TITLE: Studying Uncertainties in Climate-Terrestrial Biogeochemical Feedbacks in the Northern High Latitudes using a Flexible Earth System Modeling Framework


SESSION TITLE: B22D. Improving Predictions of the Global Carbon Cycle and Climate in Earth System Models: New Mechanisms, Feedback Sensitivities, and Approaches for Model Benchmarking I

AUTHORS: Rahul Barman1, Forrest M. Hoffman2, David M. Lawrence3, Yang Song1, Prasanth Meiyappan1, Atul K. Jain1, Robert L. Jacob4, Mariana Vertenstein3

1Atmospheric Sciences, UIUC, Urbana, IL, United States.
2Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States.
3Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, CO, United States.
4Mathematics and Computer Science Division, Argonne National Laboratory, Argonne, IL, United States.

ABSTRACT BODY: Uncertainties in the representation of terrestrial biogeochemistry in land surface models (LSMs), together with their long spin-up time requirements, contribute to the many challenges inherent in coupled Earth system models (ESMs). Here we present a recently developed ESM framework, designed to incorporate multiple LSMs into an existing ESM. This ISAM-CESM framework provides an alternative LSM, the Integrated Science Assessment Model (ISAM), coupled to the NCAR Community Earth System Model (CESM1). The purpose of this general modeling framework is to carry out equivalent climate simulations using multiple LSMs with the rest of the component models being the same, allowing a more direct comparison of the effects of different land surface representations on corresponding feedbacks to climate change.

In this presentation, we will analyze the role of different biogeochemistry representations and the effects of different land surface processes on climate-carbon cycle feedbacks using the ISAM and the NCAR Community Land Model (CLM4), the two LSMs currently available in the ISAM-CESM framework. Both ISAM and CLM4 contain fully prognostic, coupled carbon-nitrogen models, integrated with detailed representation of terrestrial biogeophysics. Biogeophysical schemes in the ISAM have been adapted from the CLM4, its precursor CLM3.5, and the Common Land Model (CoLM); however, the representation of the biogeochemistry of carbon nitrogen cycles are structurally different in the two models, making them suitable for inter-comparison. The aim of this study is to understand those differences and better attribute their roles in varying responses of the land surface to future climate change.

We will compare the 20th century predictions of gross primary productivity (GPP) and annual cycle of CO2 from offline land simulations of ISAM and CLM4, using the newly available CRU-NCEP climate forcing data, in the CESM1 modeling framework to study the response of alternate land surface models. These results will be compared with contemporary observations using the diagnostics from the Carbon-Land Model Intercomparison Project (C-LAMP). While the comparison will be carried out at the global scale, special focus will be given to the Northern High latitude regions, because these regions may be especially susceptible to strong feedbacks as a consequence of rapid and abrupt climate change.

[0414] BIOGEOSCIENCES / Biogeochemical cycles, processes, and modeling,
[0416] BIOGEOSCIENCES / Biogeophysics,
[0475] BIOGEOSCIENCES / Permafrost, cryosphere, and high-latitude processes,
[0429] BIOGEOSCIENCES / Climate dynamics.

SPONSOR NAME: Rahul Barman

CONTACT: Rahul Barman <rbarman2 at illinois dot edu>