Global Climatic Zones in the Last Glacial Maximum Estimated From Assimilated Temperature Data

ABSTRACT The global climatic zones (GCZs) of the Last Glacial Maximum (LGM) were estimated using the k ‐means++ clustering, an unsupervised machine learning algorithm, to improve the reliability of the LGM GCZs. On average, the LGM GCZ boundaries shifted toward the equator by approximately 13° in latitude. This latitudinal shift was pronounced at low latitudes on seasonal and hemispheric averages, reaching approximately 16° at the tropics/warm temperate boundary. The LGM polar (subpolar) zone in the high latitudes of the Northern Hemisphere expanded markedly during the boreal winter (summer), reflecting ice sheet expansion. The analysis confirms a greater latitudinal shift in the Northern Hemisphere than in the Southern Hemisphere and a greater shift in the boreal summer than in the boreal winter.