Moisture Source Tagging Confirming the Polar Amplification Effect in Amplifying the Temperature-δ18O Temporal Slope Since the LGM

• Published in: Atmosphere
• Main Authors: Jian Guan, Zhengyu Liu, Guangshan Chen
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2020
• Subjects: water isotope–temperature relation; temporal slope; spatial slope; polar amplification; moisture tagging; Meteorology. Climatology; QC851-999; Greenland; ice core; North Greenland
• Online Access: https://doi.org/10.3390/atmos11060610; https://doaj.org/article/5db04e923c0440a59aecb47be1e0e47b

Stable water isotopologues in paleoclimate archives (δ18O) have been widely used as an indicator to derive past climate variations. The modern observed spatial δ18O-temperature relation in the middle and high latitudes has been used to infer the paleotemperatures changes from ice core data. However, various studies have shown that the spatial slope is larger than the temporal slope at the drill site by a factor of 2. Physically, the different spatial and temporal slope has been suggested to result from the amplified local surface air temperature cooling in the polar region at Last Glacial Maximum (LGM), according to the slope ratio equation derived in our previous study. To explicitly confirm the “polar amplification” effect in understanding the differences between temporal and spatial isotope–temperature relations, here we use the same isotope-enabled atmospheric general circulation model with a moisture-tracing module embedded to quantitatively estimate the contributions of different sources to the precipitated heavy oxygen isotopes in the middle and high latitudes. Our results show that the major sources of δ18O in precipitation over middle and high latitudes are from oceans where the sea surface temperature cooling at Last Glacial Maximum (LGM) is less than −2 ℃, while the local moisture sources with a higher cooling can be also relevant for polar regions, such as north Greenland. Additionally, the neglect of the strengthened local inversion layer strength at LGM could be the main cause for the overestimated source temperature cooling by the slope ratio equation, especially for the polar regions in the Northern Hemisphere.