1.1 Major Goals of the Project

ACCIMA Annual Report 2013

1Accomplishments

1.1 major goals of the project

[Drag and Drop text]

The Atmosphere-Ocean Coupling Causing Ice Shelf Melt in Antarctica (ACCIMA) collaborative project combines teams of researchers at The Ohio State University (OSU), New York University (NYU) and Old Dominion University (ODU) to model the multi-disciplinary processes impacting the Antarctic Ice Sheet. The major goal of this project is to understand the various processes in the atmosphere, ocean, cryosphere and on land that influence the delivery of heat to the Antarctic Ice Sheet, which then causes the ice sheet to melt and raise global sea level. To understand these processes, we will create a coupled model of the polar Southern Hemisphere with high enough horizontal resolution to represent mesoscale dynamics in each of these component systems.

The first step toward this goal is to create individual versions of the atmosphere (Polar-WRF), ocean (ROMS, POP2), sea-ice (CICE, ROMS), land (CLM) and ice shelf (ROMS) on a common grid with a spacing that ranges from 30 to 10 km. These component models are run with external forcing created either by the other models or by various analysis products.The purpose of these experiments is to specify the various constants and processes so that the models will realistically represent the dynamics of the polar Southern Hemisphere.

The second step toward the major goal is to allow some of the individual models to be coupled so they can adjust freely to the changes in the other model states. We will use the software set up by the Community Earth System Model (CESM) and NCAR which provides a coupling environment for the individual models above. At the moment, different versions of CESM softwareallow different coupling options. WRF is not yet part of the latestrelease (cesm1.1.1) although it is part of an earlier release (cesm1.0.4). Workis proceeding to make ROMS part of CESM, but no software has beenreleased to date.

The third step is to couple all models to allow free interaction and influenceamong them. This will require a new release of CESM (anticipatedsoon).

The final step is to reduce the model grid to 10 km for the coupled systemto allow the ocean to be almost eddy-resolving and for the atmosphere to feelthe effects of these small scales in the ocean as well as allow the atmosphereto react to topographic variations on the land and thus create katabatic andbarrier winds.

1.2Accomplishments

[The Section will be included in the pdf file submitted as supplementary information]

1.2.1Major Activities

WRF– Benchmarking the performance of Polar WRF in the Antarctic was completed (Bromwich et al. 2013). Simulations with Polar WRF on a 30-km version of the ACCIMA grid were performed to generate high resolution atmospheric forcing for the ocean models.

CLM– Simulations with CLM on the 20 km grid to get a dynamicallyadjusted base state.

ROMS– Simulations with ROMS on the 10 km grid forced by ERA interimmeteorology and ECCO2 oceanat the boundaries to get ocean, sea ice andice shelf processes properlyrepresented.

POP2– Simulations with POP2 on the 20 km grid forced by the CommonOcean-ice Reference Experiments Datasets version 2 (COREv2, Large andYeager 2008) which is composed of 6-hour NCEP/NCAR reanalysis on T62grid for surface air wind, temperature, and specific humidity; monthly precipitationfrom a blend of GPCP (Huffman et al. 1997), CMAP (Xie and

Arkin 1997), and Serreze products; and daily radiation is from GISS. Lateral boundary conditions are specified from ECCO2 to get a dynamically adjusted initial ocean state and to properly specify various ocean model parameters.

POP2+CICE– Simulations with coupled POP2 and CICE on the 20 kmgrid forced by COREv2 (described above) to evaluate the interaction betweenthese models.

Yellowstone– Using the newly commissioned UCAR computer (yellowstone)for test simulations and to set up the production calculations thatwill involve all of the coupled models.

1.2.2Specific objectives

WRF– Simulations with the Polar version of WRF (Polar WRF) were done to determine the optimum strategy for modeling on the ACCIMA grid. Using this strategy, Polar WRF was run at 30 km and 3-h output frequency for 2010 with specified sea surface temperatures and sea ice conditions and lateral boundary forcing from the ERA-Interim global reanalysis. The output data set will be used to force the ocean models.

CLM– Create an adjusted state for the land model forced by the seasonallyvarying surface fluxes. Simulations have been run for 80 years toallow the deeper ice layers to equilibrate to the seasonally varying surfaceheat fluxes.

ROMS– Create an eddy-permitting ocean/sea-ice/ice-shelf model simulationdriven by surface winds and air temperature from ERA-interim. Thesesimulations have been done on the 10 km grid for the Southern Ocean.

POP2– Create an ocean only (POP2) and a coupled ocean/sea-ice simulation(POP2-CICE) on the 20 km grid forced by NCEP-reanalysis meteorology.

WRF-CLM– Create a coupled atmosphere-land simulation on the 20-km grid that is driven by the ERA-Interim global reanalysis using spectral nudging and specified ocean conditions. This work is ongoing.

1.2.3Significant results

WRF–Extensive experimentation was done with Polar WRF on the ACCIMA grid at 30 km to find the optimal integration strategy. Figure 1 shows the integration domain along with the selected physics options used in WRF. The 30-km domain was nested inside a coarser outer domain (90 km) to provide smooth lateral boundary conditions for the inner domain (30 km). The ERA-Interim global reanalysis provided the lateral boundary conditions for the coarse domain. To prevent WRF model drift during extended integrations of up to several months in duration spectral nudging to ERA-Interim was used in the inner domain. It was found that nudging of waves 1-7 at upper model levels provided the most stable and realistic solution while minimizing the nudging needed so that smaller scale simulation features can realistically develop.

Using this integration strategy, Polar WRF was run for 2010 using a 3-h output frequency. The benefit of the higher resolution provided by Polar WRF (30 km versus ~ 80 km for ERA-Interim) is demonstrated by Figure 2 that shows the simulated total precipitation for January 2010 for both ERA-Interim (left) and Polar WRF (right). The orographic precipitation upwind of the South American Andes (top left) is much more pronounced in Polar WRF as is the downwind precipitation shadow in comparison to ERA-Interim. Another example is provided by the Polar WRF precipitation along the Queen Maud Land coast of Antarctica (top) where the windward facing slopes show precipitation maxima whereas these features are weakly represented or absent from ERA-Interim. Polar WRF resolves mesoscale lows that are not present in ERA-Interim and the surface winds over the Antarctic ice sheet, as expected, have a lot more spatial structure in Polar WRF (figures not shown).

CLM– The land model has stabilized to a repeating seasonal cycle providing initial conditions for the coupled simulations. CLM represents the Antarctic ice sheet with about 2 m of snow (about 1 m water equivalent depth) on top of solid ice. Using 2003 forcing conditions every 3 hrs (Qian et al 2006), it is seen that the surface temperature on top of the snow layer, which can communicate to the atmosphere, adjusts very rapidly to the forcing. At deeper CLM model layers down to 35 m deep in the Antarctic ice the annual temperature cycle is smalland decades are required for equilibrium with the surface forcing. After 80 yrs of simulation the 35 m ice temperature becomes similar to the annual mean surface air temperature.

ROMS–The ROMS based ocean/sea-ice simulation creates realistic seaice concentration with a seasonal cycle that matches the observed cycle forthe Southern Ocean (Fig.3A). In addition, the volume transport at DrakePassage (Fig.3B) is 139 ± 10 Sv which is close to the observed 134 ± 11 Sv(Cunningham et al. 2003). Finally, the basal melt under the three largest iceshelves (Fig 3C) has a stable seasonal pattern with little drift and compares reasonably with observations for the Ross (0.16 m/y vsobs of 0.12 to 0.22; Shabtaie et al. 1987, Lingle et al. 1991, Jacobs et al. 1992, Loose et al. 2009), Filchner-Ronne (0.20 m/yr vsobs of 0.24-0.44; Nicholls et al. 2003) and Amery (1.1 m/yr vsobs of 0.5-1.1; Galton-Fenzi et al. 2012).

POP2– The POP2 ocean-only simulation on the 20 km grid behaves reasonably.The transport at Drake Passage is above the observed range withvalues varying between 145 and 170 Sv (Fig.4). Over time, there is someerosion of the internal temperature and salinity structure which indicatesexcessive vertical mixing driven by vertical convection during the winter.

POP2+CICE– The coupled POP2-CICE simulations have been run overseveral years. The model develops low sea ice concentration in the winter(Fig.5) and near-freezing water over much of the ocean south of the ACC(Fig.6). The excess vertical convection in the winter is due to somewhatweak near-surface stratification. Experiments are underway to adjust initial conditions to avoid this runaway convection and venting of deep heat from the ocean.

1.2.4Key outcomes

• Individual component models have been run on the regional 10 km to30 km grids over the polar Southern Hemisphere. The atmosphere (Polar WRF), land (CLM)and ocean (ROMS) produce realistic simulations for current conditionscompared to present day observations.

• The ocean/sea-ice/ice-shelf model based on ROMS has a very goodability to simulate the transport at Drake Passage, the global sea icearea, and the ability to calculate basal melt in response to these processes.We are currently using this model to assess the impact of changingresolution in the atmospheric model on the resulting ocean circulation(from ERA-interim to 30 km Polar-WRF). We will be able to usethis model directly when the coupling software is released with ROMSas a component model in CESM. ROMS also acts as a good test modelto help adjust processes in POP2 to get realistic ocean simulations(from ERA-interim to 30 km Polar-WRF).

• Pairwise coupling of several models (CLM-WRF, POP2-CICE) havebeen completed or nearing completion. The ocean model displays a runaway convection; proceduresto resolve these difficulties are underway.

1.2.5References:

Bromwich, D. H., F. O. Otieno, K. M. Hines, K. W. Manning, and E. Shilo, 2013:.Comprehensive evaluation of polar weather research and forecasting performance in the Antarctic. J. Geophys. Res., 118, 274-292, doi: 10.1029/2012JD018139.

Cunningham, S.A., S.G. Alderson, B.A. King, and M.A. Brandon, 2003.Transport and variability of the Antarctic Circumpolar Current in DrakePassage.J. Geophys. Res., 108, 8084.doi: 10.1029/2001JC001147.

Galton-Fenzi, B. K., J. R. Hunter, R. Coleman, S. J. Marsland, and R.C. Warner, 2012. Modeling the basal melting and marine ice accretionof the Amery Ice Shelf, J. Geophys. Res., 117, C09031,doi:10.1029/2012JC008214.

Huffman, G. J., and Coauthors, 1997. The Global Precipitation ClimatologyProject (GPCP) Combined Precipitation Dataset. Bull. Amer. Meteor. Soc., 78, 5-20.

Jacobs, S.S., H.H. Hellmer, C.S.M. Doake, A. Jenkins, and R.M. Frolich, 1992.Melting of ice shelves and the mass balance of Antarctica.J. Glaciology,38, 375-387.

Large, W., and S. Yeager, 2008.The global climatology of an interannuallyvarying air-sea flux data set.Climate Dynam.,33, 341-364, doi:10.1007/s00382-008-0441-3.

Lingle, C.S., D.H. Schilling, J.L. Fastook, W.S.B. Paterson, and T.H. Brown,1991.A flow band model of the Ross Ice Shelf, Antarctica responseto CO2-induced climatic warming. J. Geophys. Res., 96, 6849-6871.

Loose, B., P. Schlosser, W.M. Smethie, S. Jacobs, 2009. An optimized estimateof glacial melt from the Ross Ice Shelf using noble gases, stableisotopes, and CFC transient tracers.J. Geophys. Res.,114, C08007.doi: 10.1029/2008JC005048.

Nicholls, K. W., L. Padman, M. Schröder, R. A. Woodgate, A. Jenkins, and S. Østerhus, 2003. Water mass modification over the continental shelf north of Ronne Ice Shelf, Antarctica, J. Geophys. Res., 108, 3260, doi:10.1029/2002JC001713, C8.

Qian, T., A. Dai, K.E. Trenberth, and K.W. Oleson, 2006.Simulation of global land surface conditions from 1948-2004. Part I: Forcing data and evaluation. J. Hydrometeorology, 7, 953-975.

Shabtaie, S., and C.R. Bentley, 1987. West Antarctic ice streams draining into the Ross Ice Shelf: Configuration and mass balance. J. Geophys. Res., 92, 1311-1336.

Xie, P., and P. A. Arkin, 1997. Global Precipitation: A 17-Year Monthly Analysis Based on Gauge Observations, Satellite Estimates, and Numerical Model Outputs. Bull. Amer. Meteor. Soc., 78, 2539-2558.

1.3Training and professional development

[Drag and Drop text]

1.3.1Postdocs

C. Yoo attended three workshops: the EaSM-PI meeting at NSF headquarters in Washington DC in July 2012, Southern Ocean Observing System (SOOS) workshop at Hobart, Australia in October 2012, and WCRP special workshop on Ozone and SH climate at Buenos Aires, Argentina in February 2013.

1.3.2Grad students

J. Nicolas attended the WCRP special workshop on Ozone and SH climate at Buenos Aires, Argentina in February 2013 and presented a poster.

1.3.3Undergrad students

[none to report]

1.4Results to communities of interest

This is achieved through extensive participation in conferences and workshops where the ACCIMA project is discussed/presented.

1.5 Plans for next time interval to accomplish goals

The major activity is for the individual groups to finish calibrating the individualmodels and to run simulations with coupled models.

Collaboration of the three groups is maintained with a conference call at 2 week intervals.

The next annual project meeting will be held at Ohio State once the coupled model is fully operational; this likely will occur in fall 2013.

We will stay in touch with CESM software development to determine when new models are included in the coupling framework and are released to research groups for their use.

1.6Supporting pdf files

[include results from Section 1.2 above in the pdf file.]

2 Products

2.1Publications

2.1.1 journal publications

Bromwich, D. H., F. O. Otieno, K. M. Hines, K. W. Manning, and E. Shilo, 2013: Comprehensive evaluation of polar weather research and forecasting performance in the Antarctic. J. Geophys. Res., 118, 274-292, doi: 10.1029/2012JD018139.

Nadeau, L.-P., D.N. Straub, and D.M. Holland, 2013: Comparing idealized and complex topographies in quasigeostrophic simulations of an Antarctic Circumpolar Current. J. Phys. Oceanogr., in press.

2.1.2books, non-periodical

[None to report]

2.1.3 conference papers, presentation abstracts

EASM project PI meeting, Washington DC, July 8 to July 11, 2012. C. Yoo presented a poster How important is atmosphere-ocean coupling on fine scales for communicating the large scale ozone signature to Antarctica? (attending: Klinck, Hines, Yoo)

SCAR Open Science meeting, Portland, Oregon (attending: Bromwich)

FRISP/WAIS meeting (attending: Dinniman)

WGOMD/SOP Workshop on Sea Level Rise, Ocean/Ice Shelf Interaction and Ice Sheets, Hobart, Tasmania, Australia, Feb 18 - Feb 20, 2013 (attending: Holland)

Southern Ocean Observing System (SOOS) workshop at Hobart, Australia in October 2012 (attending: Yoo)

WCRP special workshop on Ozone and SH climate at Buenos Aires, Argentinain February 2013 (attending: Yoo and Nicolas)

Posters presented:

Bromwich, D.H., L.-S.Bai, M. Dinniman, E. Gerber, K. Hines, D. Holland, J. Klinck, J. Nicholas and C. Yoo. The ACCIMA Project - Coupled Modeling of the High Southern Latitudes. 26thForum for Research into Ice Shelf ProcessesWorkshop, Stockholm, Sweden, 12-14 June 2012.

Hines, K.M., D.H. Bromwich,L.-S.Bai, J.P. Nicolas, D.M. Holland, J.M. Klinck, M. Dinniman, C. Yoo, and E.P. Gerber. The ACCIMA Project – Coupled Modeling of the High Southern Latitudes. 17th Annual Community Earth System Model (CESM) Workshop, Breckenridge, CO, 18-21 June 2012.

Bromwich, D.H., and K.M. Hines.ACCIMA. XXXII SCAR Open Science Conf., Portland, OR, 16-19 July 2012.

Bromwich, D. H., L.-S.Bai, M. Dinniman, E. Gerber, K. Hines,D. Holland, J. Klinck, J. Nicolas, and C. Yoo, 2013: How important is atmosphere-ocean coupling on fine scales forcommunicating the large scale ozone signature to Antarctica?World Climate Research Programme (WCRP)Special Workshop on Climatic of Ozone Depletion in the Southern Hemisphere, Buenos Aires, Argentina, 25February-1 March 2013.
Nicolas, J. P., D. H. Bromwich, and A. J. Monaghan, 2013: West Antarctic temperatures and atmospheric circulation changes since the International Geophysical Year. World Climate Research Programme (WCRP)Special Workshop on Climatic of Ozone Depletion in the Southern Hemisphere, Buenos Aires, Argentina, 25February-1 March 2013.

2.2Technologies or techniques

[None to report]

2.3Inventions and patents

[None to report]

2.4Websites

[None to report]

Project Website for the ACCIMA project:

(password protected)

Website for Polar WRF:

2.5Other products

Polar WRF 3.4.1 – polar-optimized supplement to the widely-used Weather Research and Forecasting Model

2.6Supporting pdf files

[addpdf file]

3 Participants and collaborators

3.1Worked on project

[Individual information is added on the web site]

3.1.1Senior Personnel

[add contribution to the project on local report]

• L.-S. Baihas worked on running Polar WRF to simulate 1 year over the ACCIMA Antarctic grid.

• D. Bromwichis the overall project leader and has organized communication between groups along with publications, reports, and bi-weekly conference calls.

• M. Dinnimanis responsible for developing and configuring the Southern Ocean model with ROMS. This model includes sea ice and ice shelves. In addition, he is using the ROMS model to help calibrate the POP2 model so that it will provide realistic simulations of the Southern Ocean.