IDP Ice Core Working Group (IDP-ICWG): Ice Core Research Priorities in Greenland

Rapid warming is profoundly affecting Arctic ecosystems, accelerating Greenland Ice Sheet (GrIS) melting, reducing sea ice cover, raising sea level and endangering coastal societies and infrastructure. However, large uncertainties remain about the projected rate and magnitude of Arctic cryosphere and ecosystem change in the coming decades under plausible 21st century emissions scenarios. Greenland ice cores revolutionized our understanding of climate change when they revealed a series of abrupt climate change events (CCEs) in the glacial and Holocene. The paleorecord indicates that Arctic processes (e.g., deep-water formation and sea ice) played a central role in past CCEs, but we still lack a comprehensive understanding of their triggers and dynamics. Climate model projections suggest that warming and increased meltwater runoff will weaken the Atlantic circulation in the 21st century, a scenario similar to past CCEs. Understanding how such processes occurred in the past is needed to better predict nonlinear responses to anthropogenic warming that will have impacts well beyond the Arctic. It is particularly challenging to quantify the impact of human activities on Arctic systems because of the extremely short instrumental period, often limited to the satellite era since 1979. Details of pre-instrumental Arctic processes over the Common Era and the evolution of human impacts from the onset of industrialization are needed to clarify future vulnerabilities.

These critical knowledge gaps can be addressed by a series of new ice cores and state-of-the-art, high-resolution analyses that are developed in a convergent framework that incorporates a diverse research community. This new approach will focus on the following research priorities:

1) Arctic Change and GrIS Instability during Warm Periods: The Holocene Thermal Maximum (HTM; ca. 5,000-9,000 years BP) and Eemian interglacial (130,000-115,000 years BP) are periods when Arctic summers were at least 3-5°C warmer than today, making them valuable analogs for future warming. A strategy that involves ice cores to bedrock in Northern and Southern Greenland will target the GrIS response to these past warm intervals and help predict impacts in a warming climate.

2) Mechanisms of Abrupt Climate Change: The regional and global expression of abrupt CCEs during the last glacial period (Dansgaard-Oeschger and Heinrich events) and Holocene (8.2 ka event, Medieval Climate Anomaly/Little Ice Age, and the Industrial Era) provide a critical perspective on the complex interaction of various Earth System components. The spatial pattern and detailed anatomy of CCEs across Greenland remain elusive but can be accessed with a combined shallow/intermediate/deep drilling approach.

3) The Evolution of Human Impacts on the Arctic: The complex interaction of human emissions (greenhouse gases, pollutants) and activities (biomass burning) with natural forcing and feedbacks (volcanic eruptions, oceanic and atmospheric circulation, sea ice, GrIS mass balance, sea level) must be resolved on a seasonal basis throughout Greenland with agile drilling of shallow cores. Societally relevant predictions regarding future changes in the coupled human/natural system require these data.