Mats Bentsen

Bjerknes Centre for Climate Research

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Ingo Bethke

University of Bergen

Helge Drange

University of Bergen

ØS

Øyvind Seland

Norwegian Meteorological Institute

Jerry Tjiputra

Bjerknes Centre for Climate Research

Mehmet Ilıcak

Istanbul Technical University

Chuncheng Guo

Bjerknes Centre for Climate Research

Christoph Heinze

Bjerknes Centre for Climate Research

Jens Boldingh Debernard

Norwegian Meteorological Institute

Trond Iversen

Norwegian Meteorological Institute

Alf Kirkevåg

Norwegian Meteorological Institute

Cooperative Institutions

Bjerknes Centre for Climate Research

University of Bergen

Centre National de la Recherche Scientifique

NSF National Center for Atmospheric Research

Nansen Environmental and Remote Sensing Center

NORCE Norwegian Research Centre

University of Oslo

Uni Research (Norway)

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

Chinese Academy of Sciences

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Response of the North Atlantic subpolar gyre to persistent North Atlantic oscillation like forcing

Climate Dynamics (2008)

Katja Lohmann Helge Drange Mats Bentsen

Atlantic Equatorial mode

Forcing (mathematics)

Tropical Atlantic

Gulf Stream

10.1007/s00382-008-0467-6

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Citations (150)

Simulated pre-industrial climate in Bergen Climate Model (version 2): model description and large-scale circulation features

O. H. Otter amp aring Mats Bentsen Ingo Bethke Nils Gunnar Kvamstø

Abstract. The Bergen Climate Model (BCM) is a fully-coupled atmosphere-ocean-sea-ice model that provides state-of-the-art computer simulations of the Earth's past, present, and future climate. Here, a pre-industrial multi-century simulation with an updated version of BCM is described and compared to observational data. The model is run without any form of flux adjustments and is stable for several centuries. The simulated climate reproduces the general large scale circulation in the atmosphere reasonably well, except for a positive bias in the high latitude sea level pressures distribution. Also, by introducing an updated turbulence scheme in the atmosphere model a persistent cold bias has been eliminated. For the ocean part, the model drifts in sea surface temperatures and salinities are considerably reduced compared to earlier versions of BCM. Improved conservation properties in the ocean have contributed to this. Furthermore, by choosing a reference pressure at 2000 m and including thermobaric effects in the ocean model, a more realistic meridional overturning circulation is simulated in the Atlantic Ocean. The simulated sea-ice extent in the Northern Hemisphere is in general agreement with observational data except for summer where the extent is somewhat underestimated. In the Southern Hemisphere, large negative biases are found in the simulated sea-ice extent. This is partly related to problems with the mixed layer parametrization, causing the mixed layer in the Southern Ocean to be too deep, which in turn makes it hard to maintain a realistic sea-ice cover here. However, despite some problematic issues, the pre-industrial control simulation presented here should still be appropriate for climate change studies requiring multi-century simulations.

Parametrization (atmospheric modeling)

10.5194/gmdd-2-507-2009

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Simulated North Atlantic-Nordic Seas water mass exchanges in an isopycnic coordinate OGCM

EGS - AGU - EUG Joint Assembly (2003)

Jan Even Øie Nilsen Yongqi Gao Helge Drange Tore Furevik Mats Bentsen

[1] The variability in the volume exchanges between the North Atlantic and the Nordic Seas during the last 50 years is investigated using a synoptic forced, global version of the Miami Isopycnic Coordinate Ocean Model (MICOM). The simulated volume fluxes agree with the existing observations. The net volume flux across the FaroeShetland Channel (FSC) is positively correlated with the net flux through the Denmark Strait (DS; R = 0.74 for 3 years low pass filtering), but negatively correlated with the net flux across the Iceland-Faroe Ridge (IFR; R = 0.80). For the Atlantic inflow across the FSC and IFR, the correlation is R = 0.59. For the transports through the FSC and DS, the simulation suggests that an atmospheric pattern resembling the North Atlantic Oscillation is the main driving force for the variations, involving Ekman fluxes and barotropic adjustment. The model also shows a 0.7 Sv reduction of the Atlantic inflow to the Nordic Seas since the late 50’s. INDEX TERMS: 4215 Oceanography: General: Climate and interannual variability (3309); 4255 Oceanography: General: Numerical modeling; 9315 Information Related to Geographic Region: Arctic region; 1635 Global Change: Oceans

Barotropic fluid

Inflow

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Observing and Modelling Upper Ocean Mixing by Near-Inertial Oscillations

EGU General Assembly Conference Abstracts (2016)

Helen Pillar Markus Jochum Roman Nuterman Mats Bentsen

Inertial wave

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The development of sea ice, NAO and THC in a CO2 increase ensemble with the Bergen Climate Model

EAEJA (2003)

Tore Furevik Mats Bentsen Helge Drange Nils Gunnar Kvamstø Asgeir Sorteberg

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An isopycnic ocean carbon cycle model

Karen M. Assmann Mats Bentsen Joachim Segschneider Christoph Heinze

Abstract. The carbon cycle is a major forcing component in the global climate system. Modelling studies aiming to explain recent and past climatic changes and to project future ones thus increasingly include the interaction between the physical and biogeochemical systems. Their ocean components are generally z-coordinate models that are conceptually easy to use but that employ a vertical coordinate that is alien to the real ocean structure. Here we present first results from a newly developed isopycnic carbon cycle model and demonstrate the viability of using an isopycnic physical component for this purpose. As expected, the model represents interior ocean transport of biogeochemical tracers well and produces realistic tracer distributions. Difficulties in employing a purely isopycnic coordinate lie mainly in the treatment of the surface boundary layer which is often represented by a bulk mixed layer. The most significant adjustments of the biogeochemical code for use with an isopycnic coordinate are in the representation of upper ocean biological production. We present a series of sensitivity studies exploring the effect of changes in biogeochemical and physical processes on export production and nutrient distribution. Apart from giving us pointers for further model development, they highlight the importance of preformed nutrient distributions in the Southern Ocean for global nutrient distributions. Use of a prognostic slab atmosphere allows us to assess the effect of the changes in export production on global ocean carbon uptake and atmospheric CO2 levels. Sensitivity studies show that iron limitation for biological particle production, the treatment of light penetration for biological production, and the role of diapycnal mixing result in significant changes of modelled air-sea fluxes and nutrient distributions.

Isopycnic

Biogeochemical Cycle

Mixed layer

10.5194/gmdd-2-1023-2009

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Citations (4)

Description and evaluation of NorESM1-F: a fast version of the Norwegian Earth System Model (NorESM)

Geoscientific model development (2019)

Chuncheng Guo Mats Bentsen Ingo Bethke Mehmet Ilıcak Jerry Tjiputra

Abstract. A new computationally efficient version of the Norwegian Earth System Model (NorESM) is presented. This new version (here termed NorESM1-F) runs about 2.5 times faster (e.g., 90 model years per day on current hardware) than the version that contributed to the fifth phase of the Coupled Model Intercomparison project (CMIP5), i.e., NorESM1-M, and is therefore particularly suitable for multimillennial paleoclimate and carbon cycle simulations or large ensemble simulations. The speed-up is primarily a result of using a prescribed atmosphere aerosol chemistry and a tripolar ocean–sea ice horizontal grid configuration that allows an increase of the ocean–sea ice component time steps. Ocean biogeochemistry can be activated for fully coupled and semi-coupled carbon cycle applications. This paper describes the model and evaluates its performance using observations and NorESM1-M as benchmarks. The evaluation emphasizes model stability, important large-scale features in the ocean and sea ice components, internal variability in the coupled system, and climate sensitivity. Simulation results from NorESM1-F in general agree well with observational estimates and show evident improvements over NorESM1-M, for example, in the strength of the meridional overturning circulation and sea ice simulation, both important metrics in simulating past and future climates. Whereas NorESM1-M showed a slight global cool bias in the upper oceans, NorESM1-F exhibits a global warm bias. In general, however, NorESM1-F has more similarities than dissimilarities compared to NorESM1-M, and some biases and deficiencies known in NorESM1-M remain.

Earth system science

10.5194/gmd-12-343-2019

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Citations (81)

Simulations of HAPPI (Half a degree Additional warming, Prognosis and Projected Impacts) Tier-1 experiments based on the NorESM1-HAPPI atmospheric model of the NorESM Climate modeling Consortium (NCC)

Mats Bentsen Ingo Bethke Jens Boldingh Debernard J. Fuglestvedt Christoph Heinze

Degree (music)

Tier 1 network

Climate simulation

10.26050/wdcc/happi-global-noresm1-happi

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Tracer-derived transit time of the waters in the eastern Nordic Seas

Tellus B (2005)

Yongqi Gao Helge Drange Mats Bentsen Ola M. Johannessen

The spatial-temporal distribution of the anthropogenic radionuclide 137 Cs originating from nuclear bomb testing and the Sellafield reprocessing plant in the Irish Sea is simulated using a global version of the Miami Isopycnic Coordinate Ocean Model (MICOM).The physical model has a horizontal resolution of about 40 km, and it is forced with daily atmospheric reanalysed fields for the period 1948 to 2002.A comparison of the temporal evolution of observed and simulated concentrations of 137 Cs has been conducted for the regions east of Scotland, west of central Norway and at the entrance of the Barents Sea.It follows that the annual mean 137 Cs concentration signal from the Sellafield discharge reaches the southwestern Barents Sea region in 5 yr, in accordance with available observations.To more accurately assess the age of the caesium-tagged water masses, three additional experiments were performed with an Eulerian age coupled to the evolution of the tracer concentration.It is demonstrated that the transit time depends on the duration of the tracer release history, on the dynamical ocean state and on whether the transit time is derived from the time difference between the release history and the concentration evolution downstream of the release, or as an explicit Eulerian age tracer.The Eulerian age tracer gives a transit time for a Sellafield-like discharge to reach the Barents Sea of 56 months in the 1970s, 52 months in the 1960s and 51 months in the 1980s, and that this difference is strongly governed by the ocean dynamics in the Faeroe-Scotland region.

TRACER

Transit time

10.1111/j.1600-0889.2005.00153.x

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Citations (8)

Equilibrium simulations of Marine Isotope Stage 3 climate

Climate of the past (2019)

Chuncheng Guo Kerim H. Nisancioglu Mats Bentsen Ingo Bethke Zhongshi Zhang

Abstract. An equilibrium simulation of Marine Isotope Stage 3 (MIS3) climate with boundary conditions characteristic of Greenland Interstadial 8 (GI-8; 38 kyr BP) is carried out with the Norwegian Earth System Model (NorESM). A computationally efficient configuration of the model enables long integrations at relatively high resolution, with the simulations reaching a quasi-equilibrium state after 2500 years. We assess the characteristics of the simulated large-scale atmosphere and ocean circulation, precipitation, ocean hydrography, sea ice distribution, and internal variability. The simulated MIS3 interstadial near-surface air temperature is 2.9 ∘C cooler than the pre-industrial (PI). The Atlantic meridional overturning circulation (AMOC) is deeper and intensified by ∼13 %. There is a decrease in the volume of Antarctic Bottom Water (AABW) reaching the Atlantic. At the same time, there is an increase in ventilation of the Southern Ocean, associated with a significant expansion of Antarctic sea ice and concomitant intensified brine rejection, invigorating ocean convection. In the central Arctic, sea ice is ∼2 m thicker, with an expansion of sea ice in the Nordic Seas during winter. Attempts at triggering a non-linear transition to a cold stadial climate state, by varying atmospheric CO2 concentrations and Laurentide Ice Sheet height, suggest that the simulated MIS3 interstadial state in the NorESM is relatively stable, thus underscoring the role of model dependency, and questioning the existence of unforced abrupt transitions in Greenland climate in the absence of interactive ice sheet–meltwater dynamics.

Stadial

Marine isotope stage

Meltwater

Ice-sheet model

Antarctic Bottom Water

10.5194/cp-15-1133-2019

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Citations (32)