Late-Holocene North Atlantic climate ‘seesaws’,                 storminess changes and Greenland ice sheet (GISP2) palaeoclimates

The observational record of ice margin position reveals asynchrony in both the timing and magnitude of Greenland Ice Sheet (GrIS) margin fluctuations and illustrates the complex reactions of ice sheets to climatic perturbations. In this study, we reconstruct the timing and pattern of middle- and late-Holocene GrIS margin fluctuations at two locations, ~190 km apart, in central West Greenland using radiocarbon-dated sediment cores from proglacial-threshold lakes. Our results demonstrate that deglaciation occurs at both sites during the early Holocene, with the ice sheet remaining in a smaller-than-present ice margin configuration until ~500 years ago when it readvanced into lake catchments at both sites. At our northern site, Sermeq Kujatdleq, the late-Holocene advance of the GrIS approached maximum position during the past 280 years, with the culmination of the advance occurring at AD 1992–1994, and modern retreat was underway by AD 1998–2001. In contrast, field and observational evidence suggest that the GrIS at our southern site, Nordenskiöld Gletscher, has been advancing or stable throughout the 20th century. These results, in conjunction with previous work in the region, highlight the asynchronous nature of late-Holocene advances and subsequent modern retreat, implying that local variability, such as ice velocity or ice dynamics, is responsible for modulating ice margin response to changes in climate on these decadal to centennial timescales. Additional high-resolution records of past ice sheet fluctuations are needed to inform and more accurately constrain our predictions of future cryosphere response to changes in climate.

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Greenland melting signatures in model simulations and oceanic observations

10.5194/egusphere-egu21-8225 ◽

2021 ◽

Author(s):

Sophie Stolzenberger ◽

Roelof Rietbroek ◽

Claudia Wekerle ◽

Bernd Uebbing ◽

Jürgen Kusche

Keyword(s):

North Atlantic ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ocean Model ◽

Freshwater Flux ◽

Model Simulations ◽

The North ◽

Sea Level Anomalies ◽

The North Atlantic ◽

The Impact

<p>The impact of Greenland freshwater on oceanic variables in the North Atlantic has been controversially discussed in the past. Within the framework of the German research project GROCE (Greenland Ice Sheet Ocean Interaction), we present a comprehensive study using ocean modelling results including and excluding the Greenland freshwater flux. The aim of this study is whether signatures of Greenland ice sheet melting found in ocean model simulations are visible in the observations. Therefore, we estimate changes in temperature, salinity, steric heights and sea level anomalies since the 1990s. The observational database includes altimetric and gravimetric satellite data as well as Argo floats. We will discuss similarities/differences between model simulations and observations for smaller regions around Greenland in the North Atlantic. As these experiments are available for two different horizontal resolutions, we will furthermore be able to assess the effects of an increased model resolution.</p>

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On the role of atmospheric feedbacks in sustaining the anomalous warmth of the MIS-11 interglacial

10.5194/egusphere-egu21-7316 ◽

2021 ◽

Author(s):

Brian Crow ◽

Matthias Prange ◽

Michael Schulz

Keyword(s):

North Atlantic ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Meridional Overturning Circulation ◽

Interglacial Period ◽

Climate Modelling ◽

Ice Dynamics ◽

The North ◽

Atmospheric Feedbacks ◽

The North Atlantic

<p>Historical estimates of the melt rate and extent of the Greenland ice sheet (GrIS) are poorly constrained, due both to incomplete understanding of relevant ice dynamics and the magnitude of forcing acting upon the ice sheet (e.g., Alley et al. 2010). Previous assessments of the Marine Isotope Stage 11 (MIS-11) interglacial period have determined it was likely one of the warmest and longest interglacial periods of the past 800 kyr, leading to melt of at least half the present-day volume of the Greenland ice sheet (Robinson et al. 2017). An enhanced Atlantic meridional overturning circulation (AMOC) is commonly cited as sustaining the anomalous warmth across the North Atlantic and Greenland (e.g., Rachmayani et al. 2017), but little is known about potential atmospheric contributions. Paleorecords from this period are sparse, and detailed climate modelling studies of this period have been heretofore very limited. The climatic conditions over Greenland and the North Atlantic region, and how they may have contributed to the melt of the GrIS during MIS-11, are therefore not well understood. By utilizing climate simulations with the Community Earth System Model (CESM), our study indicates that changes in atmospheric eddy behavior, including eddy fluxes of heat and precipitation, made significant contributions to the negative mass balance conditions over the GrIS during the MIS-11 interglacial. Thus, accounting for the effects of atmospheric feedbacks in a warmer-than-present climate is a necessary component for future analyses attempting to better constrain the extent and rate of melt of the GrIS.</p>

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Middle to late Holocene chronology of the western margin of the Greenland Ice Sheet: A comparison with Holocene temperature and precipitation records

Arctic Antarctic and Alpine Research ◽

10.1080/15230430.2017.1414477 ◽

2018 ◽

Vol 50 (1) ◽

pp. S100004 ◽

Cited By ~ 4

Author(s):

Laura B. Levy ◽

Meredith A. Kelly ◽

Patrick A. Applegate ◽

Jennifer A. Howley ◽

Ross A. Virginia

Keyword(s):

Late Holocene ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Western Margin ◽

Temperature And Precipitation ◽

Precipitation Records

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Accelerated mass loss from Greenland ice sheet: Links to atmospheric circulation in the North Atlantic

Global and Planetary Change ◽

10.1016/j.gloplacha.2015.02.006 ◽

2015 ◽

Vol 128 ◽

pp. 61-71 ◽

Cited By ~ 15

Author(s):

Ki-Weon Seo ◽

Duane E. Waliser ◽

Choon-Ki Lee ◽

Baijun Tian ◽

Ted Scambos ◽

...

Keyword(s):

Mass Loss ◽

Atmospheric Circulation ◽

North Atlantic ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

The North ◽

The North Atlantic

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The Occurrence and Properties of Long-Lived Liquid-Bearing Clouds over the Greenland Ice Sheet and Their Relationship to the North Atlantic Oscillation

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-17-0230.1 ◽

2018 ◽

Vol 57 (4) ◽

pp. 921-935 ◽

Cited By ~ 4

Author(s):

Jonathan Edwards-Opperman ◽

Steven Cavallo ◽

David Turner

Keyword(s):

North Atlantic Oscillation ◽

North Atlantic ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

The Arctic ◽

Positive Phase ◽

Cloud Base ◽

The North ◽

The North Atlantic ◽

The North Atlantic Oscillation

AbstractStratiform liquid-bearing clouds (LBCs), defined herein as either pure liquid or mixed-phase clouds, have a large impact on the surface radiation budget across the Arctic. LBCs lasting at least 6 h are observed at Summit, Greenland, year-round with a maximum in occurrence during summer. Mean cloud-base height is below 1 km for 85% of LBC cases identified, 59% have mean liquid water path (LWP) values between 10 and 40 g m−2, and most produce sporadic light ice-phase precipitation. During their occurrence, the atmosphere above the ice sheet is anomalously warm and moist, with southerly winds observed over much of the ice sheet, including at Summit. LBCs that occur when the North Atlantic Oscillation (NAO) is in the negative phase correspond to strong ridging centered over the Greenland Ice Sheet (GIS), allowing for southwesterly flow over the GIS toward Summit. During the positive phase of the NAO, the occurrence of LBCs corresponds to a cyclone located off the southeastern coast of the ice sheet, which leads to easterly-to-southeasterly flow toward Summit. Furthermore, air parcels at Summit frequently originate from below the elevation of Summit, indicating that orographic lift along the ice sheet is a factor in the occurrence of LBCs at Summit. LBCs are more frequently observed during the negative NAO, and both the LWP and precipitation rate are larger in LBCs occurring during this phase. Mean LWP in LBCs occurring during the negative NAO is 15 g m−2 larger than in LBCs occurring during the positive phase.

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Small impact of surrounding oceanic conditions on 2007–2012 Greenland Ice Sheet surface mass balance

The Cryosphere Discussions ◽

10.5194/tcd-8-1453-2014 ◽

2014 ◽

Vol 8 (2) ◽

pp. 1453-1477 ◽

Cited By ~ 2

Author(s):

B. Noël ◽

X. Fettweis ◽

W. J. van de Berg ◽

M. R. van den Broeke ◽

M. Erpicum

Keyword(s):

Mass Balance ◽

North Atlantic ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Surface Mass Balance ◽

Katabatic Winds ◽

Surface Mass ◽

The North ◽

The North Atlantic ◽

Surface Melt

Abstract. During recent summers (2007–2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North-Atlantic Oscillation (NAO), favouring warmer than normal conditions over the GrIS. In addition, it has been suggested that significant anomalies in sea ice cover (SIC) and sea surface temperature (SST) may partially explain recent anomalous GrIS surface melt. To assess the impact of 2007–2012 SIC and SST anomalies on GrIS surface mass balance (SMB), a set of sensitivity experiments was carried out with the regional climate model MAR. These simulations suggest that changes in SST and SIC in the seas surrounding Greenland do not significantly impact GrIS SMB, due to the katabatic winds blocking effect. These winds are strong enough to prevent oceanic near-surface air, influenced by SIC and SST variability, from penetrating far inland. Therefore, the ice sheet SMB response is restricted to coastal regions, where katabatic winds are weaker. However, anomalies in SIC and SST could have indirectly affected the surface melt by changing the general circulation in the North Atlantic region, favouring more frequent warm air advection to the GrIS.

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

The Cryosphere ◽

10.5194/tc-15-4073-2021 ◽

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.

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