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?