Reconciling the Greenland ice-core and radiocarbon timescales through the Laschamp geomagnetic excursion- review


The article "Reconciling the Greenland ice-core and radiocarbon timescales through the Laschamp geomagnetic excursion" by Richard A. Staff et al. (2019) investigates the discrepancy between the Greenland ice-core and radiocarbon timescales for the period around the Laschamp geomagnetic excursion (LGM). The LGM was a brief period, about 41,000 years ago, when the Earth's magnetic field weakened significantly, before returning to its normal strength. This event is recorded in Greenland ice cores as a sharp decrease in the concentration of cosmogenic radionuclides, such as 10Be and 14C.

The authors of the article argue that the discrepancy between the two timescales is due to an error in the calibration curve used to convert radiocarbon dates to calendar years. The IntCal13 calibration curve, which is the most commonly used curve, is based on a dataset of tree rings that does not extend back to the LGM. This means that the curve is not able to accurately account for the effects of the LGM on the production of cosmogenic radionuclides.

To address this problem, the authors of the article used a peat core from Tenaghi Philippon, Greece, to develop a new calibration curve that is specifically designed for the period around the LGM. The peat core contains a continuous record of 14C dating back to 47,300 years ago. The authors used this record to identify three distinct phases in the build-up to the LGM: a pre-LGM phase, a LGM phase, and a post-LGM phase.

The authors then compared the 14C record from the peat core to the 10Be record from Greenland ice cores. They found that the two records were in good agreement, suggesting that the new calibration curve is accurate. This means that the discrepancy between the Greenland ice-core and radiocarbon timescales is due to an error in the IntCal13 calibration curve.

The findings of this study have important implications for the study of past climate change. The LGM was a time of significant climate change, and the accurate dating of this event is essential for understanding the causes and consequences of this change. The new calibration curve developed by the authors of this study will allow scientists to more accurately date events around the LGM, and this will help to improve our understanding of past climate change.

In addition to the scientific implications, the findings of this study also have practical implications. The Greenland ice-core and radiocarbon timescales are used to date a wide variety of archaeological and environmental records. The accurate dating of these records is essential for understanding human history and the natural environment. The new calibration curve developed by the authors of this study will help to ensure that these records are dated accurately.

Overall, the article "Reconciling the Greenland ice-core and radiocarbon timescales through the Laschamp geomagnetic excursion" is a significant contribution to the field of climate science. The findings of this study will help to improve our understanding of past climate change and will also help to ensure that archaeological and environmental records are dated accurately.

In addition to the information in the article, here are some other things to keep in mind:

  • The LGM was not the only geomagnetic excursion that has occurred in the past. There have been many other excursions, some of which were much larger than the LGM.

  • The causes of geomagnetic excursions are not fully understood. However, it is thought that they may be caused by changes in the Earth's core.

  • Geomagnetic excursions can have a significant impact on the Earth's climate. The LGM, for example, is thought to have caused a global cooling event.

The study of geomagnetic excursions is an active area of research. Scientists are still learning about how these events occur and what their effects are on the Earth's climate. The findings of the study by Staff et al. (2019) are a valuable contribution to this research and will help to improve our understanding of geomagnetic excursions.


Article Snippets

Reconciling the Greenland ice-core and radiocarbon timescales through the Laschamp geomagnetic excursion

IntCal and GICC05 broadly coherent

we use this common production signal to compare between the radiocarbon (IntCal) and Greenland ice-core (GICC05) timescales, utilising the most pronounced cosmogenic production peak of the last 100,000 years

that associated with the Laschamp geomagnetic excursion circa 41,000 years ago

This is the first time that a continuous, non-reservoir corrected 14C dataset has been generated over such a long time span for this, the oldest portion of the radiocarbon timescale.

A fundamental problem in identifying such temporal relationships in palaeo-records, however, is an inability to reliably compare inter-regional records beyond the limits of chronological uncertainty.

Arguably, the best and most-widely cited record of palaeoclimatic change – the key global reference ‘type site’ – is that provided by the Greenland ice-cores

Conversely, the most utilised geochronological technique applied to late Quaternary palaeoenvironmental (and archaeological) sites elsewhere in the world is provided by radiocarbon (14C) dating

in order to compare data between the two timescales, one must assume that the respective 14C and ice-core layer-counted chronologies are consistent – an assumption that must undoubtedly incorporate uncertainties

Here, we utilise the common production signal of the cosmogenic radionuclides 10Be (beryllium-10) and 14C (radiocarbon) to link together the Greenland ice-core and radiocarbon timescales for the oldest ∼10,000 years of the radiocarbon timescale (i.e. the last ∼50,000 years), taking advantage of the most pronounced cosmogenic production peak of the last 100,000 years – that associated with the Laschamp geomagnetic excursion circa 41,000 years ago.

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