Abstract
To better understand what determines the Last Glacial Maximum (LGM) cold and dry climate, a suite of numerical experiments with the Nanjing University of Information Science and Technology Earth System Model version 1 are conducted to assess the relative contributions of individual external forcings, including greenhouse gases (GHGs), ice sheets (IS), land-sea configuration (LSC) and the Earth’s orbital parameters, and the contribution of their combination in the LGM mean climate change. Results of the single-forcing sensitivity experiments not only reveal spatial patterns of temperature and precipitation changes that are different from today’s climate, but also shed light on understanding the underlying processes through which each forcing contributes to the formation of the LGM climate. The full forcing experiment simulates a 5.3 K global cooling and an 11.8% reduction of the global mean precipitation, thus yielding a hydrological sensitivity of 2.2% K−1, which is larger than that caused by the present-day GHG forcing. The excessive hydrological sensitivity is primarily attributed to the land-sea configuration change, since its dynamic factor (circulation change) amplifies the precipitation reduction at the tropical convergence zones over both hemispheres. The GHG forcing is the largest contributor to the tropical cooling, whereas ice sheets are responsible for the large hemispheric temperature asymmetry and meridional gradients of the zonal mean temperature change during the LGM period. The LGM precipitation is characterized by decreased precipitation over the Indo-Pacific Ocean and a salient wave train pattern over the Northern Hemisphere (NH). The GHG and LSC forcings are the major contributors to the former since they can change the Indo-Pacific sea surface temperature and the associated Walker circulation, while ice sheets lead to the wave train pattern over the NH by changing the North Atlantic jet stream/storminess and shifting the Intertropical Convergence Zone southward. The climate responses to the LGM forcings are nonlinear. The nonlinearity mainly comes from the overlapping effects induced by the IS and LSC forcings.
| Original language | English |
|---|---|
| Pages (from-to) | 1661-1679 |
| Number of pages | 19 |
| Journal | Climate Dynamics |
| Volume | 53 |
| Issue number | 3-4 |
| DOIs | |
| State | Published - Aug 15 2019 |
Funding
This work was jointly supported by the National Key R&D Program of China (2017YFA0603801 and 2016YFA0600401), National Natural Science Foundation of China (41420104002), Natural Science Foundation of China of Jiangsu Province (BK20180812), the social commonweal research program of Ministry of Science and Technology (201505013), National Basic Research Program of China (2015CB452803), Program of Innovative Research Team of Jiangsu Higher Education Institutions of China, and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD). This is the SOEST pulication number of 10669, IPRC pulication number of 1370 and the ESMC publication number of 254. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.