Open AccessThe Evaluation of the North Atlantic Climate System in UKESM1 Historical Simulations for CMIP6
Author(s) -
Robson Jon,
Aksenov Yevgeny,
Bracegirdle Thomas J.,
DimdoreMiles Oscar,
Griffiths Paul T.,
Grosvenor Daniel P.,
Hodson Daniel L. R.,
Keeble James,
MacIntosh Claire,
Megann Alex,
Osprey Scott,
Povey Adam C.,
Schröder David,
Yang Mingxi,
Archibald Alexander T.,
Carslaw Ken S.,
Gray Lesley,
Jones Colin,
Kerridge Brian,
Knappett Diane,
Kuhlbrodt Till,
Russo Maria,
Sellar Alistair,
Siddans Richard,
Sinha Bablu,
Sutton Rowan,
Walton Jeremy,
Wilcox Laura J.
Publication year - 2020
Publication title -
journal of advances in modeling earth systems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.03
H-Index - 58
ISSN - 1942-2466
DOI - 10.1029/2020ms002126
Subject(s) - climatology , atlantic multidecadal oscillation , climate model , north atlantic oscillation , environmental science , forcing (mathematics) , earth system science , climate system , polar vortex , climate change , climate state , radiative forcing , coupled model intercomparison project , geology , global warming , oceanography , stratosphere , effects of global warming
Earth system models enable a broad range of climate interactions that physical climate models are unable to simulate. However, the extent to which adding Earth system components changes or improves the simulation of the physical climate is not well understood. Here we present a broad multivariate evaluation of the North Atlantic climate system in historical simulations of the UK Earth System Model (UKESM1) performed for CMIP6. In particular, we focus on the mean state and the decadal time scale evolution of important variables that span the North Atlantic climate system. In general, UKESM1 performs well and realistically simulates many aspects of the North Atlantic climate system. Like the physical version of the model, we find that changes in external forcing, and particularly aerosol forcing, are an important driver of multidecadal change in UKESM1, especially for Atlantic Multidecadal Variability and the Atlantic Meridional Overturning Circulation. However, many of the shortcomings identified are similar to common biases found in physical climate models, including the physical climate model that underpins UKESM1. For example, the summer jet is too weak and too far poleward; decadal variability in the winter jet is underestimated; intraseasonal stratospheric polar vortex variability is poorly represented; and Arctic sea ice is too thick. Forced shortwave changes may be also too strong in UKESM1, which, given the important role of historical aerosol forcing in shaping the evolution of the North Atlantic in UKESM1, motivates further investigation. Therefore, physical model development, alongside Earth system development, remains crucial in order to improve climate simulations.