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Paradoxical cold conditions during the medieval climate anomaly in the Western Arctic

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ABSTRACT

In the Northern Hemisphere, most mountain glaciers experienced their largest extent in the last millennium during the Little Ice Age (1450 to 1850 CE, LIA), a period marked by colder hemispheric temperatures than the Medieval Climate Anomaly (950 to 1250 CE, MCA), a period which coincided with glacier retreat. Here, we present a new moraine chronology based on 36Cl surface exposure dating from Lyngmarksbræen glacier, West Greenland. Consistent with other glaciers in the western Arctic, Lyngmarksbræen glacier experienced several advances during the last millennium, the first one at the end of the MCA, in ~1200 CE, was of similar amplitude to two other advances during the LIA. In the absence of any significant changes in accumulation records from South Greenland ice cores, we attribute this expansion to multi-decadal summer cooling likely driven by volcanic and/or solar forcing, and associated regional sea-ice feedbacks. Such regional multi-decadal cold conditions at the end of the MCA are neither resolved in temperature reconstructions from other parts of the Northern Hemisphere, nor captured in last millennium climate simulations.

No MeSH data available.


The Lyngmarksbræen glacier and studied sites.(a) Location of existing 10Be moraine chronologies in Baffin and Greenland spanning the MCA (black circles)19 and our new 36Cl moraine record (black triangle). (b) Zoom on the location of the Lyngmarksbræen glacier valley on Disko Island (black triangle), and the Uigordleq valley moraine in west Greenland19 (black circle). (c) Map of the Lyngmarksbræen glacier, showing dated moraines (see Methods) and the location of 36Cl samples (white circles). The reported age uncertainties account for standard deviation, analytical and production rate uncertainties. Satellite image by DigitalGlobe, Inc. Copyright© 201X DigitalGlobe, Inc. www.digitalglobe.com. The figure was created and ArcGis 10.2 Arcinfo single use. http://www.esri.com and Adobe Illustrator CS5 V.15.0.2.
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f1: The Lyngmarksbræen glacier and studied sites.(a) Location of existing 10Be moraine chronologies in Baffin and Greenland spanning the MCA (black circles)19 and our new 36Cl moraine record (black triangle). (b) Zoom on the location of the Lyngmarksbræen glacier valley on Disko Island (black triangle), and the Uigordleq valley moraine in west Greenland19 (black circle). (c) Map of the Lyngmarksbræen glacier, showing dated moraines (see Methods) and the location of 36Cl samples (white circles). The reported age uncertainties account for standard deviation, analytical and production rate uncertainties. Satellite image by DigitalGlobe, Inc. Copyright© 201X DigitalGlobe, Inc. www.digitalglobe.com. The figure was created and ArcGis 10.2 Arcinfo single use. http://www.esri.com and Adobe Illustrator CS5 V.15.0.2.

Mentions: Here, we present a new cosmic-ray exposure moraine chronology of an outlet glacier of the Lyngmarksbræen ice cap (69.36°N; 53.51°W; 32 km2 in 2015), Disko Island, West Greenland (Fig. 1), which flows northeast from a high altitude basalt plateau (up to 995 m above sea level a.s.l.). This land-terminating glacier is not influenced by calving processes induced by oceanic feedbacks, and variations are driven by summer temperature and accumulation making it well-suited to reconstruct past climate conditions.


Paradoxical cold conditions during the medieval climate anomaly in the Western Arctic
The Lyngmarksbræen glacier and studied sites.(a) Location of existing 10Be moraine chronologies in Baffin and Greenland spanning the MCA (black circles)19 and our new 36Cl moraine record (black triangle). (b) Zoom on the location of the Lyngmarksbræen glacier valley on Disko Island (black triangle), and the Uigordleq valley moraine in west Greenland19 (black circle). (c) Map of the Lyngmarksbræen glacier, showing dated moraines (see Methods) and the location of 36Cl samples (white circles). The reported age uncertainties account for standard deviation, analytical and production rate uncertainties. Satellite image by DigitalGlobe, Inc. Copyright© 201X DigitalGlobe, Inc. www.digitalglobe.com. The figure was created and ArcGis 10.2 Arcinfo single use. http://www.esri.com and Adobe Illustrator CS5 V.15.0.2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016737&req=5

f1: The Lyngmarksbræen glacier and studied sites.(a) Location of existing 10Be moraine chronologies in Baffin and Greenland spanning the MCA (black circles)19 and our new 36Cl moraine record (black triangle). (b) Zoom on the location of the Lyngmarksbræen glacier valley on Disko Island (black triangle), and the Uigordleq valley moraine in west Greenland19 (black circle). (c) Map of the Lyngmarksbræen glacier, showing dated moraines (see Methods) and the location of 36Cl samples (white circles). The reported age uncertainties account for standard deviation, analytical and production rate uncertainties. Satellite image by DigitalGlobe, Inc. Copyright© 201X DigitalGlobe, Inc. www.digitalglobe.com. The figure was created and ArcGis 10.2 Arcinfo single use. http://www.esri.com and Adobe Illustrator CS5 V.15.0.2.
Mentions: Here, we present a new cosmic-ray exposure moraine chronology of an outlet glacier of the Lyngmarksbræen ice cap (69.36°N; 53.51°W; 32 km2 in 2015), Disko Island, West Greenland (Fig. 1), which flows northeast from a high altitude basalt plateau (up to 995 m above sea level a.s.l.). This land-terminating glacier is not influenced by calving processes induced by oceanic feedbacks, and variations are driven by summer temperature and accumulation making it well-suited to reconstruct past climate conditions.

View Article: PubMed Central - PubMed

ABSTRACT

In the Northern Hemisphere, most mountain glaciers experienced their largest extent in the last millennium during the Little Ice Age (1450 to 1850 CE, LIA), a period marked by colder hemispheric temperatures than the Medieval Climate Anomaly (950 to 1250 CE, MCA), a period which coincided with glacier retreat. Here, we present a new moraine chronology based on 36Cl surface exposure dating from Lyngmarksbræen glacier, West Greenland. Consistent with other glaciers in the western Arctic, Lyngmarksbræen glacier experienced several advances during the last millennium, the first one at the end of the MCA, in ~1200 CE, was of similar amplitude to two other advances during the LIA. In the absence of any significant changes in accumulation records from South Greenland ice cores, we attribute this expansion to multi-decadal summer cooling likely driven by volcanic and/or solar forcing, and associated regional sea-ice feedbacks. Such regional multi-decadal cold conditions at the end of the MCA are neither resolved in temperature reconstructions from other parts of the Northern Hemisphere, nor captured in last millennium climate simulations.

No MeSH data available.