Ice Cores Tell the Tale of an Incredibly Powerful Solar Storm That Hit the Earth 9,200 Years Ago

For decades, climate researchers and Earth scientists have used cores from ice sheets in the Arctic and Antarctic to better understand Earth’s climate history. Given how sensitive our atmosphere and climate are to the Sun, these ice cores are also a record of Solar activity. In a recent analysis of ice cores from Greenland and Antarctica, a research team led by Lund University in Sweden found evidence of an extreme solar storm that occurred about 9,200 years ago – when solar activity was believed to be one of the Sun’s more “quiet” phases.

The team consisted of researchers from Lund’s Department of Geology & Quaternary Sciences, the Alfred Wegener Institute (AWI) for Polar and Marine Research, the Laboratory of Ion Beam Physics at ETH Zürich, and the Ice Dynamics and Paleoclimate team (part of the British Antarctic Survey) at Cambridge University. Their results appeared in a paper that was recently published by Nature Communications.

The Sun is absolutely essential for most life on Earth and the processes that ensure continued habitability. However, there is a flip side to this relationship, which comes in the form of the “Sunspot Cycle,” an 11-year period where the number and location of sunspots on the surface rises and falls. During periods of peak sunspot activity (a “solar maximum”), the Sun’s surface becomes more energetic, resulting in increased solar wind and the occasional solar flare.

When these reach Earth’s atmosphere, it can lead to geomagnetic storms (or solar storms) that seriously impact Earth’s infrastructure – like power outages and communication disturbances. By developing predictive models that could anticipate solar activity (and solar storms), advanced warning systems could be created that would let us prepare for the ensuing disruption. But predicting solar storms is not an easy task.

It is currently believed that solar storms are more likely during an active phase of the Sun (solar maximum). However, according to the study led by Lund University researchers, this may not always be the case for particularly large storms. While analyzing ice cores from Greenland and Antarctica, the team found peaks of radioactive isotopes – beryllium-10 and chlorine-36 – produced by high-energy cosmic particles associated with solar storms.

This was a surprising find since the event that created these isotopes occurred roughly 9125 years before the present day (ca. 7176 BCE). This coincides with the “Neolithic Period,” a historic era where humanity was making the transition from hunting and gathering to agriculture and sedentary living. At this time, it is believed that Earth was less exposed to such energetic events. As co-author Raimund Muscheler, a geology researcher at Lund University, said:

“We have studied drill cores from Greenland and Antarctica, and discovered traces of a massive solar storm that hit Earth during one of the sun’s passive phases about 9,200 years ago. This is time-consuming and expensive analytical work. Therefore, we were pleasantly surprised when we found such a peak, indicating a hitherto unknown giant solar storm in connection with low solar activity.”

Analyzing ice cores led the researchers to their surprising results. Credit: Raimund Muscheler

The implications of this find could be immensely significant when it comes to mitigating the danger posed by solar storms. If a storm of the same magnitude were to happen today, it would have devastating consequences for Earth and space exploration efforts. In addition to triggering power outages all over the planet, disabling communications, and endangering air traffic control, it would damage satellites and make it very difficult to communicate with astronauts or long-range missions.

Knowing how and when they can occur (regardless of the solar spot cycle) is essential to ensuring that people and infrastructure (whether it’s here on Earth or in space) remain safe and sound. “These enormous storms are currently not sufficiently included in risk assessments,” Muscheler added. “It is of the utmost importance to analyze what these events could mean for today’s technology and how we can protect ourselves.”

Further Reading: Lund University, Nature Communication