Chronological analysis of δ18O data from the NGRIP ice core (Greenland), characteristics of solar climate, and large-scale climatic events in the Northern Hemisphere during the Holocene

Data from the isotopic oxygen composition of Greenland ice cores form one of the foundations of isotopic geochronology and climate stratigraphy of the Neopleistocene and Holocene (Petite et al., 1999; Rasmussen et al., 2008, 2014; Cheng et al., 2019). There is a noted lack of correlation between δ18O of ice cores and changes in the characteristics of solar climate (the average absolute value of the correlation coefficient is 0.087). No significant correlation of δ18O of ice cores has been found between individual boreholes in Greenland. Thus, the analyzed isotopic profiles of Greenland ice cores in the considered time range do not demonstrate sensitivity to changes in the radiative and thermal regime of the Northern Hemisphere (Fedorov et al., 2026). The effects of isotopic fractionation found for the present time (Dansgaard et al., 1973) and the relationship of the isotopic oxygen composition of atmospheric precipitation with temperature are not preserved in the ice cores due to mass exchange processes in the glacier, active hydrodynamic conditions (layered movement, formation and closure of cracks), and ice diagenesis processes (Fedorov, 2025; Fedorov et al., 2026). In this regard, to determine the climatic informative value of the δ18O indicator on a Holocene scale, it seems relevant to chronologically compare the δ18O data of the NGRIP ice core (Greenland) with known climatic events in the Holocene. As a result of the conducted comparison, a graphical fixation of the isotopic oxygen composition of the NGRIP ice core during the active phase of the last deglaciation in Europe and North America was identified. At the same time, the isotopic composition of the NGRIP ice core lacks responses to large-scale Holocene events: the Medieval Warm Period (Little Optimum) and the Little Ice Age. There is also no manifestation in the dynamics of δ18O of the NGRIP ice core of extremes in summer intensity in the Northern Hemisphere in the cycle of climatic precession, which defines the main dispersion in centennial variations of incoming solar radiation—the primary source of heat on Earth. Therefore, the assertion that the δ18O indicator can serve as a basis for geochronology and climate stratigraphy and as a paleothermometer does not appear convincing, as it is based solely on graphical synchronization with one of the three discussed large-scale events.