CESM Cross Working group meeting – Navigating the New with CESM

Andrew Gettelman, Marika Holland, Alice DuVivier June 19, 2019

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 Directions

Where are we now in the Arctic? Where are we going? Atmosphere: Where we are

• CAM6 = Much better polar clouds • Improved TOA and surface fluxes

TOA Cloud Radiative Effect CESM2-CAM6: Better Arctic Clouds

CAM6 CAM6 CAM5 Obs (ARM) Atmosphere: Where we are going

• 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

Example: Simulating Observed Size Distributions Obs in CESM2 over the S. Ocean from SOCRATES in 2018 (Hobart & South) Atmosphere: Where we are going (High Res)

• 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/ 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 Sea Ice: Where we are

CESM2: • 8 sea ice, 3 snow vertical levels (doubled/tripled respectively) CAM6

• Mushy layer thermodynamics

• Mean climate, trends are pretty good

• Interesting differences due to atmosphere. WACCM6

Obs From Holland, Bailey, and DuVivier 1979-2014 average CAM6 WACCM6 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 – /snow – using upcoming MOSAiC observations 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 and cold region research priorities

David Lawrence Climate and Global Dynamics Laboratory With contributions from Sean Swenson, Christina Schaedel, and Charlie Koven Benchmarking models against field experiments

Growing season Artificial warming gross primary productivity (GPP) Snow fence experiment

Schaedel et al, 2018 Abrupt permafrost thaw

Thermokarst lakes

20% of permafrost domain has high ice content and is potentially subject to abrupt thaw and rapid

increases in CO2 and CH4 emissions

Hillslope failure

Steven Kazlowski/NPL

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 Ground heat flux Sub-surface lateral water flux Water Lateral diffusive heat flux track flow Frozen soil Saturated soil Snow Ice lens

N Upland system Ground heat flux Sub-surface lateral water flux Water Lateral diffusive heat flux track flow Frozen soil Saturated soil Snow Ice lens

after ice melt after ice melt Lowland system Ground heat flux Sub-surface lateral water flux Water Lateral diffusive heat flux track flow Frozen soil Saturated soil Snow Ice lens

after ice melt after ice melt Impacts of abrupt Ground heat flux thaw on infrastructure Sub-surface lateral water flux Water Lateral diffusive heat flux track flow Frozen soil Saturated soil Snow Ice lens

(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) Land Ice: model development 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: CESM2 simulations

Non-evolving ice sheet RACMO2 CESM2 • 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

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. Land Ice: Future Directions

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 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 Arctic geoengineering (Tilmes)

Geoengineering simulations indicate a recovery of Arctic Sea-Ice

Goal: to keep climate at 2020 conditions using stratospheric SO2 injections

Ben Kravitz et al., 2017 September Arctic Sea-Ice

High Emissions (RCP8.5) Optimized SRM

What would be the effect of geoengineering on the Arctic? Effects on sea-ice, land-ice, AMOC, incoming radiation, ecosystem? Coupled Natural Human Systems: Black carbon and the Sea Ice Edge (Bailey)

Aice_Free_Length 1980 Aice_Free_Length 2000 2 0 4 0 00 240 30 0 3 0 18 18 0 1260 24 1260 24108260 0 168200 60

60

60 0 0 6 0 8 400 6 1 20 0 160 30 60 0 40 8120 6 241120 0 23 2400300 080 3

Aice_Free_Length 2020 3 Aice_Free_Length 2040 0 0 00 240 03 24 18 3 0 1182600 12 00 10260 240106820 060 214830 60 120

120 0 0 6 6 40 00 2 6 60 0 61020 04 0 16800 40 60 30 234010080 32 3020

Aice_Free_Length 2060 Aice_Free_Length 2080 0 30 0 0 30 182 4 182 30 4800 0 602 0 0 204600 1021 18 312024

6 6 0 0 180

1 2 0

0 8 120 1 1 0 8 04 0 0 0 0 6 60 60 0 60 2 0 60 00 3 36000 4 3 2340 2 Coupled Natural Human Systems: Black carbon and the Sea Ice Edge (Bailey) Maritime Transportation in a Changing Arctic (DuVivier)

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 Sea Ice thickness satellite emulator (DuVivier)

• Satellites measure freeboard, model outputs thickness. ⍯ • Incorporate on-line satellite emulator to compare CESM

with IceSat2 and Cryosat2 observations

Laser Radar

풇풕풐풕풂풍 = 풇풊풄풆 + 풇풔풏풐풘 (1)

흆풘 흆풘 − 흆풔 풉풊풄풆 = 풇풕풐풕풂풍 − 풉풔풏풐풘 (2) 흆풘 − 흆풊 흆풘 − 흆풊 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.

Figure 1. Project activities and their relationship to project – *Communities* will help drive goals and Research Foci. the foci. Iterative process! 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?