A century of climate variability and climate gradients from coast to ice sheet in west greenland

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Brodersen, K. P., & Anderson, N. J. (2000). Subfossil insect remains (Chironomidae) and lake-water temperature inference in the Sisimiut–Kangerlussuaq region, southern West Greenland. Geology of Greenland Survey Bulletin, 186, 78-82. https://doi.org/10.34194/ggub.v186.5219 _______________ Climate and water temperature have an important influence on the functioning of lake ecosystems. From limnological and palaeolimnological studies of lakes, information on biological diversity and climate variability in time and space can be gleaned from physical, chemical and biological indicators preserved in the lake sediments. The lakes in southern West Greenland are particularly useful for this purpose – they are numerous, diverse and have minimal anthropogenic impact (Anderson & Bennike 1997). Palaeolimnological data are fundamental for understanding the functioning and development of modern lakes and for understanding the causes of climatic change as well as the effect on lake biota.

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Natural variability and recent warming in central Greenland ice cores

10.5194/egusphere-egu21-12914 ◽

2021 ◽

Author(s):

Maria Hoerhold ◽

Thomas Münch ◽

Stefanie Weißbach ◽

Sepp Kipfstuhl ◽

Bo Vinther ◽

...

Keyword(s):

Climate Variability ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Cores ◽

Natural Variability ◽

The Arctic ◽

Last Millennium ◽

Recent Warming ◽

Temperature Reconstructions ◽

Firn Core

Climate variability of the Arctic region has been investigated by means of temperature reconstructions based on proxies from various climate archives around the Arctic, compiled over the last 2000a in the so called Arctic2k record. However, the representativeness of the Arctic2k reconstruction for central Greenland remains unclear, since only a few ice cores have been included in the reconstruction, and observations from the Greenland Ice Sheet (GIC) report ambiguous warming trends for the end of the 20th and the beginning of the 21st century which are not displayed by Arctic2k. Today, the GIC experiences periods with temperatures close to or above the freezing point at high elevations, area-wide melting and mass loss. In order to assess the recent warming as signature of global climate change, records of past climate changes with appropriate temporal and spatial coverage can serve as a benchmark for naturally driven climate variability. Instrumental records for Greenland are short and geographically sparse, and existing temperature reconstructions from single ice cores are noisy, leading to an inconclusive assessment of the recent warming for Greenland.Here, we provide a Greenland firn-core stack covering the time span of the last millennium until the first decade of the 21st century in unprecedented quality by re-drilling as well as analyzing 16 existing firn core sites. We find a strong decadal to bi-decadal natural variability in the record, and, while the record exhibits several warming events with trends that show a similar amplitude as the recent one, we find that the recent absolute values of stable oxygen isotope composition are unprecedented for the last 1000 years.&#160;Comparing our Greenland record with the Arctic 2k temperature reconstruction shows that the correlation between the two records changes throughout the last millennium. While in the periods of 1200-1300 and 1400-1650 CE the records correlate positively, between 1300 and 1400 and 1650-1700 CE shorter periods with negative correlation are found. Since then the correlation is characterized by alternation between positive and zero correlation, with a drop towards negative values at the end of the 20th century. Including re-analysis data, we hypothesize that the climate on top of the GIC was decoupled from the surrounding Arctic for the last decades, leading to the observed mismatch in observations of warming trends.We suggest that the recently observed Greenland temperatures are a superposition of a strong natural variability with an anthropogenic long-term trend. Our findings illustrate that global warming has reached the interior of the Greenland ice sheet, which will have implications for its surface mass balance and Greenland&#8217;s future contribution to sea level rise.Our record complements the Arctic 2k record to a profound view on the Arctic climate variability, where regional compilations may not be representative for specific areas.

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A new approach for simulating the paleo-evolution of the Northern Hemisphere ice sheets

Geoscientific Model Development ◽

10.5194/gmd-11-2299-2018 ◽

2018 ◽

Vol 11 (6) ◽

pp. 2299-2314 ◽

Cited By ~ 5

Author(s):

Rubén Banderas ◽

Jorge Alvarez-Solas ◽

Alexander Robinson ◽

Marisa Montoya

Keyword(s):

Climate Variability ◽

Ice Core ◽

Ice Sheets ◽

Ice Sheet ◽

Temperature Reconstruction ◽

Anomaly Field ◽

Temperature Anomalies ◽

Ice Volume ◽

Index Approach ◽

Millennial Scale

Abstract. Offline forcing methods for ice-sheet models often make use of an index approach in which temperature anomalies relative to the present are calculated by combining a simulated glacial–interglacial climatic anomaly field, interpolated through an index derived from the Greenland ice-core temperature reconstruction, with present-day climatologies. An important drawback of this approach is that it clearly misrepresents climate variability at millennial timescales. The reason for this is that the spatial glacial–interglacial anomaly field used is associated with orbital climatic variations, while it is scaled following the characteristic time evolution of the index, which includes orbital and millennial-scale climate variability. The spatial patterns of orbital and millennial variability are clearly not the same, as indicated by a wealth of models and data. As a result, this method can be expected to lead to a misrepresentation of climate variability and thus of the past evolution of Northern Hemisphere (NH) ice sheets. Here we illustrate the problems derived from this approach and propose a new offline climate forcing method that attempts to better represent the characteristic pattern of millennial-scale climate variability by including an additional spatial anomaly field associated with this timescale. To this end, three different synthetic transient forcing climatologies are developed for the past 120 kyr following a perturbative approach and are applied to an ice-sheet model. The impact of the climatologies on the paleo-evolution of the NH ice sheets is evaluated. The first method follows the usual index approach in which temperature anomalies relative to the present are calculated by combining a simulated glacial–interglacial climatic anomaly field, interpolated through an index derived from ice-core data, with present-day climatologies. In the second approach the representation of millennial-scale climate variability is improved by incorporating a simulated stadial–interstadial anomaly field. The third is a refinement of the second one in which the amplitudes of both orbital and millennial-scale variations are tuned to provide perfect agreement with a recently published absolute temperature reconstruction over Greenland. The comparison of the three climate forcing methods highlights the tendency of the usual index approach to overestimate the temperature variability over North America and Eurasia at millennial timescales. This leads to a relatively high NH ice-volume variability on these timescales. Through enhanced ablation, this results in too low an ice volume throughout the last glacial period (LGP), below or at the lower end of the uncertainty range of estimations. Improving the representation of millennial-scale variability alone yields an important increase in ice volume in all NH ice sheets but especially in the Fennoscandian Ice Sheet (FIS). Optimizing the amplitude of the temperature anomalies to match the Greenland reconstruction results in a further increase in the simulated ice-sheet volume throughout the LGP. Our new method provides a more realistic representation of orbital and millennial-scale climate variability and improves the transient forcing of ice sheets during the LGP. Interestingly, our new approach underestimates ice-volume variations on millennial timescales as indicated by sea-level records. This suggests that either the origin of the latter is not the NH or that processes not represented in our study, notably variations in oceanic conditions, need to be invoked to explain millennial-scale ice-volume fluctuations. We finally provide here both our derived climate evolution of the LGP using the three methods as well as the resulting ice-sheet configurations. These could be of interest for future studies dealing with the atmospheric or/and oceanic consequences of transient ice-sheet evolution throughout the LGP and as a source of climate input to other ice-sheet models.

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Topographic and Glaciological Controls on Holocene Ice-Sheet Margin Dynamics. Central West Greenland

Annals of Glaciology ◽

10.3189/s0260305500008806 ◽

1990 ◽

Vol 14 ◽

pp. 307-310 ◽

Cited By ~ 11

Author(s):

C.R. Warren ◽

N.R.J. Hulton

Keyword(s):

Ice Sheet ◽

Greenland Ice Sheet ◽

Glacial Maximum ◽

Warm Climate ◽

Short Term ◽

The West ◽

West Greenland ◽

The Past

The retreat of the West Greenland ice sheet from its Sisimiut (Wisconsinan) glacial maximum, was punctuated by a series of Stillstands or small readvances that formed numerous moraines. These landforms have been interpreted in the past as the result of short-term, regional falls in ablation-season temperatures. However, mapping of the geomorphological evidence south of Ilulissat (Jakobshavn) suggests that retreat behaviour was not primarily governed by climate, and therefore that the former ice margins are not palaeoclimatically significant. During warm climate ice-sheet wastage, the successive quasi-stable positions adopted by the ice margin were largely governed by topography. The retreat of the inherently unstable calving glaciers was arrested only at topographically-determined locations where stability could be achieved.

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Limits in detecting acceleration of ice sheet mass loss due to climate variability

Nature Geoscience ◽

10.1038/ngeo1874 ◽

2013 ◽

Vol 6 (8) ◽

pp. 613-616 ◽

Cited By ~ 99

Author(s):

B. Wouters ◽

J. L. Bamber ◽

M. R. van den Broeke ◽

J. T. M. Lenaerts ◽

I. Sasgen

Keyword(s):

Climate Variability ◽

Mass Loss ◽

Ice Sheet

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Firn temperature and meltwater refreezing in the lower accumulation area of the Greenland ice sheet, Pâkitsoq, West Greenland

Rapport Grønlands Geologiske Undersøgelse ◽

10.34194/rapggu.v159.8218 ◽

1993 ◽

Vol 159 ◽

pp. 109-114

Author(s):

R.J Braithwaite

Keyword(s):

Sea Level ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

International Project ◽

Sea Level Changes ◽

West Greenland ◽

Degree Day ◽

Air Temperatures ◽

Surface Melt ◽

High Degree

Firn temperatures and meltwater refreezing are studied in the lower accumulation area of the Greenland ice sheet as part of an international project on sea level changes. In the study area, 1440–1620 m a.s.l., meltwater penetrates several metres into the firn and refreezes, warming the firn by 5–7°C compared with annual air temperatures. This firn warming is closely related to surface melt which can be estimated by several methods. A relatively high degree-day factor is needed to account for the melt rates found.

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Reconstructing climate variability from Greenland ice sheet accumulation: An ERA40 study

Geophysical Research Letters ◽

10.1029/2005gl024745 ◽

2005 ◽

Vol 32 (23) ◽

Cited By ~ 21

Author(s):

M. A. Hutterli ◽

C. C. Raible ◽

T. F. Stocker

Keyword(s):

Climate Variability ◽

Ice Sheet ◽

Greenland Ice Sheet

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Assessing ice margin fluctuations on differing timescales: Chronological constraints from Sermeq Kujatdleq and Nordenskiöld Gletscher, central West Greenland

The Holocene ◽

10.1177/0959683618761541 ◽

2018 ◽

Vol 28 (7) ◽

pp. 1160-1172 ◽

Cited By ~ 2

Author(s):

Samuel E Kelley ◽

Jason P Briner ◽

Sandy L O’Hara

Keyword(s):

Late Holocene ◽

Sediment Cores ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Dynamics ◽

West Greenland ◽

Southern Site ◽

Ice Velocity ◽

Observational Record ◽

Local Variability

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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Freshwater input into a low-Arctic Fjord in West Greenland: Timing, drivers and model evaluation

10.5194/egusphere-egu21-14149 ◽

2021 ◽

Author(s):

Jakob Abermann ◽

Kirsty Langley ◽

Sille Myreng ◽

Dorthe Petersen ◽

Kerstin Rasmussen ◽

...

Keyword(s):

Large Scale ◽

Temporal Trends ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Base Flow ◽

Minor Role ◽

Freshwater Flux ◽

Freshwater Input ◽

West Greenland ◽

Specific Discharge

The majority of the freshwater input from Greenland stems from the Greenland Ice Sheet. Despite its importance in terms of freshwater totals, there is a much higher number of individual catchments disconnected from the ice sheet contributing on average about 26% of the total Greenland freshwater flux. Most of those catchments have local glacier cover, only very few of them are instrumented and little scientific literature exists. We present a dataset of 12 years of discharge of four catchments less than 15 km apart, that are different in size (between 7 and 32 km&#178;), local glacier coverage (4-11%) and lake cover (0-5%). They all drain into Kobbefjord, a well-studied fjord in West Greenland, near Greenland&#8217;s capital Nuuk. We find that annual specific discharge totals vary greatly (between 1.2 and 1.9 m/yr on a 12-year average within 15 km) due to a general climatic gradient and different strengths of orographic shading. The seasonal cycle differs among the sites mainly due to different exposure to solar radiation as a driver for major snowmelt; small ice coverage in the catchments plays only a minor role in discharge variability. Dry years generally increase the magnitude of spatial gradients in specific discharge and no significant temporal trends have been found in the studied catchments. On the sub-daily scale, the presence and elevation of lakes determines the catchment&#8217;s response during sunny days, leading to a difference in the timing of maximum discharge of between 7 and 12 hours depending on the site and the time of the year. The response of discharge to major precipitation events is discussed, where uniform reaction is found for the catchments with no lakes near the gauge and a delay of between 5 and 7 hours in the catchment with low-lying lakes. A comparison with a recently published modelled discharge time series on individual catchment scale shows the model&#8217;s capability of reproducing both snowmelt and large-scale storm events; however, the strong spatial heterogeneity of discharge magnitude and timing as well as the presence and variability of base-flow is not captured. We discuss methods to combine observational data with existing model output in order to improve the potential of their combined usage on the Greenland-scale.

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