Deep Pacific Circulation Controlled by Vertical Diffusivity at the Lower Thermocline Depths

Tsujino, Hiroyuki; Hasumi, Hiroyasu; Suginohara, Nobuo

doi:10.1175/1520-0485(2001)031<2853:dpccbv>2.0.co;2

Cited by 99 publications

(85 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Of all the simulations studied, only T00 and TideNF seem to capture the Pacific THC realistically. These results support those obtained in a previous study 16 , which indicates that the value of Kv around the thermocline (B1,000-3,000 m) is key to controlling the strength of the Pacific THC. Figure 2 shows the Pacific meridional overturning stream function in each simulation.…”

Section: Resultssupporting

confidence: 91%

“…The vertical profile of Kv, applied in TideN (only near-field mixing is included as in previous parameterization) and TideNF (our new parameterization: both near-field and far-field mixing are included) simulations, is displayed in Fig. 1c, which also illustrates several other profiles that are commonly used: a classical one-dimensional profile (BL) 15 , a modified one-dimensional profile (T00) 16 and a roughness diffusion model (DL10) 17 . The T00 profile has larger Kv values below the thermocline than the BL profile.…”

Section: Resultsmentioning

confidence: 99%

“…4c). As the value of Kv around the thermocline is important for driving the Pacific THC 16 , near-field dissipation takes place too close to the sea bottom in order to drive the Pacific THC where h ¼ 100 m. Conversely, the tidal dissipation can drive the Pacific THC with sufficient efficiency for h ¼ 2,000 m, and simulation with q ¼ 1 can reproduce the D 14 C distribution as well as the TideNF simulation (similar to that shown in Fig. 3f).…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Pacific deep circulation and ventilation controlled by tidal mixing away from the sea bottom

Oka

Niwa

2013

Nat Commun

View full text Add to dashboard Cite

Vertical mixing in the ocean is a key driver of the global ocean thermohaline circulation, one of the most important factors controlling past and future climate change. Prior observational and theoretical studies have focused on intense tidal mixing near the sea bottom (near-field mixing). However, ocean general circulation models that employ a parameterization of nearfield mixing significantly underestimate the strength of the Pacific thermohaline circulation. Here we demonstrate that tidally induced mixing away from the sea bottom (far-field mixing) is essential in controlling the Pacific thermohaline circulation. Via the addition of far-field mixing to a widely used tidal parameterization, we successfully simulate the Pacific thermohaline circulation. We also propose that far-field mixing is indispensable for explaining the presence of the world ocean's oldest water in the eastern North Pacific Ocean. Our findings suggest that far-field mixing controls ventilation of the deep Pacific Ocean, a process important for ocean carbon and biogeochemical cycles.

show abstract

Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Pacific deep circulation and ventilation controlled by tidal mixing away from the sea bottom

Oka

Niwa

2013

Nat Commun

View full text Add to dashboard Cite

show abstract

“…Antarctic Bottom Water, mixing with North Atlantic Deep Water, forms the lower Circumpolar Deep Water, some of which escapes to the north, first encountering the Kermadec Trench and the Tonga Trench (49,52). There, strains acquiring mutations enhancing their fitness at that depth could reproduce, and their descendants could then hitchhike on the "global conveyor belt" (49,52) of deepwater circulation to other trenches. This dispersal mechanism could also explain the apparent paradox of the similarity between Arctic and Antarctic psychrophilic bacterial communities (48).…”

Section: Resultsmentioning

confidence: 99%

The Unique 16S rRNA Genes of Piezophiles Reflect both Phylogeny and Adaptation

Lauro

Chastain

Blankenship

et al. 2007

Appl Environ Microbiol

124

View full text Add to dashboard Cite

In the ocean's most extreme depths, pressures of 70 to 110 megapascals prevent the growth of all but the most hyperpiezophilic (pressure-loving) organisms. The physiological adaptations required for growth under these conditions are considered to be substantial. Efforts to determine specific adaptations permitting growth at extreme pressures have thus far focused on relatively few ␥-proteobacteria, in part due to the technical difficulties of obtaining piezophilic bacteria in pure culture. Here, we present the molecular phylogenies of several new piezophiles of widely differing geographic origins. Included are results from an analysis of the first deep-trench bacterial isolates recovered from the southern hemisphere (9.9-km depth) and of the first grampositive piezophilic strains. These new data allowed both phylogenetic and structural 16S rRNA comparisons among deep-ocean trench piezophiles and closely related strains not adapted to high pressure. Our results suggest that (i) the Circumpolar Deep Water acts as repository for hyperpiezophiles and drives their dissemination to deep trenches in the Pacific Ocean and (ii) the occurrence of elongated helices in the 16S rRNA genes increases with the extent of adaptation to growth at elevated pressure. These helix changes are believed to improve ribosome function under deep-sea conditions. Low temperature and high hydrostatic pressure structure deep-sea communities outside of hydrothermal vents. Tight selection by these and other environmental parameters is considered the cause of the conspicuous absence of many deep-sea taxonomic groups from the deepest ocean environments (8, 44).Both temperature and pressure exert their effects at many levels of bacterial physiology, from the structure of macromolecules to the rate of metabolic reactions. Adaptations to low temperature include alterations of membrane phospholipids, such as increased fatty acid unsaturation (43), enzymes characterized by high catalytic efficiency and reduced activation enthalpy (16,20,37,45), and high levels of cold shock proteins, RNA helicases (9), and posttranscriptional modification of tRNA molecules (15), all of which may reduce the formation of unfavorable nucleic acid secondary structures at low temperature. In contrast with enthalpy-based temperature effects, the underlying cause of pressure effects arises from the promotion of reduced system volumes, in accordance with Le Chatelier's principle (5). Despite these thermodynamic differences, low temperature and high pressure share a surprising number of influences on biological processes. For example, membrane fluidity, permeability, and phase are similarly altered by both parameters.As with psychrophiles, piezophiles ("high-pressure-loving" microbes) contain lipids with highly unsaturated fatty acids (6, 7). Indeed, the presence of unsaturated fatty acids is critical to growth ability at high pressure (3,4,19). Both low temperature and high pressure also alter protein quaternary structure (46) and nucleic acid secondary structure (50), and at ...

show abstract

“…An eddy-mixing parameterization based on Gent and McWilliams (1990) is introduced, wherein the isopycnal-mixing coefficient is set uniformly to 2 Â 10 3 m 2 s À1 . The diapycnal-mixing coefficient has been modified in MRI2.3 to vary with depth, based on Tsujino et al (2000) as provided in Table 2; it was a constant 1 Â 10 À5 m 2 s À1 in MRI2.0. The vertical turbulence viscosity and diffusivity, were modeled following Mellor andYamada (1974, 1982), and Mellor and Durbin (1975) for the surface mixed layer, in addition to the isopycnal mixing.…”

Section: Ocean Componentmentioning

confidence: 99%

Present-Day Climate and Climate Sensitivity in the Meteorological Research Institute Coupled GCM Version 2.3 (MRI-CGCM2.3)

Yukimoto¹,

Noda²,

Hosaka³

et al. 2006

Journal of the Meteorological Society of Japan

122

View full text Add to dashboard Cite

A new version of the Meteorological Research Institute (MRI) coupled general circulation model MRI-CGCM2 (MRI2.3) is developed and compared with the previous version (MRI2.0). The cloud scheme includes diagnostic function for cloud amount separately specified for convective and layer clouds, which is one of the major modifications contributing to the improved model performance. MRI2.3 exhibits better agreement with the observations in many aspects of present-day climate simulations, including the global energy budget, meridional distributions of shortwave and longwave radiation at the top of the atmosphere, and geographical distributions of surface air temperature and precipitation. The effective climate sensitivity of each version is evaluated based on an experiment with a transient (1%/year) increase of carbon dioxide concentration. The effective climate sensitivity of MRI2.3 (2.9 K) is about twice that of MRI2.0 (1.4 K). The change in the cloud-forcing response, particularly for shortwave cloud forcing, is essential for increasing climate sensitivity. A difference in tropical low-level clouds over the subsidence regions contributes significantly to the difference in cloud-forcing changes in response to a climate change. Analyses based on circulation regimes, defined by the vertical velocity at the mid-troposphere, suggest that the cloud-forcing response in the tropics is controlled more by thermodynamic characteristics, such as changes of the stability in the lower troposphere, rather than by large-scale circulation changes, such as a change in the subsidence strength.

show abstract

Deep Pacific Circulation Controlled by Vertical Diffusivity at the Lower Thermocline Depths

Cited by 99 publications

References 28 publications

Pacific deep circulation and ventilation controlled by tidal mixing away from the sea bottom

Pacific deep circulation and ventilation controlled by tidal mixing away from the sea bottom

The Unique 16S rRNA Genes of Piezophiles Reflect both Phylogeny and Adaptation

Present-Day Climate and Climate Sensitivity in the Meteorological Research Institute Coupled GCM Version 2.3 (MRI-CGCM2.3)

Contact Info

Product

Resources

About