On the deep western-boundary current in the Southwest Pacific Basin

Whitworth, Thomas; Warren, Bruce A.; Nowlin, Worth D.; Rutz, S.B; Pillsbury, R.D.; Moore, Mike I.

doi:10.1016/s0079-6611(99)00005-1

Cited by 120 publications

(115 citation statements)

References 47 publications

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“…An upwelling of 4 m/yr corresponds to a downwelling/upwelling of water into the deep oceans of about 45 Sv (1 Sv = 10 6 m 3 /s). This value is higher, in general, than downwelling estimates based on observations presented in Harvey (1996), Munk andWunsch (1998), andWhitworth et al (1999), but in line with upwelling estimates presented in Whitworth et al (1999), and a standard assumption in many other UDEBM, see for example Munk (1966), Hoffert et al (1980), Harvey and Huang (2001), Wigley and Raper (2001), Lowe et al (2009), andMeinshausen et al (2009). In order to analyze different rates of ocean heat uptake, different values for the effective heat diffusivity is assumed.…”

Section: Energy Balance Modelsupporting

confidence: 72%

Temperature stabilization, ocean heat uptake and radiative forcing overshoot profiles

Johansson

2010

Climatic Change

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Political leaders in numerous nations argue for an upper limit of the global average surface temperature of 2 K above the pre-industrial level, in order to attempt to avoid the most serious impacts of climate change. This paper analyzes what this limit implies in terms of radiative forcing, emissions pathways and abatement costs, for a range of assumptions on rate of ocean heat uptake and climate sensitivity.The primary aim is to analyze the importance of ocean heat uptake for radiative forcing pathways that temporarily overshoot the long-run stabilization forcing, yet keep the temperature increase at or below the 2 K limit. In order to generate such pathways, an integrated climate-economy model, MiMiC, is used, in which the emissions pathways generated represent the least-cost solution of stabilizing the global average surface temperature at 2 K above the pre-industrial level. We find that the level of overshoot can be substantial. For example, the level of overshoot in radiative forcing in 2100 ranges from about 0.2 to 1 W/m 2 , where the value depends strongly and positively on the effective diffusivity of heat in the oceans. Measured in relative terms, the level of radiative forcing overshoot above its longrun equilibrium level in 2100 is 20% to 60% for high values of climate sensitivity (i.e., about 4.5 K) and 8% to 30% for low values of climate sensitivity (i.e., about 2 K). In addition, for cases in which the radiative forcing level can be directly stabilized at the equilibrium level associated with a specific climate sensitivity and the 2 K limit, the net present value abatement cost is roughly cut by half if overshoot pathways are considered instead of stabilization of radiative forcing at the equilibrium level without an overshoot.

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Section: Energy Balance Modelsupporting

confidence: 72%

Temperature stabilization, ocean heat uptake and radiative forcing overshoot profiles

Johansson

2010

Climatic Change

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“…Stommel and Arons (1960) first explored the consequences of this statement by assuming a uniform upwelling rate at the base of the main thermocline, and showing that this would govern a Sverdrup-like circulation in the interior, from which they inferred the necessary existence of deep westernboundary currents accomplishing interbasin mass transport. The existence and directions of these currents had been suggested by laboratory experiments Stommel et al (1958) and was later confirmed by in situ measurements (see Arhan et al (1998); Whitworth et al (1999) and references therein). In this framework, the driving force of the abyssal circulation is the downward diffusion of heat, which controls the global upwelling rate, thereby setting the magnitude of the meridional overturning circulation (MOC).…”

Section: Introductionmentioning

confidence: 70%

Geothermal heating, diapycnal mixing and the abyssal circulation

Emile‐Geay

Madec

2009

Ocean Sci.

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Abstract. The dynamical role of geothermal heating in abyssal circulation is reconsidered using three independent arguments. First, we show that a uniform geothermal heat flux close to the observed average (86.4 mW m −2 ) supplies as much heat to near-bottom water as a diapycnal mixing rate of ∼10 −4 m 2 s −1 -the canonical value thought to be responsible for the magnitude of the present-day abyssal circulation. This parity raises the possibility that geothermal heating could have a dynamical impact of the same order. Second, we estimate the magnitude of geothermally-induced circulation with the density-binning method (Walin, 1982), applied to the observed thermohaline structure of Levitus (1998). The method also allows to investigate the effect of realistic spatial variations of the flux obtained from heatflow measurements and classical theories of lithospheric cooling. It is found that a uniform heatflow forces a transformation of ∼6 Sv at σ 4 =45.90, which is of the same order as current best estimates of AABW circulation. This transformation can be thought of as the geothermal circulation in the absence of mixing and is very similar for a realistic heatflow, albeit shifted towards slightly lighter density classes. Third, we use a general ocean circulation model in global configuration to perform three sets of experiments: (1) a thermally homogenous abyssal ocean with and without uniform geothermal heating; (2) a more stratified abyssal ocean subject to (i) no geothermal heating, (ii) a constant heat flux of 86.4 mW m −2 , (iii) a realistic, spatially varying heat flux of identical global average; (3) experiments (i) and (iii) with enhanced vertical mixing at depth. Geothermal heating and diapycnal mixing are found to interact non-linearly through the density field, with geothermal heating eroding the deep stratification supporting a downward diffusive flux, while diapycnal mixing acts to map near-surface temperature gradientsCorrespondence to: J. Emile-Geay (julieneg@usc.edu) onto the bottom, thereby altering the density structure that supports a geothermal circulation. For strong vertical mixing rates, geothermal heating enhances the AABW cell by about 15% (2.5 Sv) and heats up the last 2000 m by ∼0.15 • C, reaching a maximum of by 0.3 • C in the deep North Pacific. Prescribing a realistic spatial distribution of the heat flux acts to enhance this temperature rise at mid-depth and reduce it at great depth, producing a more modest increase in overturning than in the uniform case. In all cases, however, poleward heat transport increases by ∼10% in the Southern Ocean. The three approaches converge to the conclusion that geothermal heating is an important actor of abyssal dynamics, and should no longer be neglected in oceanographic studies.

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“…Although there are many methods to estimate the upwelling rate (for example, Kuo and Veronis 1973;Stuiver et al 1983;Robbins and Toole 1997), they are not consistent with one another. These estimations are open to criticism and are somewhat questionable (Whitworth et al 1999). Further study including more complete dynamics and realistic upwelling velocity should be helpful for understanding the relationship between the upper layer circulation and the deep circulation of the SCS.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…However, observations suggest that upwelling is nonuniform (Whitworth et al 1999). Because the upwelling velocity is too small to measure directly, it has been estimated by various indirect means (Kuo and Veronis 1973;Stuiver et al 1983;Robbins and Toole, 1997).…”

Section: B Determination Of the Abyssal Vertical Velocity Distributionmentioning

confidence: 99%

The Effects of Thermohaline Circulation on Wind-Driven Circulation in the South China Sea

Wang

Huang

et al. 2012

Journal of Physical Oceanography

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The dynamic influence of thermohaline circulation on wind-driven circulation in the South China Sea (SCS) is studied using a simple reduced gravity model, in which the upwelling driven by mixing in the abyssal ocean is treated in terms of an upward pumping distributed at the base of the upper layer.Because of the strong upwelling of deep water, the cyclonic gyre in the northern SCS is weakened, but the anticyclonic gyre in the southern SCS is intensified in summer, while cyclonic gyres in both the southern and northern SCS are weakened in winter. For all seasons, the dynamic influence of thermohaline circulation on wind-driven circulation is larger in the northern SCS than in the southern SCS. Analysis suggests that the upwelling associated with the thermohaline circulation in the deep ocean plays a crucial role in regulating the wind-driven circulation in the upper ocean.

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On the deep western-boundary current in the Southwest Pacific Basin

Cited by 120 publications

References 47 publications

Temperature stabilization, ocean heat uptake and radiative forcing overshoot profiles

Temperature stabilization, ocean heat uptake and radiative forcing overshoot profiles

Geothermal heating, diapycnal mixing and the abyssal circulation

The Effects of Thermohaline Circulation on Wind-Driven Circulation in the South China Sea

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