Terrestrial Biogeochemistry in UKESM! Anna Harper, Andy Wiltshire, Rich Ellis, Spencer Liddicoat, Nic Gedney, Gerd Folberth, Eddy Robertson, T

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1 Terrestrial Biogeochemistry in UKESM! Anna Harper, Andy Wiltshire, Rich Ellis, Spencer Liddicoat, Nic Gedney, Gerd Folberth, Eddy Robertson, T Davies-Barnard, Doug Clark, Margriet Groenendijk, Chris Jones, Peter Cox! NCAS Forum! 1 Dec. 2015!

2 Motivation! Feedbacks from the terrestrial carbon cycle contribute large uncertainty to future climate scenarios! Changes to vegetation and methane emissions can lead to positive feedbacks! The size of the future land carbon sink is uncertain, and depends on wether plants are fertilised by CO2 or limited by nutrients & climate.! Air quality is affected by biogenic VOCs, which are O3 precursors! Most of the land surface has been modified by humans! There is a need for the next generation of models to answer questions about food production, bioenergy, carbon cycle and climate implications of land use!

3 Motivation! Changes to vegetation and methane emissions can lead to positive feedbacks! Biogenic VOCs can produce O3 and affect air quality! The role that nutrient limitation will play on the future land carbon sink is uncertain! Most of the land surface has been modified by humans! There is a need for the next generation of models to answer questions about food production, bioenergy, carbon cycle and climate implications of land use! Improved/new plant functional types to represent more diverse responses of vegetation to climate change/ variability.! Simulate the emissions of CH4 from wetlands and BVOCs from plants.! Represent N limitation on global plant productivity.! Include carbon cycle impacts of crop harvest.!

4 Improving Physiology with new Plant Extend from 5 to 9 PFTs.! Use N for leaf, root, and stem from the TRY database. This affects:! Plant respiratory costs, & therefore their net C uptake capacity! C/N ratios which determine their propensity to be N limited.! New parameters for calculating Vcmax, which determines photosynthetic capacity.! Update phenology to enforce observed trade-off between Leaf Mass/Area & leaf lifespan, which affects competitiveness of PFTs.! New PFTs have different optimal temperature for photosynthesis! Functional Types! Trees! Grass! Shrubs! broadleaf! needleleaf! C3! C4! evergreen! deciduous! evergreen! deciduous! evergreen! deciduous! tropical! temperate!

5 Site Evaluation of Gross Primary Production Tropical forest Savannah Higher GPP with trait data & new PFTs (blue lines)! Compared to JULES with 5 PFTs, including all updated parameters (JULES9):! Needleleaf evergreen Decreased daily RMSE at 7 sites > both savannahs, 1 NET, both natural grasslands, 1 BDT, + the NDT site.! Increased correlation at 9 sites > both savannahs, all NET, both natural grasslands, 1 BDT + the NDT site.! Grass Needleleaf deciduous Brdlf Dec

6 Vegetation distribution! Present day! Change in fractions, 2090 s s! BT NT C3g C4g SH Soil Based on IPSL-CM5A- LR RCP8.5! Preliminary results: Next step is to test PFTs with HadGEM climate and others!

7 Wetland CH4 emissions! Wetland methane emissions are calculated based on different substrates: soil carbon or NPP.! Methane emissions are passed to UKCA! Using NPP as a substrate increases emissions in the Tropics.! Improvements in the wetland fraction based on updated TOPMODEL parameters (influence of topography on inundation).! Seasonal fraction of wetland in tropics relative to global total Marthews et al. 2015: High-resolution global topographic index values for use in large-scale hydrological modelling. Hydrol. Earth Sys. Sci.

8 BVOC Emissions! Small changes in future global isoprene emissions: Warming increases emissions but CO2 inhibits them! Change in O3 due to isoprene emission change only, ! Locally large impact of isoprene emissions on tropospheric ozone! This work was done a few years ago, but there are new emission factors calculated for the new PFTs! Pacifico et al. 2012, JGR: Sensitivity of biogenic isoprene emissions to past, present, and future environmental conditions and implications for atmospheric chemistr

9 Managed land in JULES: Why! There is already a crop physiological model. The idea here is to represent the effects of management on land cover.! Allow crops to compete for land amongst themselves, so future simulations do not need specific maps of crop types, only a map of the agricultural fraction for each grid cell.! Crops are different from natural plants:! Crops may not be N limited due to fertilizer! Crops may not be water limited due to irrigation! Crops are harvested, so allocation of biomass varies!

10 Managed land in JULES: How! Adding 4 PFTs (2 crop & 2 pasture)! Do not allow competition between new PFT subgroups (natural-crop, natural-pasture, crop-pasture)! Harvest represented by removal of crop litter! Testing of 5 natural+4 agricultural PFTs and 9+4.! There is a minimal impact, with small reductions in soil carbon.! Technical difficulties such as the atmospheric chemistry needs to be able to see 17 land tiles.!

11 Nitrogen cycle! Plants need N to convert CO2 to carbohydrates.! There is plenty of N2 available but it takes energy to convert this to biologically available N.! N availability and the capacity for forests to acquire new sources of N affect CO2 fertilization.! In future projections, nitrogen dynamics reduce the CO2 fertilisation effect and increase the terrestrial carbon loss due to warming.! Two models with N cycle (NCAR-CESM1-BGC & NCC-NorESM-ME) had a muted response: CO2 fertilization effected was limited in the biogeochemical experiments.! Arora et al. 2013: Carbon-concentration and carbonclimate feedbacks in CMIP5 ESMs, J. Climate!

12 JULES CN! Represents soil and vegetation nitrogen processes! TRIFFID DGVM receives NPP & N limitation reduces the NPP! N pools for roots, wood, and leaves! Soil N model based on Roth-C!

13 Global JULES CN GtC in AR5 models 2xCO2 > 1xCO2 in all cases! JULES-CN < JULES-C for each CO2 scenario! 2xCO2 CN + 2 C > 2xCO2 CN: greater N availability because of increased mineralisation due to warmer soil! Trees fare better than grasses with 2xCO2 and with N limitation.!

14 Near-term goals! We have begun testing all of the developments together.! Evaluation focus on:! Distribution of PFTs! Global GPP (~120 Pg C/yr) and NPP (~50% of GPP)! Global soil C (~1500 Pg C), and vegetation carbon (~ Pg C)! Fluxnet sites (24 with GPP)! Seasonal cycle of CO2 at Mauna Loa! NPP response at Duke and Oak Ridge! FACE sites (& others)! Including optimised parameters from! adjules!

15 Development timeline! Developments for JULES-CN are in place.! Online testing beginning now.! We have between now and ~June 2016 to:! Tune offline JULES! Test online JULES for unexpected coupling issues.! This will get it into UKESM-0.5!

16 Post-UKESM1 developments! RED: Each PFT is divided into mass classes so successional stages can be modelled to improve carbon uptake following land use! Further development of land use/managed land/crop model! Permafrost: Need deeper soils with more soil layers, organic soils!