Some notes on the interpretation and reliability of malacological proxies in paleotemperature reconstructions from loess- comments to Obreht et al.'s “A critical reevaluation of paleoclimate proxy records from loess in the Carpathian Basin”

Abstract

The paper of Obreht et al., 2019 expresses strong criticism of malacothermometer-based summer paleotemperature reconstructions for the southern parts of the Carpathian Basin. Claims are given that malacological data yield anomalously higher temperatures for the glacials and the LGM compared to other proxy data indicating summer temperatures to be well below 15 °C even 10 °C. To support their arguments interpretations are provided on malacological results of two profiles from the region with data presented by depth rather than chronology making the assessment of chronological claims difficult. In this work we aim to pinpoint that their record and interpretations are burdened by potential biases of alleged sampling, stratigraphic misassignment of the samples, high uncertainty of the chronology and others, especially relevant for the LGM part of the profile leading to flawed conclusions. A new chronology for the LGM was also developed to better confine our mollusk data and give further support to our interpretations and tackle potential inconsistencies in accumulations. Besides our malacological data, some other regional proxy records, outputs of global and regional climate models clearly contradict claims that summer temperatures were lower than 10C° during the LGM in the Carpathian Basin. The 10 °C temperature gradient between the northern parts and southern parts of the basin for the LGM claimed by Obreht et al. (2019) also contradict our data showing only a couple of degrees difference. Recent global and regional climate models indicate much warmer conditions with only 3–6 °C lower global temperatures for the LGM than given by older models and claimed by Obreht et al., 2019. When modern summer temperatures of 21–22 °C are considered, the yielded temperatures are perfectly in line with malaco-thermometric mean July temperature values of 15–18 °C reconstructed for the area.