据了解，更新世冰期表现出突然的Dansgaard-Oeschger（DO）气候振荡，提供了地球系统临界点的主要例子——可能导致不可逆转变化的突变。格陵兰冰芯提供了DO气候变率的关键记录，但气体校准的温度变化幅度估计仅限于格陵兰中部和西北部。
研究团队利用格陵兰岛南部（Dye 3）和东部沿海（Renland）的冰芯δ15N-N2记录，来校准当地的水同位素温度计，并提供整个格陵兰岛范围内DO事件强度的空间特征。研究人员将这些数据与现有的δ18O、氘过量和积累速率记录结合起来，创建了DO对格陵兰岛影响的多代理“指纹”。同位素支持的气候模型，在模拟观测的多代理DO事件影响方面具有一定的技巧，研究利用这些模型进行了一系列理想化的模拟，以确定在解释DO变率方面至关重要的北大西洋地区。
实验结果表明，冬季在亚极环流中的海冰变化，而不是通常所说的北欧海，是解释格陵兰岛观测到的DO影响的充分和必要条件，无论其远端原因是什么。湿度标记实验支持这样一种观点，即格陵兰DO同位素信号几乎完全可以通过水汽来源分布的变化来解释，并且与传统解释相反，在DO转变过程中，现场温度不是δ18O的主要控制因素。本研究提供了一个全面的、多代理的综合了格陵兰岛突发性DO气候变率的数据模型。
附：英文原文
Title: The Greenland spatial fingerprint of Dansgaard–Oeschger events in observations and models
Author: Buizert, Christo, Sowers, Todd A., Niezgoda, Kyle, Blunier, Thomas, Gkinis, Vasileios, Harlan, Margaret, He, Chengfei, Jones, Tyler R., Kjaer, Helle A., Liisberg, Jesper B., Menking, James A., Morris, Valerie, Noone, David, Rasmussen, Sune Olander, Sime, Louise C., Steffensen, Jrgen P., Svensson, Anders, Vaughn, Bruce H., Vinther, Bo M., White, James W.C.
Issue&Volume: 2024-10-21
Abstract: Pleistocene Ice Ages display abrupt Dansgaard–Oeschger (DO) climate oscillations that provide prime examples of Earth System tipping points—abrupt transition that may result in irreversible change. Greenland ice cores provide key records of DO climate variability, but gas-calibrated estimates of the temperature change magnitudes have been limited to central and northwest Greenland. Here, we present ice-core δ15N-N2 records from south (Dye 3) and coastal east Greenland (Renland) to calibrate the local water isotope thermometer and provide a Greenland-wide spatial characterization of DO event magnitude. We combine these data with existing records of δ18O, deuterium excess, and accumulation rates to create a multiproxy “fingerprint” of the DO impact on Greenland. Isotope-enabled climate models have skill in simulating the observational multiproxy DO event impact, and we use a series of idealized simulations with such models to identify regions of the North Atlantic that are critical in explaining DO variability. Our experiments imply that wintertime sea ice variation in the subpolar gyre, rather than the commonly invoked Nordic Seas, is both a sufficient and a necessary condition to explain the observed DO impacts in Greenland, whatever the distal cause. Moisture-tagging experiments support the idea that Greenland DO isotope signals may be explained almost entirely via changes in the vapor source distribution and that site temperature is not a main control on δ18O during DO transitions, contrary to the traditional interpretation. Our results provide a comprehensive, multiproxy, data-model synthesis of abrupt DO climate variability in Greenland.
DOI: 10.1073/pnas.2402637121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2402637121