scholarly journals Stable water isotopes in the MITgcm

2017 ◽  
Vol 10 (8) ◽  
pp. 3125-3144 ◽  
Author(s):  
Rike Völpel ◽  
André Paul ◽  
Annegret Krandick ◽  
Stefan Mulitza ◽  
Michael Schulz
Keyword(s):  
Isotopic Composition ◽  
Observational Data ◽  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Deep Ocean ◽  
Sea Surface ◽  
Water Isotopes ◽  
Model Data ◽  
Stable Water Isotopes

Abstract. We present the first results of the implementation of stable water isotopes in the Massachusetts Institute of Technology general circulation model (MITgcm). The model is forced with the isotopic content of precipitation and water vapor from an atmospheric general circulation model (NCAR IsoCAM), while the fractionation during evaporation is treated explicitly in the MITgcm. Results of the equilibrium simulation under pre-industrial conditions are compared to observational data and measurements of plankton tow records (the oxygen isotopic composition of planktic foraminiferal calcite). The broad patterns and magnitude of the stable water isotopes in annual mean seawater are well captured in the model, both at the sea surface as well as in the deep ocean. However, the surface water in the Arctic Ocean is not depleted enough, due to the absence of highly depleted precipitation and snowfall. A model–data mismatch is also recognizable in the isotopic composition of the seawater–salinity relationship in midlatitudes that is mainly caused by the coarse grid resolution. Deep-ocean characteristics of the vertical water mass distribution in the Atlantic Ocean closely resemble observational data. The reconstructed δ18Oc at the sea surface shows a good agreement with measurements. However, the model–data fit is weaker when individual species are considered and deviations are most likely attributable to the habitat depth of the foraminifera. Overall, the newly developed stable water isotope package opens wide prospects for long-term simulations in a paleoclimatic context.

scholarly journals Stable water isotopes in the MITgcm (checkpoint 64w)

2017 ◽  
Author(s):  
Rike Völpel ◽  
André Paul ◽  
Annegret Krandick ◽  
Stefan Mulitza ◽  
Michael Schulz
Keyword(s):  
Isotopic Composition ◽  
Observational Data ◽  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Deep Ocean ◽  
Oxygen Isotopic Composition ◽  
Water Isotopes ◽  
Stable Water Isotopes ◽  
Oxygen Isotopic

Abstract. We present the first results of the implementation of stable water isotopes in the ocean general circulation model MITgcm. The model is forced with the isotopic content of precipitation and water vapor from an atmospheric general circulation model (NCAR IsoCAM), while the fractionation during evaporation is treated explicitly in the MITgcm. Results of the equilibrium simulation under pre-industrial conditions are compared to observational data and paleoclimate records (the oxygen isotopic composition of planktic foraminiferal calcite). The broad patterns and magnitude of the stable water isotopes in annual mean seawater are well captured in the model, both at the sea surface as well as in the deep ocean. However, the surface water in the Arctic Ocean is not depleted enough, due to the absence of highly depleted precipitation and snow fall and slightly enriched river runoff. This shortcoming is also recognizable in the isotopic composition of the seawater-salinity relationship in mid-latitudes. Deep ocean characteristics of the vertical water mass distribution in the Atlantic Ocean closely resemble observational data. Apart from the systematic offset of the modeled oxygen isotopic composition of planktic foraminiferal calcite towards lower values, the comparison with proxy data shows a good agreement. We summarize that the offset is mainly caused by gametogenic calcification and a matter of choice of the applied paleotemperature equation. Overall, the newly developed stable water isotope package opens wide prospects for long-term simulations in a paleoclimatic context.

scholarly journals Wind-Generated Power Input to the Deep Ocean: An Estimate Using a 1/10° General Circulation Model

2007 ◽  
Vol 37 (3) ◽  
pp. 657-672 ◽  
Author(s):  
Jin-Song von Storch ◽  
Hideharu Sasaki ◽  
Jochem Marotzke
Keyword(s):  
General Circulation Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
Deep Ocean ◽  
Power Input ◽  
Ocean General Circulation Model ◽  
Sea Surface ◽  
Total Power ◽  
The Earth

Abstract Recent studies on the wind-generated power input to the geostrophic and nongeostrophic ocean circulation components have used expressions derived from Ekman dynamics. The present work extends and unifies previous studies by deriving an expression from the kinetic energy budget of the upper layer based on the primitive equations. Using this expression, the wind-generated power available to the deep ocean is estimated from an integration with the 1/10° ocean general circulation model of the Earth Simulator Center. The result shows that the total power generated by the wind at the sea surface is about 3.8 TW. About 30% of this power (1.1 TW) is passed through a surface layer of about 110-m thickness to the ocean beneath. Approximating the wind-generated power to the deep ocean using Ekman dynamics produces two large errors of opposite signs, which cancel each other to a large extent.

scholarly journals Simulating the mid-Pliocene climate with the MIROC general circulation model: experimental design and initial results

2011 ◽  
Vol 4 (4) ◽  
pp. 1035-1049 ◽  
Author(s):  
W.-L. Chan ◽  
A. Abe-Ouchi ◽  
R. Ohgaito
Keyword(s):  
Experimental Design ◽  
Boundary Conditions ◽  
General Circulation Model ◽  
General Circulation ◽  
Climate Models ◽  
Circulation Model ◽  
Sea Surface ◽  
Future Climate Change ◽  
Model Intercomparison ◽  
Initial Results

Abstract. Recently, PlioMIP (Pliocene Model Intercomparison Project) was established to assess the ability of various climate models to simulate the mid-Pliocene warm period (mPWP), 3.3–3.0 million years ago. We use MIROC4m, a fully coupled atmosphere-ocean general circulation model (AOGCM), and its atmospheric component alone to simulate the mPWP, utilizing up-to-date data sets designated in PlioMIP as boundary conditions and adhering to the protocols outlined. In this paper, a brief description of the model is given, followed by an explanation of the experimental design and implementation of the boundary conditions, such as topography and sea surface temperature. Initial results show increases of approximately 10°C in the zonal mean surface air temperature at high latitudes accompanied by a decrease in the equator-to-pole temperature gradient. Temperatures in the tropical regions increase more in the AOGCM. However, warming of the AOGCM sea surface in parts of the northern North Atlantic Ocean and Nordic Seas is less than that suggested by proxy data. An investigation of the model-data discrepancies and further model intercomparison studies can lead to a better understanding of the mid-Pliocene climate and of its role in assessing future climate change.

scholarly journals Controls on the water vapor isotopic composition near the surface of tropical oceans and role of boundary layer mixing processes

2019 ◽  
Author(s):  
Camille Risi ◽  
Joseph Galewsky ◽  
Gilles Reverdin ◽  
Florent Brient
Keyword(s):  
Water Vapor ◽  
Isotopic Composition ◽  
General Circulation ◽  
Model Simulation ◽  
Circulation Model ◽  
Sea Surface ◽  
Trade Wind ◽  
Mixing Processes ◽  
Tropical Oceans ◽  
Air Mixing

Abstract. Understanding what controls the water vapor isotopic composition of the sub-cloud layer (SCL) over tropical oceans (δD0) is a first step towards understanding the water vapor isotopic composition everywhere in the troposphere. We propose an analytical model to predict δD0 as a function of sea surface conditions, humidity and temperature profiles, and the altitude from which the free tropospheric air originates (zorig). To do so, we extend previous studies by (1) prescribing the shape of δD0 vertical profiles, and (2) linking δD0 to zorig. The model relies on the hypotheses that δD0 profiles are steeper than mixing lines and no clouds are precipitating. We show that δD0 does not depend on the intensity of entrainment, dampening hope that δD0 measurements could help constrain this long-searched quantity. Based on an isotope-enabled general circulation model simulation, we show that δD0 variations are mainly controlled by mid-tropospheric depletion and rain evaporation in ascending regions, and by sea surface temperature and zorig in subsiding regions. When the air mixing into the SCL is lower in altitude, it is moister, and thus it depletes more efficiently the SCL. In turn, could δD0 measurements help estimate zorig and thus discriminate between different mixing processes? Estimates that are accurate enough to be useful would be difficult to achieve in practice, requiring measuring daily δD profiles, and measuring δD0 with an accuracy of 0.1 ‰ and 0.4 ‰ in trade-wind cumulus and strato-cumulus clouds respectively.

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