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 Modelled ice-sheet margins of three Greenland ice-sheet models compared with a geological record from ice-marginal deposits in central West Greenland

1996 ◽  
Vol 23 ◽  
pp. 52-58 ◽  
Author(s):  
Frank G. M. Van Tatenhove ◽  
Adeline Fabre ◽  
Ralf Greve ◽  
Philippe Huybrechts
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Test Material ◽  
Morphological Evidence ◽  
Test Model ◽  
Geological Record ◽  
The Holocene ◽  
West Greenland ◽  
Holocene Climatic Optimum ◽  
Climatic Optimum

Ice-sheet modelling is an essential tool for estimating the effect of climate change on the Greenland ice sheet. The large spatial and long-term temporal scales of the ice-sheet model limits the amount of data which can be used to test model results. The geological record is useful because it provides test material on the time-scales typical for the memory of ice sheets (millennia). This paper compares modelled ice-margin positions with a geological scenario of ice-margin positions since the Last Glacial Maximum to the present in West Greenland. Morphological evidence of ice-margin positions is provided by moraines. Moraine systems are dated by 14C-dated marine shells and terrestrial peat. Three Greenland ice-sheet models are compared. There are distinct differences in modelled ice-margin positions between the models and between model results and the geological record. Disagreement between models and the geological record in the near-coastal area is explained by the inadequate treatment of marginal processes in a tide-water environment. A smaller than present ice sheet around the warm period in the Holocene (Holocene climatic optimum) only occurs if such a period appears in the forcing (ice-core record) or used temporal resolution. Smoothing of the GRIP record with a 2000 year average eliminates the climatic signal related to the Holocene climatic optimum. This underlines the importance of short-term and medium-term variations (decades, centuries) in climatic variables in determining ice-margin positions in the past but also in the future.

scholarly journals High Arctic Holocene temperature record from the Agassiz ice cap and Greenland ice sheet evolution

2017 ◽  
Vol 114 (23) ◽  
pp. 5952-5957 ◽  
Author(s):  
Benoit S. Lecavalier ◽  
David A. Fisher ◽  
Glenn A. Milne ◽  
Bo M. Vinther ◽  
Lev Tarasov ◽  
...  
Keyword(s):  
Air Temperature ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Temperature Reconstruction ◽  
High Arctic ◽  
Early Holocene ◽  
Temperature Record ◽  
The Past ◽  
Ice Cap

We present a revised and extended high Arctic air temperature reconstruction from a single proxy that spans the past ∼12,000 y (up to 2009 CE). Our reconstruction from the Agassiz ice cap (Ellesmere Island, Canada) indicates an earlier and warmer Holocene thermal maximum with early Holocene temperatures that are 4–5 °C warmer compared with a previous reconstruction, and regularly exceed contemporary values for a period of ∼3,000 y. Our results show that air temperatures in this region are now at their warmest in the past 6,800–7,800 y, and that the recent rate of temperature change is unprecedented over the entire Holocene. The warmer early Holocene inferred from the Agassiz ice core leads to an estimated ∼1 km of ice thinning in northwest Greenland during the early Holocene using the Camp Century ice core. Ice modeling results show that this large thinning is consistent with our air temperature reconstruction. The modeling results also demonstrate the broader significance of the enhanced warming, with a retreat of the northern ice margin behind its present position in the mid Holocene and a ∼25% increase in total Greenland ice sheet mass loss (∼1.4 m sea-level equivalent) during the last deglaciation, both of which have implications for interpreting geodetic measurements of land uplift and gravity changes in northern Greenland.

scholarly journals Modelled ice-sheet margins of three Greenland ice-sheet models compared with a geological record from ice-marginal deposits in central West Greenland

1996 ◽  
Vol 23 ◽  
pp. 52-58 ◽  
Author(s):  
Frank G. M. Van Tatenhove ◽  
Adeline Fabre ◽  
Ralf Greve ◽  
Philippe Huybrechts
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Test Material ◽  
Morphological Evidence ◽  
Test Model ◽  
Geological Record ◽  
The Holocene ◽  
West Greenland ◽  
Holocene Climatic Optimum ◽  
Climatic Optimum

Ice-sheet modelling is an essential tool for estimating the effect of climate change on the Greenland ice sheet. The large spatial and long-term temporal scales of the ice-sheet model limits the amount of data which can be used to test model results. The geological record is useful because it provides test material on the time-scales typical for the memory of ice sheets (millennia). This paper compares modelled ice-margin positions with a geological scenario of ice-margin positions since the Last Glacial Maximum to the present in West Greenland. Morphological evidence of ice-margin positions is provided by moraines. Moraine systems are dated by 14C-dated marine shells and terrestrial peat. Three Greenland ice-sheet models are compared. There are distinct differences in modelled ice-margin positions between the models and between model results and the geological record. Disagreement between models and the geological record in the near-coastal area is explained by the inadequate treatment of marginal processes in a tide-water environment. A smaller than present ice sheet around the warm period in the Holocene (Holocene climatic optimum) only occurs if such a period appears in the forcing (ice-core record) or used temporal resolution. Smoothing of the GRIP record with a 2000 year average eliminates the climatic signal related to the Holocene climatic optimum. This underlines the importance of short-term and medium-term variations (decades, centuries) in climatic variables in determining ice-margin positions in the past but also in the future.

scholarly journals Pronounced summer warming in northwest Greenland during the Holocene and Last Interglacial

2018 ◽  
Vol 115 (25) ◽  
pp. 6357-6362 ◽  
Author(s):  
Jamie M. McFarlin ◽  
Yarrow Axford ◽  
Magdalena R. Osburn ◽  
Meredith A. Kelly ◽  
Erich C. Osterberg ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Holocene ◽  
Last Interglacial ◽  
Last Glacial Period ◽  
The Holocene ◽  
Sedimentary Records ◽  
Paleoclimate Records ◽  
The Last Glacial

Projections of future rates of mass loss from the Greenland Ice Sheet are highly uncertain because its sensitivity to warming is unclear. Geologic reconstructions of Quaternary interglacials can illustrate how the ice sheet responded during past warm periods, providing insights into ice sheet behavior and important tests for data-model comparisons. However, paleoclimate records from Greenland are limited: Early Holocene peak warmth has been quantified at only a few sites, and terrestrial sedimentary records of prior interglacials are exceptionally rare due to glacial erosion during the last glacial period. Here, we discuss findings from a lacustrine archive that records both the Holocene and the Last Interglacial (LIG) from Greenland, allowing for direct comparison between two interglacials. Sedimentary chironomid assemblages indicate peak July temperatures 4.0 to 7.0 °C warmer than modern during the Early Holocene maximum in summer insolation. Chaoborus and chironomids in LIG sediments indicate July temperatures at least 5.5 to 8.5 °C warmer than modern. These estimates indicate pronounced warming in northwest Greenland during both interglacials. This helps explain dramatic ice sheet thinning at Camp Century in northwest Greenland during the Early Holocene and, for the LIG, aligns with controversial estimates of Eemian warming from ice core data retrieved in northern Greenland. Converging geologic evidence for strong LIG warming is challenging to reconcile with inferred Greenland Ice Sheet extent during the LIG, and the two appear incompatible in many models of ice sheet evolution. An increase in LIG snowfall could help resolve this problem, pointing to the need for hydroclimate reconstructions from the region.

scholarly journals The Holocene thermal maximum in the Nordic Seas: the impact of Greenland Ice Sheet melt and other forcings in a coupled atmosphere–sea-ice–ocean model

2013 ◽  
Vol 9 (4) ◽  
pp. 1629-1643 ◽  
Author(s):  
M. Blaschek ◽  
H. Renssen
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Holocene ◽  
Surface Cooling ◽  
Holocene Climate ◽  
Nordic Seas ◽  
The Holocene ◽  
Holocene Thermal Maximum ◽  
Thermal Maximum ◽  
The Impact

Abstract. The relatively warm early Holocene climate in the Nordic Seas, known as the Holocene thermal maximum (HTM), is often associated with an orbitally forced summer insolation maximum at 10 ka BP. The spatial and temporal response recorded in proxy data in the North Atlantic and the Nordic Seas reveals a complex interaction of mechanisms active in the HTM. Previous studies have investigated the impact of the Laurentide Ice Sheet (LIS), as a remnant from the previous glacial period, altering climate conditions with a continuous supply of melt water to the Labrador Sea and adjacent seas and with a downwind cooling effect from the remnant LIS. In our present work we extend this approach by investigating the impact of the Greenland Ice Sheet (GIS) on the early Holocene climate and the HTM. Reconstructions suggest melt rates of 13 mSv for 9 ka BP, which result in our model in an ocean surface cooling of up to 2 K near Greenland. Reconstructed summer SST gradients agree best with our simulation including GIS melt, confirming that the impact of the early Holocene GIS is crucial for understanding the HTM characteristics in the Nordic Seas area. This implies that modern and near-future GIS melt can be expected to play an active role in the climate system in the centuries to come.

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 Holocene thermal maximum in the Nordic Seas: the impact of Greenland Ice Sheet melt and other forcings in a coupled atmosphere-sea ice-ocean model

2012 ◽  
Vol 8 (5) ◽  
pp. 5263-5291 ◽  
Author(s):  
M. Blaschek ◽  
H. Renssen
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Holocene ◽  
Surface Cooling ◽  
Holocene Climate ◽  
Nordic Seas ◽  
The Holocene ◽  
Holocene Thermal Maximum ◽  
Thermal Maximum ◽  
The Impact

Abstract. The relatively warm early Holocene climate in the Nordic Seas, known as the Holocene Thermal Maximum (HTM), is often associated with an orbitally forced summer insolation maximum at 10 ka BP. The spatial and temporal response recorded in proxy data in the North Atlantic and the Nordic Seas reveal a complex interaction of mechanisms active in the HTM. Previous studies have investigated the impact of the Laurentide Ice Sheet (LIS), as a remnant from a previous glacial period, altering climate conditions with a continuous supply of melt water to the Labrador Sea and adjacent seas and with a downwind cooling effect from the remnant LIS. In our present work we extend this approach by investigating the impact of the Greenland Ice Sheet (GIS) on the early Holocene climate and the HTM. Reconstructions suggest melt rates of 13 mSv for 9 ka BP, which result in our model in a ocean surface cooling of up to 2 K near Greenland. Reconstructed summer SST gradients agree best with our simulation including GIS melt, confirming that the impact of early Holocene GIS is crucial for understanding the HTM characteristics in the Nordic Seas area. This implies that the modern and near-future GIS melt can be expected to play an active role in the climate system in the centuries to come.

scholarly journals The Holocene dynamics of Ryder Glacier and ice tongue in north Greenland

2021 ◽  
Vol 15 (8) ◽  
pp. 4073-4097
Author(s):  
Matt O'Regan ◽  
Thomas M. Cronin ◽  
Brendan Reilly ◽  
Aage Kristian Olsen Alstrup ◽  
Laura Gemery ◽  
...  
Keyword(s):  
Climate Change ◽  
Late Holocene ◽  
Sediment Cores ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Sedimentary Facies ◽  
Climate Forcing ◽  
The Holocene ◽  
Middle Holocene ◽  
Vulnerability To Climate Change

Abstract. The northern sector of the Greenland Ice Sheet is considered to be particularly susceptible to ice mass loss arising from increased glacier discharge in the coming decades. However, the past extent and dynamics of outlet glaciers in this region, and hence their vulnerability to climate change, are poorly documented. In the summer of 2019, the Swedish icebreaker Oden entered the previously unchartered waters of Sherard Osborn Fjord, where Ryder Glacier drains approximately 2 % of Greenland's ice sheet into the Lincoln Sea. Here we reconstruct the Holocene dynamics of Ryder Glacier and its ice tongue by combining radiocarbon dating with sedimentary facies analyses along a 45 km transect of marine sediment cores collected between the modern ice tongue margin and the mouth of the fjord. The results illustrate that Ryder Glacier retreated from a grounded position at the fjord mouth during the Early Holocene (> 10.7±0.4 ka cal BP) and receded more than 120 km to the end of Sherard Osborn Fjord by the Middle Holocene (6.3±0.3 ka cal BP), likely becoming completely land-based. A re-advance of Ryder Glacier occurred in the Late Holocene, becoming marine-based around 3.9±0.4 ka cal BP. An ice tongue, similar in extent to its current position was established in the Late Holocene (between 3.6±0.4 and 2.9±0.4 ka cal BP) and extended to its maximum historical position near the fjord mouth around 0.9±0.3 ka cal BP. Laminated, clast-poor sediments were deposited during the entire retreat and regrowth phases, suggesting the persistence of an ice tongue that only collapsed when the glacier retreated behind a prominent topographic high at the landward end of the fjord. Sherard Osborn Fjord narrows inland, is constrained by steep-sided cliffs, contains a number of bathymetric pinning points that also shield the modern ice tongue and grounding zone from warm Atlantic waters, and has a shallowing inland sub-ice topography. These features are conducive to glacier stability and can explain the persistence of Ryder's ice tongue while the glacier remained marine-based. However, the physiography of the fjord did not halt the dramatic retreat of Ryder Glacier under the relatively mild changes in climate forcing during the Holocene. Presently, Ryder Glacier is grounded more than 40 km seaward of its inferred position during the Middle Holocene, highlighting the potential for substantial retreat in response to ongoing climate change.

scholarly journals Tracing the depth of the Holocene ice in North Greenland from radio-echo sounding data

2013 ◽  
Vol 54 (64) ◽  
pp. 44-50 ◽  
Author(s):  
Nanna B. Karlsson ◽  
Dorthe Dahl-Jensen ◽  
S. Prasad Gogineni ◽  
John D. Paden
Keyword(s):  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
The Holocene ◽  
Fitting Method ◽  
Radio Echo Sounding ◽  
North Greenland ◽  
Echo Sounding

Abstract Radio-echo sounding surveys over the Greenland ice sheet show clear, extensive internal layering, and comparisons with age–depth scales from deep ice cores allow for dating of the layering along the ice divide. We present one of the first attempts to extend the dated layers beyond the ice core drill sites by locating the depth of the Bølling–Allerød transition in >400 flight-lines using an automated fitting method. Results show that the transition is located in the upper one-third of the ice column in the central part of North Greenland, while the transition lowers towards the margin. This pattern mirrors the present surface accumulation, and also indicates that a substantial amount of pre-Holocene ice must be present in central North Greenland.

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