Unravelling the land source: an investigation of the processes contributing to the oceanic input of DIC and alkalinity

Figures & data

Fig. 1 Reservoirs and processes within the marine nitrogen cycle. The arrows represent exchange processes and the numbers are the associated alkalinity effects.

Fig. 2 Simplified representation of the marine nitrogen cycle. The ammonium is assumed instantly nitrified. The numbers coupled to the arrows are the alkalinity effect associated with each exchange process.

Fig. 3 Simplified representation of the marine nitrogen cycle. The ammonium is assumed to be nitrified as in Fig. 2. Furthermore, the organic nitrogen reservoir is assumed small compared to the nitrate reservoir.

Table 1. Effect of the different processes on DIC and alkalinity. Units of moles for DIC and equivalents for alkalinity

Process	Species	Atmosphere	Ocean	Total
CaCO3 weathering (per mole Ca^2+)	DIC/CO2	−1	+2	+1
	Alk	–	+2	+2
Silicate weathering (per mole Ca^2+ or Mg^2+)	DIC/CO2	−2	+2	0
	Alk	–	+2	+2
Pyrite weathering (per mole S)	DIC/CO2	0	0	0
	Alk	–	−2	−2
Fossil C weathering (per mole C)	DIC/CO2	0/+1	+1/0	+1
	Alk	–	0	0
Aerial (per mole S)	DIC/CO2	0	0	0
	Alk	–	−2	−2
Riverine (per mole N)	DIC/CO2	0	0	0
	Alk	–	−1	−1
Riverine (per mole N)	DIC/CO2	0	0	0
	Alk	–	+1	+1
Organic matter erosion (per mole C)	DIC/CO2	−1	+1	0
	Alk	–	0	0

Table 2. Riverine fluxes of different ions, Particulate and Dissolved Organic Carbon (POC, DOC) and Total Dissolved Nitrogen (TDN)

Species	Size [Tmol yr^−1]	Reference
Na+	8.38	Meybeck (1979)
K+	1.23	Meybeck (1979)
Ca^2+	12.5	Meybeck (1979)
Mg^2+	5.16	Meybeck (1979)
	31.9	Meybeck (1979)
Cl^−	6.07	Meybeck (1979)
	3.21	Meybeck (1979)
SiO2	6.25	Meybeck (1979)
	0.267	Meybeck (1993b)
	0.040	Meybeck (1993b)
POC	11.7	Seitzinger et al. (2010)
DOC	13.7	Seitzinger et al. (2010)
TDN	3.03	Mackenzie and Lerman (1993)

Table 3. Riverine fluxes of dissolved species due to different processes. Also included are ocean floor burial of pyrite and organic carbon

Process	Size [Tmolyr^−1]	Species	Reference
Carbonate weathering	12.5/7.5		Berner et al. (1983); Ludwig et al. (1996)
Silicate weathering	5.9/5.8		Berner et al. (1983); Ludwig et al. (1996)
Pyrite weathering	0.64	S	Lerman et al. (2007)
Pyrite burial	1.22	S	Berner (1982)
Org. C burial	10.5	C	Berner (1982)
Aerial	1.1	S	Berner and Berner (2012)
Riverine nitrate	0.27	N	Meybeck (1993b)
Riverine	0.04	N	Meybeck (1993b)

Table 4. Total river fluxes of DIC derived from different processes together with the internal and external components. Also shown are examples of models that include a certain process

Flux derived from	Total river flux [TmolC yr^−1]	Internal component [TmolC yr^−1]	External component [TmolC yr^−1]	Models that include the flux
Carbonate weathering	25.0^a/15.0^b	12.5^a/7.50^b	12.5^a/7.50^b	Zeebe (2012); Arvidson et al. (2006); Shaffer et al. (2008); Chuck et al. (2005); Goddéris et al. (2001)
Silicate weathering	11.8^a/11.6^b	11.8^a/11.6^b	0	Shaffer et al. (2008); Goddéris et al. (2001); Arvidson et al. (2006); Walker and Kasting (1992)
Fossil C weathering	10.5^1	0	10.5^1	Walker and Kasting (1992); Arvidson et al. (2006); Goddéris et al. (2001)
Organic matter erosion	25.4	16.7^2	−8.7^3	Chuck et al. (2005)

^aBerner et al. (1983).

^bLudwig et al. (1996).

¹Weathering of fossil carbon is somewhat arbitrarily assumed equal to organic carbon burial (see Table 3). Note that this carbon can just as well be released directly to the atmosphere (cf. Kump and Arthur, 1999; Walker and Kasting, 1992).

²Oxidation of terrigenous TOC.

³Burial of terrestrial organic carbon in the ocean.

Table 5. Alkalinity fluxes due to different processes together with models that include a certain process

Flux derived from	Total flux (T eq yr^−1)	Models that include the flux
Carbonate weathering	25.0^a/15.0^b	Zeebe (2012); Arvidson et al. (2006); Shaffer et al. (2008); Chuck et al. (2005); Goddéris et al. (2001); Walker and Kasting (1992)
Silicate weathering	11.8^a/11.6^b	Shaffer et al. (2008); Arvidson et al. (2006); Walker and Kasting (1992); Goddéris et al. (2001)
Pyrite weathering	−1.28	Arvidson et al. (2006); Goddéris et al. (2001)
Aerial	−2.2	Doney et al. (2007)
Riverine	0.27	Chuck et al. (2005)
Riverine	−0.04

^aBerner et al. (1983).

^bLudwig et al. (1996).

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