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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.

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Volcanic forcing, simulated Greenland annual temperature anomaly, and moraine records.Upper panel: Northern Hemisphere volcanic sulfate fluxes 5 year running mean; red after ref. 22; black after sup ref 51 (extended data Table S5). Middle panel: Red, PMIP-3 ensemble mean temperature over Greenland (65–15° W, 60–83° N) (extended Table S5); CCSM4 = blue; Fgoals = pink; IPSL = green; GISS = black: MPI = grey BCC = orange. Anomalies are with respect to the 1000–1850 CE period. Lower panel: Red circles are the moraine record at Disko; Black circles are the moraine record in Baffin Bay19. Error bars are moraine age uncertainties related to standard deviation, analytical and production rate uncertainties. The figure was generated with Grapher 11, Golden Software. www.goldensoftxware.com.
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f3: Volcanic forcing, simulated Greenland annual temperature anomaly, and moraine records.Upper panel: Northern Hemisphere volcanic sulfate fluxes 5 year running mean; red after ref. 22; black after sup ref 51 (extended data Table S5). Middle panel: Red, PMIP-3 ensemble mean temperature over Greenland (65–15° W, 60–83° N) (extended Table S5); CCSM4 = blue; Fgoals = pink; IPSL = green; GISS = black: MPI = grey BCC = orange. Anomalies are with respect to the 1000–1850 CE period. Lower panel: Red circles are the moraine record at Disko; Black circles are the moraine record in Baffin Bay19. Error bars are moraine age uncertainties related to standard deviation, analytical and production rate uncertainties. The figure was generated with Grapher 11, Golden Software. www.goldensoftxware.com.

Mentions: However, exploring the synchronicity of external forcings and the Disko moraine record, we show a good correspondence between both records, suggesting that internal variability is combined with other factors. Indeed, we show that M2 (~1200 CE) is contemporaneous with a 50-year period of high volcanic activity with repeated large eruptions, including the 1257 Samalas event (Fig. 2). M3 (~1450 CE) is concomitant with both a major nameless volcanic eruption (1458 CE) and the Spörer Minimum. By contrast, M4 formed towards the end of the LIA (~1720 CE), is associated with low volcanic activity (Fig. 2), but may correspond to the Maunder Minimum (1645–1715 CE). MCA moraines from Baffin Bay19 are also associated with the Oort Minimum and with a cluster of several successive volcanic eruptions in the first two centuries of the last millennium (Figs 2 and 3). LIA moraines also coincide with volcanic eruptions or solar minima, except for a moraine deposited in 1570 ± 20 yr CE.


Paradoxical cold conditions during the medieval climate anomaly in the Western Arctic
Volcanic forcing, simulated Greenland annual temperature anomaly, and moraine records.Upper panel: Northern Hemisphere volcanic sulfate fluxes 5 year running mean; red after ref. 22; black after sup ref 51 (extended data Table S5). Middle panel: Red, PMIP-3 ensemble mean temperature over Greenland (65–15° W, 60–83° N) (extended Table S5); CCSM4 = blue; Fgoals = pink; IPSL = green; GISS = black: MPI = grey BCC = orange. Anomalies are with respect to the 1000–1850 CE period. Lower panel: Red circles are the moraine record at Disko; Black circles are the moraine record in Baffin Bay19. Error bars are moraine age uncertainties related to standard deviation, analytical and production rate uncertainties. The figure was generated with Grapher 11, Golden Software. www.goldensoftxware.com.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: Volcanic forcing, simulated Greenland annual temperature anomaly, and moraine records.Upper panel: Northern Hemisphere volcanic sulfate fluxes 5 year running mean; red after ref. 22; black after sup ref 51 (extended data Table S5). Middle panel: Red, PMIP-3 ensemble mean temperature over Greenland (65–15° W, 60–83° N) (extended Table S5); CCSM4 = blue; Fgoals = pink; IPSL = green; GISS = black: MPI = grey BCC = orange. Anomalies are with respect to the 1000–1850 CE period. Lower panel: Red circles are the moraine record at Disko; Black circles are the moraine record in Baffin Bay19. Error bars are moraine age uncertainties related to standard deviation, analytical and production rate uncertainties. The figure was generated with Grapher 11, Golden Software. www.goldensoftxware.com.
Mentions: However, exploring the synchronicity of external forcings and the Disko moraine record, we show a good correspondence between both records, suggesting that internal variability is combined with other factors. Indeed, we show that M2 (~1200 CE) is contemporaneous with a 50-year period of high volcanic activity with repeated large eruptions, including the 1257 Samalas event (Fig. 2). M3 (~1450 CE) is concomitant with both a major nameless volcanic eruption (1458 CE) and the Spörer Minimum. By contrast, M4 formed towards the end of the LIA (~1720 CE), is associated with low volcanic activity (Fig. 2), but may correspond to the Maunder Minimum (1645–1715 CE). MCA moraines from Baffin Bay19 are also associated with the Oort Minimum and with a cluster of several successive volcanic eruptions in the first two centuries of the last millennium (Figs 2 and 3). LIA moraines also coincide with volcanic eruptions or solar minima, except for a moraine deposited in 1570 ± 20 yr CE.

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.


Related in: MedlinePlus