Pacific Ocean ratios

Fig. 18-1 Benthic foraminiferal oxygen isotope record from 3477 m water depth in the eastern tropical Pacific ocean from Ocean Drilling Program site 677 (Shackleton et al, 1990). ratios are expressed in the S...

Vertical concentration profiles of (a) temperature, (b) potential density, (c) salinity, (d) O2, (e) % saturation of O2, (f) bicarbonate and TDIC, (g) carbonate alkalinity and total alkalinity, (h) pH, (i) carbonate, ( ) carbon dioxide and carbonic acid concentrations, and (k) carbonate-to-bicarbonate ion concentration ratio. Curves labeled f,p have been corrected for the effects of in-situ temperature and pressure on equilibrium speciation. Curves labeled t, 1 atm have been corrected for the in-situ temperature effect, but not for that caused by pressure. Data from 50°27.5 N, 176°13.8 W in the North Pacific Ocean on June 1966. Source From Culberson, C., and R. M. Pytkowicz (1968). Limnology and Oceanography, 13, 403-417. 

North Atlantic Deep Water (NADW), which is formed with an initial 5 C-value between 1.0 and 1.5%c, becomes gradually depleted in C as it travels southward and mixes with Antarctic bottom water, which has an average 8 C-value of 0.3%c (Kroopnick 1985). As this deep water travels to the Pacific Ocean, its C/ C ratio is further reduced by 0.5%o by the continuous flux and oxidation of organic matter in the water column. This is the basis for using 8 C-values as a tracer of paleo-oceanographic changes in deep water circulation (e.g., Curry et al. 1988). 

Figure 12.6 Vertical distributions of Group 4 elements in the North Pacific. Data sources Ti (Orians et at., 1990), Zr (McKelvey and Orians, 1993) and Hf (Godfrey et at., 1996). The Hf distribution (dotted line) was calculated based on the average Atlantic Ocean Zr/Hf ratio of Godfrey et at. (1996) and the Pacific Ocean Zr profile of McKelvey and Orians (1993).

Bernstein, R.E., Betzer, PR., Feely, R.A., Byrne, R.H., Lamb, M.F. and Michaels, A.F. (1987) Acantharian fluxes and strontium to chlorinity ratios in the north Pacific Ocean. Science, 237,1490-1494. 

Uppstrom, L.R. (1974) Boron/chlorinity ratio of deep-sea water from the Pacific Ocean. Deep-Sea Res., 21, 105-116. 

Figure 18. Ratio of measured rates of dissolution per gram to the initial dissolution for pteropods and calcite Pacific Ocean sediment (57)...

Only occasionally has the N content of solid phase extracts been reported. At a site in the Atlantic Ocean the carbon to nitrogen ratio (C N) of XAD 8 and XAD 2 extracts fell in the range of 40-57 (57 0.9 and 41.1 3.3, respectively DrufFel et ai, 1992). In contrast, at the same site XAD 4, when used as the second resin in series with XAD 8 or XAD 2, extracted compounds with lower C N ratios - 19—24 (21.0 2.4). These values are only slighdy higher than ratios reported for total DOM (see below). McKnight and Aiken (1998) reported a C N value of 37 for DOM extracted by XAD 8 at one site in the Pacific Ocean at other sites in the N. Pacific Ocean XAD 2 was found to extract DOM with a C N ratio between 32 and 46.5 (Druffel et al, 1992 Meyers-Schulte and Hedges, 1986). Bronk (2002, Table III) compiled various literature values and arrived at an average C N ratio of 32.8 19.5 for total humic substances isolated from a variety of aqueous environments (see McCarthy and Bronk, this volume). 

Values discussed in the previous section represent an oceanic average and individual regions and parts of the water column may behave differendy. For example, Abell et al. (2000, 2005) found that the DOM reminerahzed along isopycnals outcropping in the subtropical North Pacific Ocean is C-rich (C N 30) based on this C N ratio these authors concluded that DOM contributes between 70 and 90% of the total organic matter remineralized in the upper thermocHne. As more data are collected, other sites in the ocean may show similar variabiHty. 

For example, an extensive 9-year data set from ALOFLA indicates that the bulk dissolved matter N P ratio is variable. In the subtropical North Pacific Ocean, N2 fixation may supply up to half of the new N to sustain the rate of the annual particulate N export from the euphoric zone. A recent increase in this source of new N appears to have shifted the North Pacific subtropical gyre from N Hmitation to P hmitation (Karl et al., 1997). Hence in the ohgotrophic ocean, N2 fixation could lead to a decoupling of N and P pool dynamics and an alternation of N versus P control of primary production (Karl et al., 2001). Similarly but on a shorter time-frame, in the central Baltic Sea the development of N2-fixing cyanobacterial blooms can drive the system from N limitation to P hmitation between May to September (Nausch et al., 2004). 

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