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  • 11
    Online Resource
    Online Resource
    The Impact of Regional Arctic Sea Ice Loss on Atmospheric Circulation and the NAO
    American Meteorological Society ; 2016
    In:  Journal of Climate Vol. 29, No. 2 ( 2016-01-15), p. 889-902
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 29, No. 2 ( 2016-01-15), p. 889-902
    Abstract: Reduction of the Arctic sea ice cover can affect the atmospheric circulation and thus impact the climate beyond the Arctic. The atmospheric response may, however, vary with the geographical location of sea ice loss. The atmospheric sensitivity to the location of sea ice loss is studied using a general circulation model in a configuration that allows combination of a prescribed sea ice cover and an active mixed layer ocean. This hybrid setup makes it possible to simulate the isolated impact of sea ice loss and provides a more complete response compared to experiments with fixed sea surface temperatures. Three investigated sea ice scenarios with ice loss in different regions all exhibit substantial near-surface warming, which peaks over the area of ice loss. The maximum warming is found during winter, delayed compared to the maximum sea ice reduction. The wintertime response of the midlatitude atmospheric circulation shows a nonuniform sensitivity to the location of sea ice reduction. While all three scenarios exhibit decreased zonal winds related to high-latitude geopotential height increases, the magnitudes and locations of the anomalies vary between the simulations. Investigation of the North Atlantic Oscillation reveals a high sensitivity to the location of the ice loss. The northern center of action exhibits clear shifts in response to the different sea ice reductions. Sea ice loss in the Atlantic and Pacific sectors of the Arctic cause westward and eastward shifts, respectively.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-15-0315.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2016
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  • 12
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    Author Correction: Volcanic influence on centennial to millennial Holocene Greenland temperature change
    Springer Science and Business Media LLC ; 2018
    In:  Scientific Reports Vol. 8, No. 1 ( 2018-03-06)
    Details
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 8, No. 1 ( 2018-03-06)
    Abstract: A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.
    Type of Medium: Online Resource
    ISSN: 2045-2322
    URL: Article
    DOI: 10.1038/s41598-018-21307-y
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2018
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  • 13
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    Simulating the Last Interglacial Greenland stable water isotope peak: The role of Arctic sea ice changes
    Elsevier BV ; 2018
    In:  Quaternary Science Reviews Vol. 198 ( 2018-10), p. 1-14
    Details
    In: Quaternary Science Reviews, Elsevier BV, Vol. 198 ( 2018-10), p. 1-14
    Type of Medium: Online Resource
    ISSN: 0277-3791
    URL: Article
    DOI: 10.1016/j.quascirev.2018.07.027
    RVK:
    RA 1000
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2018
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  • 14
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    Greenland and Canadian Arctic ice temperature profiles database
    Copernicus GmbH ; 2023
    In:  The Cryosphere Vol. 17, No. 9 ( 2023-09-08), p. 3829-3845
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 17, No. 9 ( 2023-09-08), p. 3829-3845
    Abstract: Abstract. Here, we present a compilation of 95 ice temperature profiles from 85 boreholes from the Greenland ice sheet and peripheral ice caps, as well as local ice caps in the Canadian Arctic. Profiles from only 31 boreholes (36 %) were previously available in open-access data repositories. The remaining 54 borehole profiles (64 %) are being made digitally available here for the first time. These newly available profiles, which are associated with pre-2010 boreholes, have been submitted by community members or digitized from published graphics and/or data tables. All 95 profiles are now made available in both absolute (meters) and normalized (0 to 1 ice thickness) depth scales and are accompanied by extensive metadata. These metadata include a transparent description of data provenance. The ice temperature profiles span 70 years, with the earliest profile being from 1950 at Camp VI, West Greenland. To highlight the value of this database in evaluating ice flow simulations, we compare the ice temperature profiles from the Greenland ice sheet with an ice flow simulation by the Parallel Ice Sheet Model (PISM). We find a cold bias in modeled near-surface ice temperatures within the ablation area, a warm bias in modeled basal ice temperatures at inland cold-bedded sites, and an apparent underestimation of deformational heating in high-strain settings. These biases provide process level insight on simulated ice temperatures.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    URL: Article
    DOI: 10.5194/tc-17-3829-2023
    DOI: 10.5194/tc-17-3829-2023-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2023
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  • 15
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    High-frequency climate variability in the Holocene from a coastal-dome ice core in east-central Greenland
    Copernicus GmbH ; 2020
    In:  Climate of the Past Vol. 16, No. 4 ( 2020-07-31), p. 1369-1386
    Details
    In: Climate of the Past, Copernicus GmbH, Vol. 16, No. 4 ( 2020-07-31), p. 1369-1386
    Abstract: Abstract. An ice core drilled on the Renland ice cap in east-central Greenland contains a continuous climate record dating through the last glacial period. The Renland record is valuable because the coastal environment is more likely to reflect regional sea surface conditions compared to inland Greenland ice cores that capture synoptic variability. Here we present the δ18O water isotope record for the Holocene, in which decadal-scale climate information is retained for the last 8 kyr, while the annual water isotope signal is preserved throughout the last 2.6 kyr. To investigate regional climate information preserved in the water isotope record, we apply spectral analysis techniques to a 300-year moving window to determine the mean strength of varying frequency bands through time. We find that the strength of 15–20-year δ18O variability exhibits a millennial-scale signal in line with the well-known Bond events. Comparison to other North Atlantic proxy records suggests that the 15–20-year variability may reflect fluctuating sea surface conditions throughout the Holocene, driven by changes in the strength of the Atlantic Meridional Overturning Circulation. Additional analysis of the seasonal signal over the last 2.6 kyr reveals that the winter δ18O signal has experienced a decreasing trend, while the summer signal has predominantly remained stable. The winter trend may correspond to an increase in Arctic sea ice cover, which is driven by a decrease in total annual insolation, and is also likely influenced by regional climate variables such as atmospheric and oceanic circulation. In the context of anthropogenic climate change, the winter trend may have important implications for feedback processes as sea ice retreats in the Arctic.
    Type of Medium: Online Resource
    ISSN: 1814-9332
    URL: Article
    DOI: 10.5194/cp-16-1369-2020
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2217985-9
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  • 16
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    Holocene tephras highlight complexity of volcanic signals in Greenland ice cores : HOLOCENE TEPHRAS IN GREENLAND ICE CORES
    American Geophysical Union (AGU) ; 2012
    In:  Journal of Geophysical Research: Atmospheres Vol. 117, No. D21 ( 2012-11-16), p. n/a-n/a
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 117, No. D21 ( 2012-11-16), p. n/a-n/a
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2012JD017698
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2012
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    detail.hit.zdb_id: 2016800-7
    detail.hit.zdb_id: 161666-3
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 2969341-X
    detail.hit.zdb_id: 161665-1
    detail.hit.zdb_id: 3094268-8
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 3094181-7
    detail.hit.zdb_id: 3094219-6
    detail.hit.zdb_id: 3094167-2
    detail.hit.zdb_id: 2220777-6
    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
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  • 17
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    The duration of the Bølling-Allerød period (Greenland Interstadial 1) in the GRIP ice core
    International Glaciological Society ; 2005
    In:  Annals of Glaciology Vol. 42 ( 2005), p. 337-344
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 42 ( 2005), p. 337-344
    Abstract: A new dating of the Bølling-Allerød period (Greenland Interstadial event 1) in the GRIP ice core is presented. Newly measured profiles of δD and δ 18 O, as well as existing profiles of Ca 2+ , NH 4 + , dust and NO3 – , have been used for the dating. As seasonal variations can be observed in all six components, it was possible to simultaneously count annual layers in the profiles in order to obtain a multi-parameter dating. The new data presented in this study include a total of 36.85 m of stable-isotope profiles of 1 cm resolution from five sections of the Bølling-Allerød period in the GRIP ice core. The annual-layer counting suggests a duration of the complete Bølling-Allerød period, as revealed in the GRIP ice core, of 1627 ± 52 years. This estimate contrasts with an earlier finding from the same GRIP ice core, where the Bølling-Allerød was found to span 2168 years (Hammer, in press). This estimate was based on layer counting, using dust concentrations only.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/172756405781812556
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2005
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  • 18
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    Ice thickness and volume of the Renland Ice Cap, East Greenland
    Cambridge University Press (CUP) ; 2021
    In:  Journal of Glaciology Vol. 67, No. 264 ( 2021-08), p. 714-726
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP), Vol. 67, No. 264 ( 2021-08), p. 714-726
    Abstract: To assess the amount of ice volume stored in glaciers or ice caps, a method to estimate ice thickness distribution is required for glaciers where no direct observations are available. In this study, we use an existing inverse method to estimate the bedrock topography and ice thickness of the Renland Ice Cap, East Greenland, using satellite-based observations of the surface topography. The inverse approach involves a procedure in which an ice dynamical model is used to build-up an ice cap in steady state with climate forcing from a regional climate model, and the bedrock is iteratively adjusted until the modelled and observed surface topography match. We validate our model results against information from airborne radar data and satellite observed surface velocity, and we find that the inferred ice thickness and thereby the stored total volume of the ice cap is sensitive to the assumed ice softness and basal slipperiness. The best basal model parameters for the Renland Ice Cap are determined and the best estimated total ice volume of 384 km 3 is found. The Renland Ice Cap is particularly interesting because of its location at a high elevation plateau and hence assumed low sensitivity to climate change.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/jog.2021.11
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2021
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    SSG: 14
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  • 19
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    Bipolar volcanic synchronization of abrupt climate change in Greenland and Antarctic ice cores during the last glacial period
    Copernicus GmbH ; 2020
    In:  Climate of the Past Vol. 16, No. 4 ( 2020-08-19), p. 1565-1580
    Details
    In: Climate of the Past, Copernicus GmbH, Vol. 16, No. 4 ( 2020-08-19), p. 1565-1580
    Abstract: Abstract. The last glacial period is characterized by a number of millennial climate events that have been identified in both Greenland and Antarctic ice cores and that are abrupt in Greenland climate records. The mechanisms governing this climate variability remain a puzzle that requires a precise synchronization of ice cores from the two hemispheres to be resolved. Previously, Greenland and Antarctic ice cores have been synchronized primarily via their common records of gas concentrations or isotopes from the trapped air and via cosmogenic isotopes measured on the ice. In this work, we apply ice core volcanic proxies and annual layer counting to identify large volcanic eruptions that have left a signature in both Greenland and Antarctica. Generally, no tephra is associated with those eruptions in the ice cores, so the source of the eruptions cannot be identified. Instead, we identify and match sequences of volcanic eruptions with bipolar distribution of sulfate, i.e. unique patterns of volcanic events separated by the same number of years at the two poles. Using this approach, we pinpoint 82 large bipolar volcanic eruptions throughout the second half of the last glacial period (12–60 ka). This improved ice core synchronization is applied to determine the bipolar phasing of abrupt climate change events at decadal-scale precision. In response to Greenland abrupt climatic transitions, we find a response in the Antarctic water isotope signals (δ18O and deuterium excess) that is both more immediate and more abrupt than that found with previous gas-based interpolar synchronizations, providing additional support for our volcanic framework. On average, the Antarctic bipolar seesaw climate response lags the midpoint of Greenland abrupt δ18O transitions by 122±24 years. The time difference between Antarctic signals in deuterium excess and δ18O, which likewise informs the time needed to propagate the signal as described by the theory of the bipolar seesaw but is less sensitive to synchronization errors, suggests an Antarctic δ18O lag behind Greenland of 152±37 years. These estimates are shorter than the 200 years suggested by earlier gas-based synchronizations. As before, we find variations in the timing and duration between the response at different sites and for different events suggesting an interaction of oceanic and atmospheric teleconnection patterns as well as internal climate variability.
    Type of Medium: Online Resource
    ISSN: 1814-9332
    URL: Article
    URL: Article
    DOI: 10.5194/cp-16-1565-2020
    DOI: 10.5194/cp-16-1565-2020-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
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  • 20
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    Seasonal reconstructions coupling ice core data and an isotope-enabled climate model – methodological implications of seasonality, climate modes and selection of proxy data
    Copernicus GmbH ; 2020
    In:  Climate of the Past Vol. 16, No. 5 ( 2020-09-11), p. 1737-1758
    Details
    In: Climate of the Past, Copernicus GmbH, Vol. 16, No. 5 ( 2020-09-11), p. 1737-1758
    Abstract: Abstract. The research area of climate field reconstructions has developed strongly during the past 20 years, motivated by the need to understand the complex dynamics of the earth system in a changing climate. Climate field reconstructions aim to build a consistent gridded climate reconstruction of different variables, often from a range of climate proxies, using either statistical tools or a climate model to fill the gaps between the locations of the proxy data. Commonly, large-scale climate field reconstructions covering more than 500 years are of annual resolution. In this method study, we investigate the potential of seasonally resolved climate field reconstructions based on oxygen isotope records from Greenland ice cores and an isotope-enabled climate model. Our analogue-type method matches modeled isotope patterns in Greenland precipitation to the patterns of ice core data from up to 14 ice core sites. In a second step, the climate variables of the best-matching model years are extracted, with the mean of the best-matching years comprising the reconstruction. We test a range of climate reconstructions, varying the definition of the seasons and the number of ice cores used. Our findings show that the optimal definition of the seasons depends on the variability in the target season. For winter, the vigorous variability is best captured when defining the season as December–February due to the dominance of large-scale patterns. For summer, which has weaker variability, albeit more persistent in time, the variability is better captured using a longer season of May–October. Motivated by the scarcity of seasonal data, we also test the use of annual data where the year is divided during summer, that is, not following the calendar year. This means that the winter variability is not split and that the annual data then can be used to reconstruct the winter variability. In particularly when reconstructing the sea level pressure and the corresponding main modes of variability, it is important to take seasonality into account, because of changes in the spatial patterns of the modes throughout the year. Targeting the annual mean sea level pressure for the reconstruction lowers the skill simply due to the seasonal geographical shift of the circulation modes. Our reconstructions based on ice core data also show skill for the North Atlantic sea surface temperatures, in particularly during winter for latitudes higher than 50∘ N. In addition, the main modes of the sea surface temperature variability are qualitatively captured by the reconstructions. When testing the skill of the reconstructions using 19 ice cores compared to the ones using eight ice cores, we do not find a clear advantage of using a larger data set. This could be due to a more even spatial distribution of the eight ice cores. However, including European tree-ring data to further constrain the summer temperature reconstruction clearly improves the skill for this season, which otherwise is more difficult to capture than the winter season.
    Type of Medium: Online Resource
    ISSN: 1814-9332
    URL: Article
    URL: Article
    DOI: 10.5194/cp-16-1737-2020
    DOI: 10.5194/cp-16-1737-2020-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2217985-9
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