gas analysed is not dried completely prior to measurement.
3If a continuous flow-through equilibrator system is used.
4Delta-T criteria are < 1 °C for measurements at low and mid- latitudes; when a Carbon-VOS is close to the ice-edge, this is relaxed to < 3 °C.
5Dissolved inorganic nutrients=NO3, PO4, SiO2.
6The two numbers refers to within cruise precision and, in parenthesis, between cruises bias. The numbers within parenthesis are the maximum acceptable bias following the 2nd level QC in GLODAP.
7The two numbers refer to within cruise precision and, in parenthesis, between cruises bias. The numbers within parenthesis are the range where the 2nd level QC in GLODAP recommends adjustments. 
8Dissolved inorganic nutrients=NO3, PO4, SiO2.
9The numbers refers to precision of measurements. 
10Dissolved inorganic nutrients=NO3, PO4, SiO2.
11Dissolved oxygen is set to ‘core’ due to few available nutrient sensors.
12Dissolved inorganic nutrients=NO3, PO4, SiO2.