cesm cross working group meeting navigating the new arctic ... · benchmarking models against field...
TRANSCRIPT
This material is based upon work supported by the National Center for Atmospheric Research, which is a major facility sponsored by the National Science Foundation under Cooperative Agreement No. 1852977.
CESM Cross Working group meeting –Navigating the New Arctic with CESM
June 19, 2019
Andrew Gettelman, Marika Holland, Alice DuVivier
CESM Directions
Where are we now in the Arctic? Where are we going?
• CAM6 = Much better polar clouds
• Improved TOA and surface fluxes
TOA Cloud Radiative Effect
Atmosphere: Where we are
CAM6
CAM5
CAM6
Obs (ARM)
CESM2-CAM6: Better Arctic Clouds
• Lots of work on S. Ocean clouds with new data. – Next few years will have more Arctic data
• Ice formation important in S. Ocean. Critical in Arctic– Ice Nucleating Particles (INP) & Riming are key processes
• Working on improving cloud microphysics and INP
ObsExample: Simulating Observed Size Distributions
in CESM2 over the S. Ocean from SOCRATES in
2018 (Hobart & South)
Atmosphere: Where we are going
• New Capabilities with SE dynamical core to run refined mesh at high resolution over different regions: e.g. Arctic
• Couple to Land, Land Ice at high resolution.
• What ocean/sea ice resolution to build?
• Could do this with CESM2.1.1
Sample: 25km mesh over the Arctic.• 25km, could do a century • 14km, decades • 7km, seasons to years
Atmosphere: Where we are going (High Res)
From Holland, Bailey, and DuVivier
1979-2014 average
CAM6
WACCM6
Obs
CAM6
WACCM6
Sea Ice: Where we are
CESM2:
• 8 sea ice, 3 snow vertical levels(doubled/tripled respectively)
• Mushy layer thermodynamics
• Mean climate, trends are pretty good
• Interesting differences due to atmosphere.
Sea Ice: Where we are
• In development:
– Water isotopes
– Incorporating CICE6 into CESM3 – the column physics has been separated from the dynamics.
– Floe size distribution –UW and New Zealand
– Albedo/snow – using upcoming MOSAiCobservations
Sea Ice: Where we are going
• Development wish list:
– Satellite simulators
– Dynamics
– Biogeochemistry thru column
– Snow model improvements
– Data assimilation
– “Arctic CESM” Configuration
– Benchmarking product
Permafrost and cold region research priorities
David LawrenceClimate and Global Dynamics LaboratoryWith contributions from Sean Swenson,
Christina Schaedel, and Charlie Koven
Benchmarking models against field experiments
Growing season gross primary productivity (GPP)
Schaedel et al, 2018
Artificial warming
Snow fence experiment
Abrupt permafrost thaw
20% of permafrost domain has high ice content and
is potentially subject to abrupt thaw and rapid
increases in CO2 and CH4 emissions
Thermokarst lakes
Hillslope failure
Simple model for abrupt thaw suggests that
it could amplify permafrost climate-carbon
feedback by up to a factor of 2 (Turetsky et
al., Nature, 2019)
Yuri Kozyrev/NOOR/eyevine
Steven Kazlowski/NPL
Ground heat flux
Sub-surface lateral water flux
Lateral diffusive heat flux
Frozen soil
Ice lens
N
Saturated soil
Snow
Water
track
flow
Ground heat flux
Sub-surface lateral water flux
Lateral diffusive heat flux
Frozen soil
Ice lens
Saturated soil
Snow
Upland system
after ice melt
Water
track
flow
after ice melt
Ground heat flux
Sub-surface lateral water flux
Lateral diffusive heat flux
Frozen soil
Ice lens
Saturated soil
Snow
after ice melt
Water
track
flow
after ice melt
Lowland system
Ground heat flux
Sub-surface lateral water flux
Lateral diffusive heat flux
Frozen soil
Ice lens
Saturated soil
Snow
Impacts of abrupt
thaw on infrastructure Water
track
flow
(b) summer (lowland system)
after ice melt
Land Model: development priorities
• Blowing snow
• Subsidence and lateral water distribution
• Abrupt thaw processes (thermokarst)
• Carbon, nutrient, and sediment transport via rivers
• River ice
• Arctic vegetation (moss, wetland vegetation)
Community Ice Sheet Model (CISM) v2.1, released with CESM2
• Parallel, higher-order ice sheet dynamics
• Improved physics for basal sliding, iceberg calving, sub-shelf melting
• Focus on Greenland
New land-ice capabilities in CESM2
• Improved glacier surface physics in CLM
• Support for two-way coupling between the Greenland ice sheet and the
land and atmosphere (with dynamic landunits)
Land Ice: model development
Interactive Greenland ice sheet
• JG/BG spinup: Efficient method of spinning up Greenland to equilibrium with preindustrial climate:
~300 yr CAM, 1 kyr POP, 10 kyr CISM
• ISMIP6 coupled experiments: piControl, 1pctCO2, historical, ssp5-85; interactive Greenland ice
sheet. Under way.
• Transient Last Interglacial: 127 – 121 ka, with 10x acceleration of ice sheet and orbitals (Aleah
Sommers). Coming soon.
Interactive Laurentide ice sheet
• Last Deglaciation in N. Hemisphere: Long transient simulation including new POP–CISM coupling
(Sarah Bradley, Michele Petrini). Test runs under way.
Non-evolving ice sheet
• Surface mass balance is computed for both ice sheets
in all CMIP6 experiments
• Good agreement with regional models (RACMO), but
some remaining biases
• CESM2 Arctic climate compares well to reanalysis for
forcing of regional models
RACMO2 CESM2
Land Ice: CESM2 simulations
Ice sheet model development
• More realistic subglacial hydrology
• Improved calving law
• Sub-shelf plume model
• Code speedup
CISM/CESM coupling
• Support for multiple ice sheets, including Antarctica
• CISM coupling to POP and MOM6
• Reduce SMB biases for Greenland
• Would like a lightweight (FV2) version of CESM2 for long transient
simulations of paleo and future climate
Science goal: Reduce uncertainty in sea level rise
Land Ice: Future Directions
CESM Community Ideas
What do people plan on focusing on in the Arctic?
Arctic geoengineering (Tilmes)
Arctic sea-ice with and without geoengineering
RCP8.5 RCP8.5 +
Geoengineering (in 2020)
Whole Atmosphere Community Climate Model (WACCM) Geoengineering Research
Team: Simone Tilmes, Yaga Richter, Mike Mills, Ben Kravitz, and Doug MacMartin
Geoengineering simulations indicate a recovery of Arctic
Sea-Ice
September Arctic Sea-Ice
High Emissions (RCP8.5)
Optimized SRM
Goal: to keep climate at 2020 conditions using stratospheric SO2 injections
Ben Kravitz et al., 2017
What would be the effect of geoengineering on the Arctic?
Effects on sea-ice, land-ice, AMOC, incoming radiation, ecosystem?
Arctic geoengineering (Tilmes)
Coupled Natural Human Systems: Black carbon and the Sea Ice Edge (Bailey)
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Coupled Natural Human Systems: Black carbon and the Sea Ice Edge (Bailey)
Use CESM sea ice concentration as tracer for navigability
- Evaluate likely shipping routes and changes over time.
- Conditions and variability along routes relevant for risk.
- Add other variables at frequency important for navigability (e.g. floe size, derived wave height, ice temperature profile)
- Focuses on CESM-LE and Paris simulations
Maritime Transportation in a Changing Arctic (DuVivier)
Sea Ice thickness satellite emulator (DuVivier)
La
se
r
Ra
da
r
𝒇𝒕𝒐𝒕𝒂𝒍 = 𝒇𝒊𝒄𝒆 + 𝒇𝒔𝒏𝒐𝒘 (1)
𝒉𝒊𝒄𝒆 =𝝆𝒘
𝝆𝒘 − 𝝆𝒊𝒇𝒕𝒐𝒕𝒂𝒍 −
𝝆𝒘 − 𝝆𝒔𝝆𝒘 − 𝝆𝒊
𝒉𝒔𝒏𝒐𝒘 (2)
• Satellites measure freeboard, model outputs thickness.
⍯
• Incorporate on-line satellite emulator to compare CESM with IceSat2 and Cryosat2 observations
Arctic CESM (Holland)
• “Arctic CESM”
– Higher resolution – refined atmosphere grid (7km) and higher ocean/sea ice (~0.1deg)
– Focus on metrics of relevance –navigation, communities, etc.
– Focus on processes of relevance: sea ice wave interactions, landfast ice, snow on ice, permafrost, soil subsidence, hillslope effects, etc.
– *Communities* will help drive the foci. Iterative process!
Figure 1. Project activities and their relationship to project
goals and Research Foci.
Sea ice photo courtesy of Dr. Donald Perovich.
Discussion
• What is the role for CESM in Arctic Science?
• What Arctic science should CESM focus on in the next 5 years?
• What are the critical needs?