Monday, January 25, 2021, 12:00PM - 1:00PM
This is a climate science story about resolution, time, and technology. It spans many decades, across ice core camps and continents. In the early days of this story, ice core science was just beginning in Denmark in the 1960s. Perhaps improbably, a beer bottle plays a central role. When it was discovered (using that beer bottle) that water isotopes in passing storm fronts are dependent on the condensation temperature in a cloud, great minds realized this could be valid backwards in time using “old water” in glacial ice. Expeditions were launched, and eventually ice cores were recovered in Greenland. Scientists eventually learned about abrupt climate change, and how the climate system can shift within decades. Later work would go on to show these abrupt shifts in Greenland occur within only a few years. Technology progressed over the decades, taking us from 1m sampling resolution, to 5cm, and most recently, to mm-scale resolution. While early ice core studies could interpret climate variability at decadal-to-centennial scales, we can now interpret climate at sub-annual scales, down to the summer and winter seasons. We have essentially unlocked the full continuum of climate variability, with some caveats for smoothing processes that occur naturally, like firn diffusion. In this talk, I will step through time using the memoir of Willi Dansgaard, “Frozen Annals: Greenland Ice Sheet Research''. I will progressively show how each ice core project of the past unlocked higher-frequency climate information, culminating with a recent project in West Antarctica. I will focus on the WAIS Divide ice core (WDC). Sampled at mm-resolution, it is the highest temporal resolution and longest continuous climate record even recovered. In particular, I will discuss changes in the strength of interannual variability across the last glacial-interglacial cycle, and summer and winter variability for the entire Holocene. I will explain how these results tie together the farthest reaches of our planet, from the ice-age ice-sheets in the north, to the rainforests of the tropical south Pacific, to the isolated regions of West Antarctica, and within it all, how orbital forcing plays a clear role in our climate system (as expected).