Transient Tracers

	Transient tracers are man-made chemical compounds released to the atmosphere at known quantities that can be used in the ocean to quantify ventilation, transit time distribution and transport time-scales. Measurement of transient tracers in the subsurface ocean thus provides information on the time-scales since the ocean was ventilated, i.e. in contact with the atmosphere. A combination of these tracers provide the means to constrain the transit time distribution (TTD) of a water-mass that allows inference of concentrations or fates of other transient compounds, such as anthropogenic carbon or nitrous oxide.
	Domain:	Ocean
	Subdomain:	Biogeochemical
	Scientific Area:	Carbon Cycle and other GHGs
	ECV Steward:
	Products:	¹⁴C; SF₆; CFC-11; CFC-12

ECV Products and Requirements

These products and requirements reflect the Implementation Plan 2022 (GCOS-244).

The requirements are found in the complete 2022 ECVs Requirements document as well: ECV Transient Tracers.

Products			¹⁴C		SF₆			CFC-11		CFC-12
			Regional	Deep water formation areas	Regional	Deep water formation areas		Regional	Deep water formation areas	Regional	Deep water formation areas
	(*)	Unit	Values		Values		Unit	Values		Values
Horizontal Resolution	G	km	2000	200	2000	200	km	2000	200	2000	200
	B
	T		2000		2000			2000		2000
Vertical Resolution	G		-		-			-		-
	B		-		-			-		-
	T		-		-			-		-
Temporal Resolution	G	y	10	2	10	2	y	10	2	10	2
	B
	T		10		10			10		10
Timeliness	G	y	1		1		month	6		6
	B
	T		2		2			6		6
Required Measurement Uncertainty (2-sigma)	G	‰	1		0.4		‰	1		1
	B
	T		2
Stability	G		decadal	1y	decadal	1y		decadal	1y	decadal	1y
	B
	T		decadal		decadal			decadal		decadal

(*) Goal (G): an ideal requirement above which further improvements are not necessary. Breakthrough (B): an intermediate level between threshold and goal which, if achieved, would result in a significant improvement for the targeted application. The breakthrough value may also indicate the level at which specified uses within climate monitoring become possible. It may be appropriate to have different breakthrough values for different uses. Threshold (T): the minimum requirement to be met to ensure that data are useful

Data Sources

This list provides sources for openly accessible data sets with worldwide coverage for which metadata is available. It is curated by the respective GCOS ECV Steward(s). The list does not claim to be complete. Anyone with a suitable dataset who wishes it to be added to this list should contact the GCOS Secretariat.

Global Ocean Data Analysis Project (GLODAPv2):

http://glodap.info/

CLIVAR and Carbon Hydrographic Data Office (CCHDO):

http://cchdo.ucsd.edu/

National Centers for Environmental Information Ocean Carbon Data System (NCEI OCADS):

https://www.nodc.noaa.gov/ocads/

PANGAEA:

https://www.pangaea.de/