Inter-annual tropical Pacific climate variability in an isotope-enabled CGCM: implications for interpreting coral stable oxygen isotope records of ENSO

Abstract. Water isotope-enabled coupled atmosphere/ocean climate models allow for exploration of the relative contributions to coral stable oxygen isotope (δ18Ocoral) variability arising from Sea Surface Temperature (SST) and the isotopic composition of seawater (δ18Osw). The unforced behaviour of the isotope-enabled HadCM3 Coupled General Circulation Model affirms that the extent to which inter-annual δ18Osw variability contributes to that in model δ18Ocoral is strongly spatially dependent, ranging from being negligible in the eastern equatorial Pacific to accounting for 50% of δ18Ocoral variance in parts of the western Pacific. In these latter cases, a significant component of the inter-annual δ18Osw variability is correlated to that in SST, meaning that local calibrations of the effective local δ18Ocoral–SST relationships are likely to be essential. Furthermore, the relationship between δ18Osw and SST in the central and western equatorial Pacific is non-linear, such that the interpretation of model δ18Ocoral in the context of a linear dependence on SST alone may lead to overestimation (by up to 20%) of the SST anomalies associated with large El-Niño events. Intra-model evaluation of a salinity-based pseudo-coral approach shows that such an approach captures the first-order features of the model δ18Osw behaviour. However, the utility of the pseudo-corals is limited by the extent of spatial variability seen within the modelled slopes of the temporal salinity–δ18Osw relationship.

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Inter-annual tropical Pacific climate variability in an isotope-enabled CGCM: implications for interpreting coral stable oxygen isotope records of ENSO

Climate of the Past ◽

10.5194/cp-9-1543-2013 ◽

2013 ◽

Vol 9 (4) ◽

pp. 1543-1557 ◽

Cited By ~ 22

Author(s):

T. Russon ◽

A. W. Tudhope ◽

G. C. Hegerl ◽

M. Collins ◽

J. Tindall

Keyword(s):

Oxygen Isotope ◽

General Circulation ◽

Climate Models ◽

Circulation Model ◽

Equatorial Pacific ◽

Stable Oxygen Isotope ◽

Model Interpretation ◽

Eastern Equatorial Pacific ◽

Stable Oxygen ◽

Pacific Climate Variability

Abstract. Water isotope-enabled coupled atmosphere–ocean climate models allow for exploration of the relative contributions to coral stable oxygen isotope (δ18Ocoral) variability arising from sea surface temperature (SST) and the isotopic composition of seawater (δ18Osw). The unforced behaviour of the isotope-enabled HadCM3 coupled general circulation model suggests that the extent to which inter-annual δ18Osw variability contributes to that in model δ18Ocoral is strongly spatially dependent, ranging from being negligible in the eastern equatorial Pacific to accounting for 50% of δ18Ocoral variance in parts of the western Pacific. In these latter cases, a significant component of the inter-annual δ18Osw variability is correlated to that in SST, meaning that local calibrations of the effective local δ18Ocoral–SST relationships are likely to be essential. Furthermore, the relationship between δ18Osw and SST can be non-linear, such that the model interpretation of central and western equatorial Pacific δ18Ocoral in the context of a linear dependence on SST alone leads to overestimation (by up to 20%) of the SST anomalies associated with large El Niño events. Intra-model evaluation of a salinity-based pseudo-coral approach shows that such an approach captures the first-order features of the model δ18Osw behaviour. However, the utility of the pseudo-corals is limited by the extent of spatial variability seen within the modelled slopes of the temporal salinity–δ18Osw relationship.

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Near-Annual SST Variability in the Equatorial Pacific in a Coupled General Circulation Model

Journal of Climate ◽

10.1175/jcli3536.1 ◽

2005 ◽

Vol 18 (21) ◽

pp. 4454-4473 ◽

Cited By ~ 6

Author(s):

Renguang Wu ◽

Ben P. Kirtman

Keyword(s):

General Circulation ◽

Circulation Model ◽

Equatorial Pacific ◽

Near Surface ◽

Boreal Spring ◽

Eastern Equatorial Pacific ◽

Zonal Advection ◽

The Mean ◽

Annual Mode ◽

Sst Anomalies

Abstract Equatorial Pacific sea surface temperature (SST) anomalies in the Center for Ocean–Land–Atmosphere Studies (COLA) interactive ensemble coupled general circulation model show near-annual variability as well as biennial El Niño–Southern Oscillation (ENSO) variability. There are two types of near-annual modes: a westward propagating mode and a stationary mode. For the westward propagating near-annual mode, warm SST anomalies are generated in the eastern equatorial Pacific in boreal spring and propagate westward in boreal summer. Consistent westward propagation is seen in precipitation, surface wind, and ocean current. For the stationary near-annual mode, warm SST anomalies develop near the date line in boreal winter and decay locally in boreal spring. Westward propagation of warm SST anomalies also appears in the developing year of the biennial ENSO mode. However, warm SST anomalies for the westward propagating near-annual mode occur about two months earlier than those for the biennial ENSO mode and are quickly replaced by cold SST anomalies, whereas warm SST anomalies for the biennial ENSO mode only experience moderate weakening. Anomalous zonal advection contributes to the generation and westward propagation of warm SST anomalies for both the westward propagating near-annual mode and the biennial ENSO mode. However, the role of mean upwelling is markedly different. The mean upwelling term contributes to the generation of warm SST anomalies for the biennial ENSO mode, but is mainly a damping term for the westward propagating near-annual mode. The development of warm SST anomalies for the stationary near-annual mode is partially due to anomalous zonal advection and upwelling, similar to the amplification of warm SST anomalies in the equatorial central Pacific for the biennial ENSO mode. The mean upwelling term is negative in the eastern equatorial Pacific for the stationary near-annual mode, which is opposite to the ENSO mode. The development of cold SST anomalies in the aftermath of warm SST anomalies for the westward propagating near-annual mode is coupled to large easterly wind anomalies, which occur between the warm and cold SST anomalies. The easterly anomalies contribute to the cold SST anomalies through anomalous zonal, meridional, and vertical advection and surface evaporation. The cold SST anomalies, in turn, enhance the easterly anomalies through a Rossby-wave-type response. The above processes are most effective during boreal spring when the mean near-surface-layer ocean temperature gradient is the largest. It is suggested that the westward propagating near-annual mode is related to air–sea interaction processes that are limited to the near-surface layers.

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Origin and Pathway of Equatorial 13°C Water in the Pacific Identified by a Simulated Passive Tracer and Its Adjoint*

Journal of Physical Oceanography ◽

10.1175/2009jpo4045.1 ◽

2009 ◽

Vol 39 (8) ◽

pp. 1836-1853 ◽

Cited By ~ 32

Author(s):

Tangdong Qu ◽

Shan Gao ◽

Ichiro Fukumori ◽

Rana A. Fine ◽

Eric J. Lindstrom

Keyword(s):

General Circulation ◽

Circulation Model ◽

South Pacific ◽

Equatorial Region ◽

Equatorial Pacific ◽

Western Boundary ◽

Passive Tracer ◽

The South ◽

Mode Water ◽

Eastern Equatorial Pacific

Abstract The origin and pathway of the thermostad water in the eastern equatorial Pacific Ocean, often referred to as the equatorial 13°C Water, are investigated using a simulated passive tracer and its adjoint, based on circulation estimates of a global general circulation model. Results demonstrate that the source region of the 13°C Water lies well outside the tropics. In the South Pacific, some 13°C Water is formed northeast of New Zealand, confirming an earlier hypothesis on the water’s origin. The South Pacific origin of the 13°C Water is also related to the formation of the Eastern Subtropical Mode Water (ESTMW) and the Sub-Antarctic Mode Water (SAMW). The portion of the ESTMW and SAMW that eventually enters the density range of the 13°C Water (25.8 < σθ < 26.6 kg m−3) does so largely by mixing. Water formed in the subtropics enters the equatorial region predominantly through the western boundary, while its interior transport is relatively small. The fresher North Pacific ESTMW and Central Mode Water (CMW) are also important sources of the 13°C Water. The ratio of the southern versus the northern origins of the water mass is about 2 to 1 and tends to increase with time elapsed from its origin. Of the total volume of initially tracer-tagged water in the eastern equatorial Pacific, approximately 47.5% originates from depths above σθ = 25.8 kg m−3 and 34.6% from depths below σθ = 26.6 kg m−3, indicative of a dramatic impact of mixing on the route of subtropical water to becoming the 13°C Water. Still only a small portion of the water formed in the subtropics reaches the equatorial region, because most of the water is trapped and recirculates in the subtropical gyre.

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On the statistics of the zonal jets in the eastern equatorial Pacific and eastern North Pacific in an ensemble of eddy-resolving ocean general circulation model runs

Ocean Modelling ◽

10.1016/j.ocemod.2021.101761 ◽

2021 ◽

Vol 159 ◽

pp. 101761

Author(s):

Ryo Furue ◽

Masami Nonaka ◽

Hideharu Sasaki

Keyword(s):

General Circulation Model ◽

North Pacific ◽

General Circulation ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Equatorial Pacific ◽

Zonal Jets ◽

Eastern Equatorial Pacific ◽

Ocean General Circulation

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Effects of Climatological Model Biases on the Projection of Tropical Climate Change

Journal of Climate ◽

10.1175/jcli-d-15-0243.1 ◽

2015 ◽

Vol 28 (24) ◽

pp. 9909-9917 ◽

Cited By ~ 29

Author(s):

Zhen-Qiang Zhou ◽

Shang-Ping Xie

Keyword(s):

Climate Change ◽

Global Warming ◽

General Circulation ◽

Climate Models ◽

Circulation Model ◽

Walker Circulation ◽

Tropical Climate ◽

Equatorial Pacific ◽

Model Biases ◽

Tropical Climate Change

Abstract Climate models suffer from long-standing biases, including the double intertropical convergence zone (ITCZ) problem and the excessive westward extension of the equatorial Pacific cold tongue. An atmospheric general circulation model is used to investigate how model biases in the mean state affect the projection of tropical climate change. The model is forced with a pattern of sea surface temperature (SST) increase derived from a coupled simulation of global warming but uses an SST climatology derived from either observations or a coupled historical simulation. The comparison of the experiments reveals that the climatological biases have important impacts on projected changes in the tropics. Specifically, during February–April when the climatological ITCZ displaces spuriously into the Southern Hemisphere, the model overestimates (underestimates) the projected rainfall increase in the warmer climate south (north) of the equator over the eastern Pacific. Furthermore, the global warming–induced Walker circulation slowdown is biased weak in the projection using coupled model climatology, suggesting that the projection of the reduced equatorial Pacific trade winds may also be underestimated. This is related to the bias that the climatological Walker circulation is too weak in the model, which is in turn due to a too-weak mean SST gradient in the zonal direction. The results highlight the importance of improving the climatological simulation for more reliable projections of regional climate change.

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Chapter 25 The Response of the OSU two-level Atmospheric General Circulation model to a warm Sea-Surface Temperature Anomaly over the Eastern Equatorial Pacific Ocean

Coupled Ocean-Atmosphere Models - Elsevier Oceanography Series ◽

10.1016/s0422-9894(08)70721-9 ◽

1985 ◽

pp. 371-390 ◽

Cited By ~ 1

Author(s):

Steven K. Esbensen

Keyword(s):

Pacific Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

General Circulation ◽

Circulation Model ◽

Equatorial Pacific ◽

Equatorial Pacific Ocean ◽

Atmospheric General Circulation ◽

Eastern Equatorial Pacific ◽

Eastern Equatorial Pacific Ocean

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High-Resolution Climate Simulations of Oxygen Isotope Stage 3 in Europe

Quaternary Research ◽

10.1006/qres.2002.2374 ◽

2002 ◽

Vol 58 (3) ◽

pp. 296-309 ◽

Cited By ~ 97

Author(s):

Eric Barron ◽

David Pollard

Keyword(s):

Oxygen Isotope ◽

General Circulation ◽

Climate Models ◽

Mesoscale Model ◽

Circulation Model ◽

Sea Level Pressure ◽

Modeling Effort ◽

Oxygen Isotope Stage ◽

Model Driven ◽

Climate Simulations

AbstractOxygen isotope stage 3 (OIS 3) climate and its variations are the focus of the Stage 3 Project. The objective of the OIS 3 modeling effort is twofold: (1) to explore the importance of different boundary conditions on the climate of Europe and (2) to develop climate simulations that best reproduce the wealth of OIS 3 observations. Given the complexity of the topography and coastlines, the modeling effort is based on a “nested” General Circulation Model (GCM) and mesoscale model (RegCM2) with climate simulations for Europe on a 60-km grid spacing. The key conclusions are as follows: (1) The mesoscale model, driven by GCM output, does a reasonable job of reproducing the modern European climate. (2) OIS 3 variations in orbit, CO2, and ice-sheet size are of little significance in explaining the observed climate variability. (3) The model results focus attention on North Atlantic sea-surface temperatures (SST) as a major factor in explaining OIS 3 climates. (4) Experiments for different SST values capture a number of systematic changes in sea-level pressure and precipitation. (5) Climate models simulate substantial European cooling and significant changes in precipitation, but they do not explain large differences between OIS 3 warm and cold episodes.

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