2004 LOM Workshop Tuesday 9:00 - 9:20 a.m.
Alternative numerical scheme for the primitive equations in HYCOM
Mats Bentsen
Nansen Environmental and Remote Sensing Center
mats.bentsen@nersc.no
ABSTRACT
A numerical scheme for the inviscid, unforced primitive equations for an ocean model with isopycnic layers, will be presented. The proposed scheme uses a two-level time-stepping scheme based on a total variation diminishing second order Runge-Kutta method with modifications to the treatment of the Coriolis and Montgomery potential gradient terms for stability reasons and, in addition, a more accurate representation of the geostrophic balance. The scheme used for the transport terms in the layer equations, is based on a weighted essentially non-oscillatory scheme. A two-dimensional barotropic equation system is integrated with a time step dictated by the speed of the fast external gravity waves. These fast motions are filtered out of the layer equations which then may be integrated with a time step sufficient to resolve the much slower three-dimensional internal motions. The implementation of this split time stepping method is shown to be stable for a linearized and simplified system. Results from simulations of an idealized frontogenesis experiment and a simple wind-driven basin-scale configuration will be shown.
2004 LOM Workshop Tuesday 9:20 - 9:40 a.m.
Representing Ocean-Bottom Pressure and Sea-Surface Height in Generalized Vertical Coordinate Ocean Models
Tony Song
Jet Propulsion Laboratory
song@pacific.jpl.nasa.gov
ABSTRACT
Satellite observations of ocean-bottom pressure (OBP) and sea-surface height (SSH) are fundamentally important information about ocean dynamics. Their proper representation in current community-user models is essential for model verifications and data assimilations. The GRACE OBP represents ocean mass changes, while the TOPEX SSH gives changes of water volume. Similarly, conventional z- or Sigma-coordinate models are volume-conserving, while true isopycnal-coordinate and non-Boussinesq models are mass-conserving. In the processes of developing hybrid-coordinate and generalized coordinate models, the data representation problem has to be resolved. This talk will focus on innovative numerical methods in generalized vertical coordinate models for better representation of bottom topography and non-Boussinesq physics. Successful long-term simulations of the Pacific Ocean and ENSO events will be presented.
2004 LOM Workshop Tuesday 9:40 - 10:00 a.m.
Development of HIM into a global isopyncal model for studies of ocean circulation, biogeochemistry, and climate
Brian K. Arbic, Anand Gnanadesikan, Robert Hallberg
Program in Atmospheric and Oceanic Sciences, Princeton University
arbic@splash.princeton.edu
ABSTRACT
We have developed the Hallberg Isopycnal Model (HIM) into a realistic one degree global model useful for studies of ocean circulation, biogeochemistry, and climate. Mixed layer depths in the bulk mixed layer scheme we use are sensitive to an included parameterization for the efficiency of wind-driven mixing. The overflows are sensitive to parameterizations of the bottom boundary layer. We will present preliminary results of CFC-11, CFC-12, and perturbation anthropogenic CO2 distributions.
2004 LOM Workshop Tuesday 10:00 - 10:20 a.m.
Preliminary results for the interannual and decadal variability of a new UK coupled climate model
Alex Megann, Adrian New, Shan Sun, Rainer Bleck
Southampton Oceanography Centre
apm@soc.soton.ac.uk
ABSTRACT
The Coupled Hadley-Isopycnic Model Experiment (CHIME) comprises a new coupled model with a hybrid-coordinate ocean component (HYCOM) coupled to the Hadley Centre's HadAM3 atmospheric model. The ocean model is on a global spherical-bipolar grid with resolution 1.25 x 1.25 degrees in the spherical part of the domain, and has the Bering Strait open, while the atmosphere grid resolution is 2.5 degrees N-S and 3.75 degrees E-W. CHIME has the same atmosphere and an identical horizontal grid over most of the ocean model domain as the Hadley Centre's HadCM3 climate model but, with its isopycnal coordinate in the ocean interior, is expected to preserve water masses more faithfully while retaining adequate vertical resolution near the surface. CHIME therefore provides an excellent tool for evaluating the consequences of the choice of vertical coordinate for the ocean component of a coupled model. Preliminary results on the spinup and initial drift of the model will be presented, as well as an analysis of its interannual-decadal variability, which will be compared with corresponding results from HadCM3.
2004 LOM Workshop Tuesday 10:20 - 11:30 a.m. Poster Session
Modeling Gravity Currents in Isopycnal and Quasi-Isopycnal Ocean Circulation Models
Whit Anderson, Paul Schopf
George Mason University
datatrident@mac.com
ABSTRACT
This work investigates several modeling issues related to the representation of deep gravity currents in predominantly isopycnal ocean circulation models. We examine the role of various Richardson-number mixing schemes on the behavior of bottom currents. Previous studies have examined smoothly varying Ri-dependent schemes, and the present study re-affirms the basic results to date. But we extend these examples to consider the relative roles of bottom drag and entrainment mixing in setting the pathways and character of deep plumes. The study examines the implications of vertical resolution on the character of solutions. Richardson-number dependent mixing schemes rely fundamentally on the adequacy of vertical resolution, while global climate simulations place significant limits on the vertical resolution available for global ocean models. The implications of limited vertical resolution on such simulations is discussed. We compare the quasi-isopycnal approach to mixing and the recently developed implicit mixing techniques for isopycnal models. Both methods use the ALE technique for treating separately the processes of horizontal dynamics and vertical remapping of coordinates, but in the first case, vertical diapycnal mixing is solved after horizontal advection but before remapping, while in the latter, vertical remapping is constructed so as to include the effect of mixing.
2004 LOM Workshop Tuesday 10:20 - 11:30 a.m. Poster Session
Comparison of HYCOM with terrain-following ocean models in two idealized experiments
Valerie Garnier, Mohamed Iskandarani, Eric Chassignet, Alan Wallcraft
Rosenstiel School of Marine and Atmospheric Science, University of Miami
vgarnier@rsmas.miami.edu
ABSTRACT
HYCOM simulations are compared with those of terrain-following ocean models on simple idealized standardized tests. The emphasis is on characterizing the hybrid coordinates system in various oceanographic situations. Two tests are considered here: a gravity-adjustment and a downwelling-upwelling experiment. The gravity adjustment problem tests the tracer advections in the model while the other stresses the terrain-following aspects. For the gravity adjustment, good behavior is seen with different advection scheme although there are additional issues with conservation. The downwelling-upwelling experiment shows sensitivity to the choice of vertical coordinates.
2004 LOM Workshop Tuesday 10:20 - 11:30 a.m. Poster Session
Using Earth Rotation Data to Test Ocean Models
Richard Gross
Jet Propulsion Laboratory
Richard.Gross@jpl.nasa.gov
ABSTRACT
Angular momentum is a fundamental conserved property of dynamical systems. It is an integrated measure of mass motion and redistribution and as such can be used to diagnose the oceans' changing general circulation. Furthermore, the angular momentum of the oceans is exchanged with that of the solid Earth causing the Earth's rotation to change. In fact, a number of studies have recently shown the importance of oceanic processes in causing Earth rotation changes, particularly in exciting polar motion, which is the motion of the rotation pole with respect to the Earth's crust. Because of this demonstrated importance of oceanic processes in exciting polar motion, polar motion observations have the potential to be used as a novel means of testing ocean models. This potential is illustrated here by computing the angular momentum from runs of two different ocean models, the MOM and MICOM models. Comparing the oceanic angular momentum from these runs to polar motion excitation observations from which atmospheric effects have been removed shows that the results from MICOM are in much better agreement with the observations than are the results from MOM.
2004 LOM Workshop Tuesday 10:20 - 11:30 a.m. Poster Session
Preliminar results on the SENSIVITY OF BIOPHYSICAL MODELING TO MODEL'S VERTICAL COORDINATE REPRESENTATION
M. Olascoaga, E Chassignet, J. Kindle, A. Wallcraft
RSMAS, U. M.
jolascoa@rsmas.miami.edu
ABSTRACT
A Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) model is coupled to the Hybrid Coordinate Model (HYCOM) to make assessments of the sensitivity of plankton dynamics modeling to the choice of the model's vertical coordinate representation. An idealized two-dimensional domain (vertical cross section of a meridional channel with free surface and irregular bottom topography) is adopted for this study. The wind stress is chosen to produce upwelling (downwelling) in the west (east) channel's coast. HYCOM's flexibility to the vertical coordinate choice is exploited to perform numerical simulations using: (i) fixed z-levels, (ii) rho-coordinates (MICOM mode), (iii) following topography sigma-levels, and (iv) hybrid (z-, rho-, and sigma- coordinates) layers (standard HYCOM mode). Particular attention is paid to the effects of diapycnal mixing and mixed-layer representations on biophysical interactions modeling in the different experiments.
2004 LOM Workshop Tuesday 10:20 - 11:30 a.m. Poster Session
Estimating Salinity Profiles to Accompany XBT Data in the Gulf of Mexico and in the Gulf Stream
William Carlisle Thacker and Laurie Sindlinger
NOAA/AOML
carlisle.thacker@noaa.gov
ABSTRACT
In estimating salinity profiles that will accompany XBT data being assimilated into numerical models, the relationship between temperature and salinity for a specific region can be determined by the available CTD data. Salinity models can then be created from the CTD data at specific depths within a selected region. CTD data from the Gulf of Mexico and the Gulf Stream were used to begin exploring salinity models, but first, several procedures were necessary to give a more even sampling of the regions and to remove large outliers from the data.
2004 LOM Workshop Tuesday 10:20 - 11:30 a.m. Poster Session
A comparison of two vertical mixing schemes: Turner's vs. K-profile parameterization
Xiaobiao Xu, Eric Chassignet
RSMAS, Univ. of Miami
xbxu@rsmas.miami.edu
ABSTRACT
The ocean interior is characterized almost everywhere by very slow mixing, thus describing the diapycnal diffusion in our numerical models is straightforward. In some extreme case, for example, the gravity current generated by overflow of dense water from marginal seas, however, exhibit intense entrainment, double or even quadrupling their volume flux within a few days. Describing this vigorous entrainment is more difficult because it occurs across very sharp density gradients. And the entrainment is absolutely critical in determining the water mass properties that fill the open ocean. In isopycnal coordinate model frame, there are two options: Turner's (1986) and K-profile parameterization, both of them are Ri-dependent. In an idealized 2-D experiment, dramatically different results are found from these two schemes. Possible reasons are analyzed and short suggestion for improvement is presented.
2004 LOM Workshop Tuesday 11:30 - 11:50 a.m.
Sensitivity of climate simulations to mixing schemes in a coupled HYCOM/GISS model
Shan Sun
Goddard Institute for Space Studies, NASA
ssun@giss.nasa.gov
ABSTRACT
A new set of coupled model experiments are carried out with an improved version of the GISS AGCM, which includes a thermodynamic and dynamic ice model, and HYCOM. Two different surface layer mixing schemes, Kraus-Turner and KPP, are available. The talk focuses on the impact of different mixing parameterizations on the evolution of water masses and circulations as they affect conditions at the air-sea surface. We will also discuss some improvements in the global conservation in HYCOM.
2004 LOM Workshop Tuesday 11:50 a.m. - 12:10 p.m.
The influence of internal variability on climate projections
Helge Drange, Asgeir Sorteberg, Nils Gunnar Kvamsto, Tore Furevik
Nansen Environmental and Remote Sensing Center
helge@nersc.no
ABSTRACT
With identical greenhouse forcing climate models shows a wide range of responses both globally and regionally. This divergence from a single solution may be partly due to different model formulations and partly due to unpredictability of the climate system due to internal variability within the climate system itself. The contribution to the total model spread from each of the two uncertainties is complex and dependent on type of climate variable, the strength of the greenhouse forcing as well as the spatial and temporal scales that are investigated. In order to estimate the contribution of the spread due to internal variability an ensemble of simulations using one coupled climate model is performed. Thus the influence of intermodel differences on the spread is cancelled and it is possible to make an estimate of the influence of internal variability on the climate projections. The ensemble was carried out with the coupled Bergen Climate Model (BCM) using the atmospheric model ARPEGE with a resolution of T63 and 31 levels in the vertical and the ocean model MICOM with a resolution of 2.4 degrees along the equator and 24 vertical levels. The ensemble members have all been integrated with a 1% increase per year in CO2 content for 80 years, but started in different initial ocean and atmosphere states (taken from a control run). Our findings suggest that climate change projections over a period of less than 40-50 years will be strongly influenced by chaotic (or unpredictable) internal climate variability. Thus multi-model spread on these time-scales may partly be influenced by real model differences and partly by internal chaotic variations.
2004 LOM Workshop Tuesday 1:20 - 1:40 p.m.
On the Mechanisms of Decadal Variability of the Wind-Driven Ocean Circulation
Peter Killworth, Andrew Hogg, Jeffrey Blundell, William Dewar
Southampton Oceanography Centre
p.killworth@soc.soton.ac.uk
ABSTRACT
Eddy resolving simulations of wind driven circulation in a large ocean basin are presented. A series of numerical experiments are used to demonstrate that the mean state and variability of the circulation is dependent upon the strength of ocean eddies, which in turn are controlled by parameters such as viscosity and bottom drag. In particular, strong modes of low-frequency variability arise in many parameter regimes, and these modes depend upon the presence of ocean eddies in the simulation. The dependence upon eddies may be due to either an eddy--mean flow feedback loop, or else may occur because of oscillations in the mean flow which contains strong nonlinear features due to the cumulative effect of the eddy field. Both of these possibilities are explored. In addition it is shown (using a coupled version of the model) that this intrinsic ocean variability may contribute to midlatitude climate variability.
2004 LOM Workshop Tuesday 1:40 - 2:00 p.m.
Origins and dynamics of the 90-day and 30-60 day variations in the equatorial Indian Ocean
Weiqing Han
University of Colorado
whan@enso.colorado.edu
ABSTRACT
A thorough investigation of the origins and dynamics for the surface and subsurface zonal currents at 20--90 day period in the equatorial Indian Ocean is conducted using an ocean general circulation model (OGCM). To help understand the wind-driven equatorial wave dynamics that occur in the OGCM, a linear continuously stratified ocean model (LM) is also used. Solutions are found in a realistic tropical Indian Ocean basin, and they are forced by NCEP 3-day and monthly forcing fields, together with CMAP pentad and monthly precipitation, for the period of 1988--2001. At both the surface and subsurface, the OGCM solution forced by the 3-day mean fields shows a dominant spectral peak of zonal currents at 90-day period and secondary peaks at 30--60 days, with the 90-day maxima shifting westward as depth increases. These features also appear in the LM solution, suggesting that the wind-driven equatorial wave dynamics play a deterministic role in causing the intraseasonal currents. The dominant 90-day peak is observed by the TOPEX/POSEIDON altimetry data throughout the equatorial Indian Ocean, and is detected by current measurement near the Indonesian seas. The 90-day TOPEX/POSEIDON sea level anomaly and the OGCM surface current evidently show the equatorial Kelvin and the first meridional mode Rossby wave structure, demonstrating that the 90-day oscillation in the equatorial Indian Ocean results from the equatorial waves in responding to the basin scale, 90-day wind forcing. Although zonal currents peak at 90 days, zonal winds peak at 30-60 day period. The skew of frequency between forcing and response results primarily from two causes, consistent with the author's 4.5-layer model study. First, the lower frequency, larger scale Kelvin and Rossby waves at the 90-day period are more efficiently excited by the large scale winds than the higher frequency, shorter wavelength 30--60 day waves. Second, Rossby waves reflected from the eastern ocean boundary significantly enhance the interior response, because the second baroclinic mode resonates with the 90-day wind. The Maldives Islands in the central equatorial basin weaken the resonance somewhat. Although most energy is surface trapped due to mixing, pycnocline reflection, and critical layer absorbtion, there is a fair amount of energy penetrates through the pycnocline down to the deep ocean. A clear upward phase propagation presents in the 90-day zonal flow, indicating that energy is propagating down. Energy of the 90-day Rossby waves excited by the wind maxima near 70E--80E propagates down along the WKB ray path, which appears to explain the westward migration of the 90-day variance maxima. These maxima are significantly enhanced by the reflected Rossby waves at all depths owing to the resonance effect. At 30--60 day period, zonal currents also result largely from intraseasonal wind forcing. At the surface and in the basin interior, the 30--60 day zonal currents are caused by directly forced Rossby and Kelvin waves, and effects of reflected Rossby waves are negligible. As depth increases, however, reflected Rossby waves become more important. This is because the WKB ray paths for the 30--60 day Rossby waves are two to three times steeper than the 90-day ones, energy associated with the reflected Rossby waves penetrate down to the deep ocean efficiently and thus has little effects at the surface. Although intraseasonal wind forcing is important, oceanic instabilities are not negligible near the western boundary and in the central basin south of Sri Lanka near 5N.
2004 LOM Workshop Tuesday 2:00 - 2:20 p.m.
Coupled Modes of variability in the South Atlantic. A comparison of model results with observations
Edmo Campos, Roberto DeAlmeida, Reindert Haarsma, Rainer Bleck and Carlos Lentini
Instituto Oceanografico da Universidade de Sao Paulo
edmo@io.usp.br
ABSTRACT
Coupled modes of variability in the South Atlantic were investigated with the output of the MICOM-CCM3 ocean-atmosphere model, run at the Los Alamos National Laboratory. The main objective was to compare the model patterns of variability, from interannual to multidecadal time-scales, with results of similar analyses with the NCEP data set. Using EOFs and Maximum Covariance Analysis (MCA) between SST and MSLP with zero lag, we found dipolar modes of SST variability very similar to those reported in the scientific literature in recent years. Spectral analysis of the dipole-like mode of SST variability in the model output shows two significative time-scales: one at 2.5 years and the othr at 27 years. The interannual time-scale is correlated with the ENSO signal while the multidecadal variability seems to be related to the Atlantic Meridional Overturning Circulation. Similarly to a previous study with NCEP data, lead-lag MCA between anomalous SST and atmospheric variables, with the model output, indicate the existence of two modes of variability of the atmospheric South Atlantic Convergence Zone (SACZ). One of these modes is a result of remote forcing while the other is a local response to the oceanic forcing. The differences between the two analyses are due to the different climatological states of the data and the model output: there is an excessive southward displacement of the Austral Summer ITCZ in the model result.
2004 LOM Workshop Tuesday 2:20 - 2:40 p.m.
Impact of atmospheric intraseasonal variability in the Indian Ocean: low-frequency rectification in equatorial surface current and transport
Weiqing Han, Peter Webster, Roger Lukas, Peter Hacker, and Aixue Hu
Univeristy of Colorado at Boulder
whan@enso.colorado.edu
ABSTRACT
An ocean general circulation model, the HYbrid Coordinate Ocean Model (HYCOM), is used to investigate the low-frequency (period longer than 90 days) rectification of atmospheric intraseasonal variability (10--90 day periods) in zonal surface current and transport of the equatorial Indian Ocean. A hierarchy of HYCOM solutions are found in an actual tropical Indian Ocean basin for the period of 1988--2001. To help identify nonlinear processes, a linear continuously stratified model is also used. To isolate the contribution from various nonlinear processes, a 4.5-layer intermediate ocean model is applied. Results from HYCOM solutions suggest that intraseasonal atmospheric forcing acts to weaken the equatorial zonal surface currents. Amplitudes of the spring and fall eastward surface jets, the Wyrtki Jets (WJs), and the westward surface current during January--March are reduced by as much as 15-25 cm/s by intraseasonal atmospheric forcing. Important processes that cause the rectification are: asymmetric response of mixed layer depth to easterly and westerly winds, entrainment, and upwelling. During an intraseasonal event, westerly wind deepens whereas easterly wind shoals the surface mixed layer. A net, westward current is generated over an event mean because easterly wind acts onto a thinner surface mixed layer whereas westerly wind acts onto a thicker one. Meanwhile, the strong, episodical westerly winds enhance the entrainment of the slower subsurface water into the surface mixed layer, also tend to weaken the WJs. In contrast, during January--March when the seasonal winds are equatorial easterlies, surface currents are westward, equatorial undercurrents (EUC) develop, and mixed layers are thin. The rectified surface currents are eastward, which reduce the westward surface flow. This eastward rectification results largely from the vertical advection and entrainment of the EUC. In the layers above the thermocline, the rectified zonal transports are westward when the WJs are significantly weakened. The total rectified zonal transports over the entire water column, however, are eastward with an amplitude of 3-15 Sv. This is because westerly winds generate equatorial downwelling, advecting the surface eastward momentum downward and giving an eastward subsurface current. Easterly winds cause equatorial upwelling and produce an eastward pressure gradient force that drives an eastward subsurface current. This eastward subsurface current is advected upward due to upwelling. The mean effect over an intraseasonal event is to create an eastward transport in the water column. Results from this paper have important implication for understanding climate variability because modification of WJs strength and transport can affect the SST and heat storage in the eastern Indian Ocean warm pool region.
2004 LOM Workshop Tuesday 2:40 - 3:00 p.m.
A new model of buoyant plumes
VMCanuto, MSDubovikov and NLTausnev
NASA,- Columbia University, NY, NY
vcanuto@giss.nasa.gov
ABSTRACT
Buoyant Plumes play a key role in describing Deep Convection in the ocean. The canonical plume model of Taylor and Turner (TTM) cannot however be directly used since it was developed for a solitary plume whose cross section is much less than that of the environment. In the ocean case, stable stratification slows down the vertical plume velocity and since entrainment causes the mass flux to increase, the plume cross section increases toward unity thus making the TTM model inapplicable. A new plume model, free of this limitation, has been developed and tested against Deep Convectiion data of Schott et al.(1996). The theoretical basis of the model and the model predictions will be discussed.
2004 LOM Workshop Tuesday 3:20 - 3:40 p.m.
Characteristics of ventilation in ocean models
Kelvin Richards
IPRC/SOEST, University of Hawaii
rkelvin@hawaii.edu
ABSTRACT
The characteristics of ventilation of the thermocline is examined in models of the North Pacific and Atlantic oceans. The OGCM used in this study is MICOM, which maps comfortably onto conceptual models of the ventilation process. Both the pattern and rate of ventilation is found to be strongly dependent on the level of thickness diffusion in the model, with the sensitivity of the Atlantic being more than that of the Pacific. The results highlight the need for more consideration to be paid to the specification of lateral mixing in models used in climate studies. Comparison is made with the observed distribution of CFCs, demonstrating the difficulty in using such data to discriminate between ocean models.
2004 LOM Workshop Tuesday 3:40 - 4:00 p.m.
Investigation of the Temporal and Spatial Variability of the North Atlantic Subtropical Mode Water Using Float Data and Numerical Model Results
Ge Peng, Eric Chassignet, Young-Oh Kwon, Stephen Riser
RSMAS/University of Miami
gpeng@rsmas.miami.edu
ABSTRACT
The properties of the North Atlantic Subtropical Mode Water (STMW), i.e., the 18-degree water (EDW), are calculated with float profiling observational data and ocean circulation model results. The basic characteristics of STMW are well documented in the literature from one time hydrographic sections or long term measurements at one location. Since the summer of 1997, up to 71 profiling floats were launched in the Western Subtropical North Atlantic region. The broad coverage in both time and space of the float profiles enables us to investigate the spatial and temporal variability of the STMW. In this study, we evaluate the performance of a North Atlantic numerical simulation against these float data, using the Miami Isopycnic Coordinate Ocean Model (MICOM). The good agreement between the two allows us to discuss the sensitivities of the float-derived results to observational sampling area and data coverage. Float-derived STMW properties are found to display more spatial variation when compared to the model-derived ones, even with the float profiles binned and mapped onto the model grid. Most variability of the model-derived STMW properties occurs at the northeast portion of the STMW domain and the least in the southeast. The spatial and temporal variability of model subduction rates and ventilation patterns will be described. The time series of domain averaged STMW temperature in both the model and observations do not show statistically significant seasonal and interannual variabilities while that of STMW volume displays a primary peak in the spring (March to May) each year and a secondary peak at October. Multi-year and decadal variabilities of the North Atlantic STMW properties (temperature, volume, subduction rate, etc.), and their relationship to the NAO will also be discussed using the model results.
2004 LOM Workshop Tuesday 4:00 - 4:20 p.m.
Micom as the ocean component of a regional coupled climate model
Jens Debernard
Norwegian Meteorological Institute
jens.debernard@met.no
ABSTRACT
Regional atmospheric climate models are popular tools used to refine climate change scenarios from coarse resolution global climate models to asses possible climate changes at regional scales. However, in some regions these models may experience unphysical behavior due to the lack of strong feedback mechanisms caused by sea ice. In the northernmost parts of Europe, this may be an important problem. Therefore, we develop a regional coupled climate model for the Arctic. The coupled system consist of a regional atmosphere model, an ice model that also acts at the coupler, and our version of the ocean model MICOM. The talk will focus on the strategy and methodology for the coupling together with results from coupled ice-ocean simulations for a domain covering the Atlantic and Arctic oceans.
2004 LOM Workshop Tuesday 4:20 - 4:40 p.m.
Modelling the ocean circulation and the transformation of water masses over the Ross Sea Continental Shelf, including the Ross Ice-Shelf Cavity
Miguel Angel Morales Maqueda, David Holland
Courant Institute of Mathematical Sciences of New York University, New York, NY
maqueda@cims.nyu.edu
ABSTRACT
The isopycnic coordinate model MICOM is employed here to model the ocean circulation over the continental-shelf region of the Ross Sea and underneath the Ross Ice Shelf.Our goal is to determine the impact of ocean-ice shelf interactions on the transformation of water masses in the region.To avoid having to deal with problematic boundary conditions on the eastern Ross Sea, the model domain encompasses as well the continental-shelf areas all the way to the Antarctic Peninsula.Our model simulations suggest that year-to-year variability in the westward advection of relatively fresh waters from the Amundsen and Bellinghausen Seas into the Ross Sea has the potential to strongly affect the circulation and water properties both in the Ross Sea proper and beneath the Ross Ice-Shelf.
2004 LOM Workshop Tuesday 4:40 - 5:00 p.m.
Ice Shelf - Ocean Model Intercomparison Project
David Holland, Miguel Angel Morales Maqueda
New York University
holland@cims.nyu.edu
ABSTRACT
The Ice Shelf - Ocean Model Intercomparison Project (ISOMIP) is currently being proposed as an open, international effort to identify systematic errors in sub-ice shelf cavity ocean models. In this presentation, the first intercomparison results from the project are presented and discussed, with a focus on the results from the isopycnic model (i.e., MICOM) used in the study. The presentation also includes a discussion of modifications to the surface boundary conditions for salt flux in isopycnic models, whereby the usual virtual salt flux is replaced by a natural boundary condition, involving mass flux arising from the melting of the overlying ice shelf. The sensitivity of the modeled ocean circulation to this change in surface boundary condition is presented. Further information on the overall project may be found at URL http://fish.cims.nyu.edu/project_oisi/isomip/overview.html.