scholarly journals Melt in the Greenland EastGRIP ice core reveals Holocene warming events

2021 ◽  
Author(s):  
Julien Westhoff ◽  
Giulia Sinnl ◽  
Anders Svensson ◽  
Johannes Freitag ◽  
Helle Astrid Kjær ◽  
...  
Keyword(s):  
Tree Ring ◽  
Ice Core ◽  
Dark Field ◽  
Ice Age ◽  
Rain Event ◽  
The Holocene ◽  
Holocene Climatic Optimum ◽  
Melt Infiltration ◽  
Brittle Zone ◽  
Climatic Optimum

Abstract. We present a record of melt events obtained from the EastGRIP ice core, in central north eastern Greenland, covering the largest part of the Holocene. The data were acquired visually using an optical dark-field line scanner. We detect and describe bubble free layers and -lenses throughout the ice above the bubble-clathrate transition, located at 1100 m in the EastGRIP ice core, corresponding to an age of 9720 years b2k. We distinguish between melt layers (bubble free layers continuous over the width of the core), melt lenses (discontinuous), crusts (thin and sharp bubble free layers) and attribute three levels of confidence to each of these, depending on how clearly they are identified. 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. We analyze melt layer thicknesses and correct for ice thinning, we account for missing layers due to core breaks, and ignore layers thinner than 1.5 mm. We define the brittle zone in the EastGRIP ice core from 650 m to 950 m depth, where we count on average more than three core breaks per meter. In total we can identify approximately 831 mm of melt (corrected for thinning) over the past 10,000 years. We compare our melt layer record to the GISP2 and Renland melt layer records. Our climatic interpretation matches well with the Little Ice Age, the Medieval and Roman Warm Periods, the Holocene Climatic Optimum, and the 8.2 kyr event. 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. We open the discussion for sloping bubble free layers (tilt angle off horizontal > 10°) being the effect of rheology and not climate. We also discuss our melt layers in connection to a coffee experiment (coffee as a colored substitute for melt infiltration into the snow pack) and the real time observations of the 2012 CE rain event at NEEM. We find that the melt event from 986 CE is most likely a large rain event, similar to 2012 CE, and that these two events are unprecedented throughout the Holocene. Furthermore, we suggest that the warm summer of 986 CE, with the exceptional melt event, was the trigger for the first Viking voyages to sail from Iceland to Greenland.

Recently exposed subglacial carbonate deposits at the retreating Triglav Glacier, Slovenia

2020 ◽  
Author(s):  
Matej Lipar ◽  
Andrea Martín Pérez ◽  
Jure Tičar ◽  
Miha Pavšek ◽  
Matej Gabrovec ◽  
...  
Keyword(s):  
Middle Ages ◽  
Extreme Values ◽  
Ice Age ◽  
Temperate Climate ◽  
The Holocene ◽  
The Past ◽  
Holocene Climatic Optimum ◽  
Frost Weathering ◽  
Climatic Optimum ◽  
Carbonate Deposits

<p>Subglacial carbonate deposits have been exposed on the lee sides of small protuberances on a bare polished and striated limestone bedrock surface in the immediate vicinity of the retreating Triglav Glacier in southeastern Alps. They are fluted and furrowed crust-like deposits generally around 5 mm thick and characterized by brownish, greyish or yellowish colour. The deposits are generally around 0.5 cm in thickness and internally laminated. They offer a unique opportunity to gain additional knowledge of the past glacier’s behaviour and consequently the characteristics of the past climate which is essential to understand and predict future changes. Currently, the known extent and behaviour of the Triglav Glacier spans from the present to the Little Ice Age, the cool-climate anomaly between the Late Middle Ages and the mid-19th century, and is based on geomorphological remnants, historical records, and systematic monitoring. However, the preliminary uranium-thorium (U-Th) ages of the subglacial carbonates yielded considerably old ages: 23.62 ka ± 0.78 ka, 18.45 ka ± 0.70 ka and 12.72 ka ± 0.28 ka; the results indicate that these subglacial carbonate dates fall within the Last Glacial Maximum (LGM) and the Younger Dryas (YD).</p><p>The Triglav Glacier has generally been viewed as relict of the LIA, with discontinuous presence due to the Holocene Climatic Optimum, a period of high insolation and generally warmer climate between 11,000 and 5,000 years BP. Present chemical denudation rates of carbonate rocks in Alpine and temperate climate vary from ca. 0.009 to 0.140 mm/year. Taking the low and high extreme values for, e.g., 6 ka during the Holocene Climatic Optimum, the denudation in the Triglav area would be between 54 and 840 mm, so the exposed 5 mm thick subglacial carbonate would have already been denuded if exposed in the past. In addition, carbonate surfaces in periglacial areas are additionally exposed to frost weathering, promoting disintegration of depositional features. And lastly, glaciers cause pronounced erosion and in case of just a short-term retreat beyond the subglacial carbonates, the re-advance of the glacier would likely abrade the deposits. Therefore, had the subglacial carbonate deposits been exposed in the past, they should have been eroded by chemical denudation, frost weathering, or erosion at the onset of individual Holocene glacial expansion episodes, such as the LIA. May the presence of subglacial carbonates dated to the LGM and the YD at the Triglav Glacier suggest the continuous existence of the glacier throughout all but the latest Holocene?</p>

scholarly journals A Holocene black carbon ice-core record of biomass burning in the Amazon Basin from Illimani, Bolivia

2018 ◽  
Author(s):  
Dimitri Osmont ◽  
Michael Sigl ◽  
Anja Eichler ◽  
Theo M. Jenk ◽  
Margit Schwikowski
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Amazon Basin ◽  
Ice Core ◽  
Medieval Warm Period ◽  
Warm Period ◽  
The Holocene ◽  
Holocene Climatic Optimum ◽  
Ice Core Record ◽  
Climatic Optimum

Abstract. The Amazon Basin is one of the major contributors to global biomass burning emissions. However, regional paleofire trends remain partially unknown. Due to their proximity to the Amazon Basin, Andean ice cores are suitable to reconstruct paleofire trends in South America and improve our understanding of the complex linkages between fires, climate and humans. Here we present the first refractory black carbon (rBC) ice-core record from the Andes as a proxy for biomass burning emissions in the Amazon Basin, derived from an ice core drilled at 6300 m a.s.l. from Illimani glacier in the Bolivian Andes and spanning the entire Holocene back to the last deglaciation 13 000 years ago. The Illimani rBC record displays a strong seasonality with low values during the wet season and high values during the dry season due to the combination of enhanced biomass burning emissions in the Amazon Basin and less precipitation at the Illimani site. Significant positive (negative) correlations were found with reanalyzed temperature (precipitation) data, respectively, for regions in Eastern Bolivia and Western Brazil characterized by a substantial fire activity. rBC long-term trends indirectly reflect regional climatic variations through changing biomass burning emissions as they show higher (lower) concentrations during warm/dry (cold/wet) periods, respectively, in line with climate variations such as the Younger Dryas, the 8.2 ka event, the Holocene Climatic Optimum, the Medieval Warm Period or the Little Ice Age. The highest rBC concentrations of the entire record occurred during the Holocene Climatic Optimum between 7000 and 3000 BC, suggesting that this outstanding warm and dry period caused an exceptional biomass burning activity, unprecedented in the context of the past 13 000 years. Recent rBC levels, rising since 1730 AD in the context of increasing temperatures and deforestation, are similar to those of the Medieval Warm Period. No decrease was observed in the 20th century, in contradiction with the global picture (broken fire hockey stick hypothesis).

scholarly journals The effect of a Holocene climatic optimum on the evolution of the Greenland ice sheet during the last 10 kyr

2018 ◽  
Vol 64 (245) ◽  
pp. 477-488 ◽  
Author(s):  
LISBETH T. NIELSEN ◽  
GUðFINNA AÐALGEIRSDÓTTIR ◽  
VASILEIOS GKINIS ◽  
ROMAN NUTERMAN ◽  
CHRISTINE S. HVIDBERG
Keyword(s):  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Holocene ◽  
Climate Forcing ◽  
The Holocene ◽  
The Past ◽  
Holocene Climatic Optimum ◽  
Surface Temperatures ◽  
Climatic Optimum

ABSTRACTThe Holocene climatic optimum was a period 8–5 kyr ago when annual mean surface temperatures in Greenland were 2–3°C warmer than present-day values. However, this warming left little imprint on commonly used temperature proxies often used to derive the climate forcing for simulations of the past evolution of the Greenland ice sheet. In this study, we investigate the evolution of the Greenland ice sheet through the Holocene when forced by different proxy-derived temperature histories from ice core records, focusing on the effect of sustained higher surface temperatures during the early Holocene. We find that the ice sheet retreats to a minimum volume of ~0.15–1.2 m sea-level equivalent smaller than present in the early or mid-Holocene when forcing an ice-sheet model with temperature reconstructions that contain a climatic optimum, and that the ice sheet has continued to recover from this minimum up to present day. Reconstructions without a warm climatic optimum in the early Holocene result in smaller ice losses continuing throughout the last 10 kyr. For all the simulated ice-sheet histories, the ice sheet is approaching a steady state at the end of the 20th century.

scholarly journals Tree-ring radiocarbon reveals reduced solar activity during Younger Dryas cooling

2020 ◽  
Author(s):  
Adam Sookdeo ◽  
Bernd Kromer ◽  
Florian Adolphi ◽  
Jürg Beer ◽  
Nicolas Brehm ◽  
...  
Keyword(s):  
Solar Activity ◽  
Tree Ring ◽  
North Atlantic ◽  
Little Ice Age ◽  
Ice Core ◽  
Younger Dryas ◽  
Ice Age ◽  
The North ◽  
Long Duration ◽  
Clear Sign

<p>The Younger Dryas stadial (YD) was a return to glacial-like conditions in the North Atlantic region that interrupted deglacial warming around 12900 cal BP (before 1950 AD). Terrestrial and marine records suggest this event was initiated by the interruption of deep-water formation arising from North American freshwater runoff, but the causes of the millennia-long duration remain unclear. To investigate the solar activity, a possible YD driver, we exploit the cosmic production signals of tree-ring radiocarbon (<sup>14</sup>C) and ice-core beryllium-10 (<sup>10</sup>Be). Here we present the highest temporally resolved dataset of <sup>14</sup>C measurements (n = 1558) derived from European tree rings that have been accurately extended back to 14226 cal BP (±8, 2-σ), allowing precise alignment of ice-core records across this period. We identify a substantial increase in <sup>14</sup>C and <sup>10</sup>Be production starting at 12780 cal BP is comparable in magnitude to the historic Little Ice Age, being a clear sign of grand solar minima. We hypothesize the timing of the grand solar minima provides a significant amplifying factor leading to the harsh sustained glacial-like conditions seen in the YD.</p>

High-frequency winter cooling and reef coral mortality during the Holocene climatic optimum

2004 ◽  
Vol 224 (1-2) ◽  
pp. 143-155 ◽  
Author(s):  
Ke-Fu Yu ◽  
Jian-Xin Zhao ◽  
Tung-Sheng Liu ◽  
Gang-Jian Wei ◽  
Pin-Xian Wang ◽  
...  
Keyword(s):  
High Frequency ◽  
Reef Coral ◽  
Coral Mortality ◽  
The Holocene ◽  
Holocene Climatic Optimum ◽  
Climatic Optimum ◽  
Winter Cooling

Florida wildfires during the Holocene Climatic Optimum (9000–5000 cal yr BP)

2018 ◽  
Vol 60 (1) ◽  
pp. 51-66
Author(s):  
Kalindhi Larios Mendieta ◽  
Stefan Gerber ◽  
Mark Brenner
Keyword(s):  
The Holocene ◽  
Holocene Climatic Optimum ◽  
Climatic Optimum

scholarly journals Holocene deglaciation and climate history of the northern Antarctic Peninsula region: a discussion of correlations between the Southern and Northern Hemispheres

1998 ◽  
Vol 27 ◽  
pp. 110-112 ◽  
Author(s):  
Christian Hjort ◽  
Svante Björck ◽  
Ólafur Ingólfsson ◽  
Per Möller
Keyword(s):  
Northern Hemisphere ◽  
Antarctic Peninsula ◽  
Ice Melting ◽  
Climate History ◽  
The Holocene ◽  
Holocene Climatic Optimum ◽  
History Of ◽  
Climatic Optimum ◽  
Insolation Maximum

The chronology of post-Last Glaciol Maximum deglaciation in the northern Antarctic Peninsula region is discussed. It is concluded that, contrary to what was earlier believed, the deglaciation process here was largely out-of-phase with that in the Northern Hemisphere. Although, for global eustatic reasons, the marine-based glaciers may have retreated simultaneously with ice-melting in the Northern Hemisphere, the land-based glaciers retreated only slowly during the first halfoftlie Holocene, about 9000-5000 BP. This may have been due either to increased precipitation counterweighing ablation or to delayed warming. A distinct but rather brief Glaciol readvancc took place around 5000 BP, probably caused by a period of renewed cooling. It was followed by the Holocene climatic optimum, about 4000-3000 BP. This warm “hypsithermal” period thus came much later than its equivalent in the Northern Hemisphere, but it roughly coincided with the Milankovitchcan Holocene insolation maximum for these southern latitudes.

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