Changes in tropical and extratropical hydroclimate during the Last Millennium

Pedro José Roldán-Gómez,Camilo Melo-Aguilar,Jesús Fidel González-Rouco,Jason Smerdon

doi:10.5194/ems2022-285

Abstract

&lt;p&gt;Reconstructions of the Last Millennium (LM) suggest coordinated changes in the hydroclimate of separate regions. This happens in regions of North America, North Africa and Europe for the periods of the Medieval Climate Anomaly (MCA; ca. 950&amp;#8211;1250 CE) and the Little Ice Age (LIA; ca. 1450&amp;#8211;1850 CE), but also in tropical areas, where consistent changes are found in regions of South America, East Africa, Southeast Asia and the Indo-Pacific basin. For extratropical areas, changes in the hydroclimate have been mostly linked to changes in variability modes like the Northern (NAM) and Southern Annular Modes (SAM), while in tropical areas they are mostly associated to alterations in the position and intensity of the Intertropical Convergence Zone (ITCZ).&lt;/p&gt;&lt;p&gt;&lt;span&gt;To assess these large-scale changes in the hydroclimate of the LM and the mechanisms explaining them&lt;/span&gt;&lt;span&gt;, &lt;/span&gt;&lt;span&gt;climate simulations from the Community Earth System Model - Last Millennium Ensemble (CESM-LME) have been analysed. &lt;/span&gt;&lt;span&gt;T&lt;/span&gt;&lt;span&gt;o assess the consistency of the results for different regions&lt;/span&gt;&lt;span&gt;, t&lt;/span&gt;&lt;span&gt;hese analyses have been &lt;/span&gt;&lt;span&gt;also&lt;/span&gt;&lt;span&gt; compared with the information provided by proxy-based datasets, including the Drought Atlases for Europe (&lt;/span&gt;&lt;span&gt;OWDA), North America (NADA), Asia (&lt;/span&gt;&lt;span&gt;MADA)&lt;/span&gt;&lt;span&gt;, &lt;/span&gt;&lt;span&gt;Mexico (MXDA), &lt;/span&gt;Eastern Australia and New Zealand&lt;span&gt; (ANZDA), &lt;/span&gt;&lt;span&gt;the Paleo Hydrodynamics Data Assimilation product (PHYDA) and the Last Millennium Reanalysis (LMR).&lt;/span&gt;&lt;/p&gt;&lt;p&gt;Simulations show that changes in the hydroclimate of extratropical and tropical regions of the Atlantic Ocean basin are mainly linked to changes in external forcing factors, while for the tropical areas of the Pacific and Indian Ocean basins, there is a significant contribution of internal variability. The understanding of the mechanisms behind these large-scale changes could help not only to better characterize the evolution of the hydroclimate of tropical and extratropical regions, but also the ability of the model simulations to reproduce the behavior of hydroclimate depending on the region.&lt;/p&gt;

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