Melt in the Greenland EastGRIP ice core reveals Holocene warm events

Abstract

Abstract. We present a record of melt events obtained from the East Greenland Ice Core Project (EastGRIP) ice core in central northeastern Greenland, covering the largest part of the Holocene. The data were acquired visually using an optical dark-field line scanner. We detect and describe melt layers and lenses, seen as bubble-free layers and lenses, throughout the ice above the bubble–clathrate transition. This transition is located at 1150 m depth in the EastGRIP ice core, corresponding to an age of 9720 years b2k. We define the brittle zone in the EastGRIP ice core as that from 650 to 950 m depth, where we count on average more than three core breaks per meter. We analyze melt layer thicknesses, correct for ice thinning, and account for missing layers due to core breaks. Our record of melt events shows a large, distinct peak around 1014 years b2k (986 CE) and a broad peak around 7000 years b2k, corresponding to the Holocene Climatic Optimum. In total, we can identify approximately 831 mm of melt (corrected for thinning) over the past 10 000 years. We find that the melt event from 986 CE is most likely a large rain event similar to that from 2012 CE, and that these two events are unprecedented throughout the Holocene. We also compare the most recent 2500 years to a tree ring composite and find an overlap between melt events and tree ring anomalies indicating warm summers. Considering the ice dynamics of the EastGRIP site resulting from the flow of the Northeast Greenland Ice Stream (NEGIS), we find that summer temperatures must have been at least 3 ± 0.6 ∘C warmer during the Early Holocene compared to today.

SE‐Dome II Ice Core Dating With Half‐Year Precision: Increasing Melting Events From 1799 to 2020 in Southeastern Greenland

“…Comparing our results with Westhoff et al. (2022), we determine that the SE‐Dome site is more likely to melt, and form MLs than the EGRIP in the northern GrIS.…”

“…Westhoff et al. (2022) reported that three MLs were detected in the EGRIP ice core from 1800 to 1964, whose thicknesses are observed. The 1889 CE melt event consists of two MLs with a total of 8.5 mm thickness and the 1950 CE melt event, with a ML of 3.1 mm thickness.…”

Chemical and visual characterisation of EGRIP glacial ice and cloudy bands within

“…Below a depth of 1375 m (bag 2500, 14.6 ka b2k (Gerber et al, 2021)) constant settings were used. We do not investigate cloudy bands from the Holocene (Westhoff et al, 2022) and cloudy bands showing deformation features to reduce one factor of complication. Andersen et al (2006) and Winstrup et al (2012) showed that cloudy bands appear in an annual cyclicity and that a single cloudy band, i.e.…”

“…The principal minerals are gypsum, quartz, feldspar, and mica and mineral diversity decreases slightly with depth. However, various sulfate-minerals, such as Mg-/Na-/K-sulfates or bloedite, were found in the upper 900 m. In addition, visual stratigraphy was measured continuously on the EGRIP ice core (Westhoff et al, 2021(Westhoff et al, , 2022.…”

Contrasted geomorphological and limnological properties of thermokarst lakes formed in buried glacier ice and ice-wedge polygon terrain

“…7c). Summer melt layers from the Agassiz Ice Cap and Greenland ice sheet provide robust records of warmer events during the Holocene (∼ 7-8 ka; Fisher et al, 1995;Westhoff et al, 2022). These warmer periods likely initiated or accelerated the ice melt when (1) a thin layer of sediments covered the ice or (2) topographic depressions allowed the accumulation of snow and water, hence overall warmer conditions, which further accelerated the melting of the buried glacier ice.…”