scholarly journals Advection and non-climate impacts on the South Pole Ice Core

2020 ◽  
Vol 16 (3) ◽  
pp. 819-832 ◽  
Author(s):  
Tyler J. Fudge ◽  
David A. Lilien ◽  
Michelle Koutnik ◽  
Howard Conway ◽  
C. Max Stevens ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Sheet ◽  
Climate Impacts ◽  
Lapse Rate ◽  
South Pole ◽  
Elevation Change ◽  
The South ◽  
The Core ◽  
Core Site ◽  
The Impact

Abstract. The South Pole Ice Core (SPICEcore), which spans the past 54 300 years, was drilled far from an ice divide such that ice recovered at depth originated upstream of the core site. If the climate is different upstream, the climate history recovered from the core will be a combination of the upstream conditions advected to the core site and temporal changes. Here, we evaluate the impact of ice advection on two fundamental records from SPICEcore: accumulation rate and water isotopes. We determined past locations of ice deposition based on GPS measurements of the modern velocity field spanning 100 km upstream, where ice of ∼20 ka age would likely have originated. Beyond 100 km, there are no velocity measurements, but ice likely originates from Titan Dome, an additional 90 km distant. Shallow radar measurements extending 100 km upstream from the core site reveal large (∼20 %) variations in accumulation but no significant trend. Water isotope ratios, measured at 12.5 km intervals for the first 100 km of the flowline, show a decrease with elevation of −0.008 ‰ m−1 for δ18O. Advection adds approximately 1 ‰ for δ18O to the Last Glacial Maximum (LGM)-to-modern change. We also use an existing ensemble of continental ice-sheet model runs to assess the ice-sheet elevation change through time. The magnitude of elevation change is likely small and the sign uncertain. Assuming a lapse rate of 10 ∘C km−1 of elevation, the inference of LGM-to-modern temperature change is ∼1.4 ∘C smaller than if the flow from upstream is not considered.

scholarly journals Advection (non-climate) impact on the South Pole Ice Core

2019 ◽  
Author(s):  
Tyler J. Fudge ◽  
David A. Lilien ◽  
Michelle Koutnik ◽  
Howard Conway ◽  
C. Max Stevens ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Ice Core ◽  
Lapse Rate ◽  
South Pole ◽  
The South ◽  
Climate History ◽  
The Core ◽  
The Past ◽  
Core Site ◽  
The Impact

Abstract. The South Pole Ice Core (SPICEcore), which spans the past 54,300 years, was drilled far from an ice divide such that ice recovered at depth originated at a location upstream of the current core site. If the climate is different upstream, the climate history recovered from the core will be a combination of the upstream conditions advected to the core site and the temporal changes we seek to recover. Here, we evaluate the impact of ice advection on two fundamental records from SPICEcore: accumulation rate and water isotopes. We determined the past locations of ice deposition based on GPS measurements of the modern velocity field spanning 100 km upstream where ice of ~ 20 ka age would likely have originated. Beyond 100 km, there are no velocity measurements, but ice likely originates from Titan Dome, an additional 90 km distant. Shallow radar measurements extending 100 km upstream from the core site reveal large (~ 20 %) variations in accumulation but no significant trend. Water isotope ratios, measured at 12.5 km intervals for the first 100 km of the flowline, show a decrease with elevation (and distance upstream) of -0.008 ‰ m−1 for δ18O. Advection therefore adds approximately 1 ‰ for δ18O to the LGM-to-modern change. Assuming a lapse rate of 10 °C per km of elevation, the LGM-to-modern temperature change is ~ 1.5 °C greater than if the ice had been deposited at a fixed location.

scholarly journals Sea-ice feedbacks influence the isotopic signature of Greenland Ice Sheet elevation changes: Last Interglacial HadCM3 simulations

2020 ◽  
Author(s):  
Irene Malmierca-Vallet ◽  
Louise C. Sime ◽  
Paul J. Valdes ◽  
Julia C. Tindall
Keyword(s):  
Sea Ice ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Lapse Rate ◽  
Last Interglacial ◽  
Elevation Change ◽  
Elevation Gradients ◽  
Lapse Rates

Abstract. Changes in the Greenland ice sheet (GIS) affect global sea level. Greenland stable water isotope (δ18O) records from ice cores offer information on past changes in the surface of the GIS. Here, we use the isotope-enabled HadCM3 climate model to simulate a set of Last Interglacial (LIG) idealised GIS surface elevation change scenarios focusing on GIS ice core sites. We investigate how δ18O depends on the magnitude and sign of GIS elevation change and evaluate how the response is altered by sea ice changes. We find that modifying GIS elevation induces changes in Northern Hemisphere atmospheric circulation, sea ice and precipitation patterns. These climate feedbacks lead to ice core-averaged isotopic lapse rates of 0.49 ‰ per 100 m for the lowered GIS states and 0.29 ‰ per 100 m for the enlarged GIS states. This is lower than the spatially derived Greenland lapse rates of 0.62–0.72 ‰ per 100 m. These results thus suggest non-linearities in the isotope-elevation relationship, and have consequences for the interpretation of past elevation and climate changes across Greenland. In particular, our results suggest that winter sea ice changes may significantly influence isotopic-elevation gradients: winter sea ice effect can decrease (increase) modelled core-averaged isotopic lapse rate values by about -19 % (and +28 %) for the lowered (enlarged) GIS states respectively. The largest influence of sea ice on δ18O changes is found in coastal regions like the Camp Century site.

scholarly journals Sea ice feedbacks influence the isotopic signature of Greenland ice sheet elevation changes: last interglacial HadCM3 simulations

2020 ◽  
Vol 16 (6) ◽  
pp. 2485-2508
Author(s):  
Irene Malmierca-Vallet ◽  
Louise C. Sime ◽  
Paul J. Valdes ◽  
Julia C. Tindall
Keyword(s):  
Sea Ice ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Lapse Rate ◽  
Last Interglacial ◽  
Elevation Change ◽  
Elevation Gradients ◽  
Lapse Rates

Abstract. Changes in the Greenland ice sheet (GIS) affect global sea level. Greenland stable water isotope (δ18O) records from ice cores offer information on past changes in the surface of the GIS. Here, we use the isotope-enabled Hadley Centre Coupled Model version 3 (HadCM3) climate model to simulate a set of last interglacial (LIG) idealised GIS surface elevation change scenarios focusing on GIS ice core sites. We investigate how δ18O depends on the magnitude and sign of GIS elevation change and evaluate how the response is altered by sea ice changes. We find that modifying GIS elevation induces changes in Northern Hemisphere atmospheric circulation, sea ice and precipitation patterns. These climate feedbacks lead to ice-core-averaged isotopic lapse rates of 0.49 ‰ (100 m)−1 for the lowered GIS states and 0.29 ‰ (100 m)−1 for the enlarged GIS states. This is lower than the spatially derived Greenland lapse rates of 0.62–0.72 ‰ (100 m)−1. These results thus suggest non-linearities in the isotope–elevation relationship and have consequences for the interpretation of past elevation and climate changes across Greenland. In particular, our results suggest that winter sea ice changes may significantly influence isotope–elevation gradients: winter sea ice effect can decrease (increase) modelled core-averaged isotopic lapse rate values by about −19 % (and +28 %) for the lowered (enlarged) GIS states, respectively. The largest influence of sea ice on δ18O changes is found in coastal regions like the Camp Century site.

scholarly journals The Debris-Laden Ice at the Bottom of the Greenland Ice Sheet

1979 ◽  
Vol 23 (89) ◽  
pp. 193-207 ◽  
Author(s):  
Susan Herron ◽  
Hoar ◽  
Chester C. Langway
Keyword(s):  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
High Deformation ◽  
Fine Grained ◽  
Free Zone ◽  
The Core ◽  
Oxidation Of Methane ◽  
Particle Aggregates ◽  
Glacier Ice

AbstractThe Camp Century, Greenland, ice core was recovered from a bore hole which extended 1 375 m from the surface of the Greenland ice sheet to the ice/sub-ice interface. The bottom 15.7 m of the core contain over 300 alternating bands of clear and debris-laden ice. The size of the included debris ranges from particles less than 2 μm in diameter to particle aggregates which are a maximum of 3 cm in diameter: the average debris concentration is 0.24ºº by weight. The debris size, concentration, and composition indicate that the debris originates from the till-like material directly below the debris-laden ice. The total gas concentration averages 51 ml/kg ice compared to the average of 101 ml/kg ice for the top 1 340 m. The gas composition of debris-bearing ice has apparently been modified by the oxidation of methane as reflected by traces of methane, high CO2 levels, and low O2 levels with respect to atmospheric air. Argon, which is not affected by the oxidation, shows an enrichment in samples with lower gas concentrations. Both the low gas concentrations in the debris-laden zone and the argon enrichment may be explained by the downward diffusion of gases from bubbly glacier ice into an originally bubble-free zone of refrozen debris-laden ice. Ice texture and ice-fabric analyses reveal extremely fine-grained ice and highly preferred crystal orientation in the lowermost 10 m of the core, indicating a zone of high deformation.

Tephra in the Greenland Ice cores: Insights into Icelandic volcano-climate impacts

2021 ◽  
Author(s):  
Imogen Gabriel ◽  
Gill Plunkett ◽  
Peter Abbott ◽  
Bergrún Óladóttir ◽  
Joseph McConnell ◽  
...  
Keyword(s):  
High Resolution ◽  
Ice Core ◽  
Ice Cores ◽  
Volcanic Eruptions ◽  
Climate Impacts ◽  
Geochemical Analysis ◽  
Volcanic Events ◽  
Societal Impacts ◽  
The Impact ◽  
Ice Core Records

<p>Volcanic eruptions are considered as one of the primary natural drivers for changes in the global climate system and understanding the impact of past eruptions on the climate is integral to adopt appropriate responses towards future volcanic eruptions.</p><p>The Greenland ice core records are dominated by Icelandic eruptions, with several volcanic systems (Katla, Hekla, Bárðarbunga-Veiðivötn and Grimsvötn) being highly active throughout the Holocene. A notable period of increased Icelandic volcanic activity occurred between 500-1250 AD and coincided with climatic changes in the North Atlantic region which may have facilitated the Viking settlement of Greenland and Iceland. However, a number of these volcanic events are poorly constrained (duration and magnitude). Consequently, the Greenland ice cores offer the opportunity to reliably reconstruct past Icelandic volcanism (duration, magnitude and frequency) due to their high-resolution, the proximity of Iceland to Greenland and subsequent increased likelihood of volcanic fallout deposits (tephra particles and sulphur aerosols) being preserved. However, both the high frequency of eruptions between 500-1250 AD and the geochemical similarity of Iceland’s volcanic centres present challenges in making the required robust geochemical correlations between the source volcano and the ice core records and ultimately reliably assessing the climatic-societal impacts of these eruptions.</p><p>To address this, we use two Greenland ice core records (TUNU2013 and B19) and undertake geochemical analysis on tephra from the volcanic events in the selected time window which have been detected and sampled using novel techniques (insoluble particle peaks and sulphur acidity peaks). Further geochemical analysis of proximal material enables robust correlations to be made between the events in the ice core records and their volcanic centres. The high-resolution of these polar archives provides a precise age for the event and when utilised alongside other proxies (i.e. sulphur aerosols), both the duration and magnitude of these eruptions can be constrained, and the climatic-societal impacts of these eruptions reliably assessed.</p>

scholarly journals Modeling ice birefringence and oblique radio wave propagation for neutrino detection at the South Pole

2020 ◽  
Vol 61 (81) ◽  
pp. 84-91 ◽  
Author(s):  
T. M. Jordan ◽  
D. Z. Besson ◽  
I. Kravchenko ◽  
U. Latif ◽  
B. Madison ◽  
...  
Keyword(s):  
Time Delays ◽  
Ice Core ◽  
High Energy ◽  
Propagation Model ◽  
Neutrino Interaction ◽  
Crystallographic Axis ◽  
South Pole ◽  
The South ◽  
Range Estimation ◽  
Ice Flow

AbstractThe Askaryan Radio Array (ARA) experiment at the South Pole is designed to detect high-energy neutrinos which, via in-ice interactions, produce coherent radiation at frequencies up to 1000 MHz. Characterization of ice birefringence, and its effect upon wave polarization, is proposed to enable range estimation to a neutrino interaction and hence aid in neutrino energy reconstruction. Using radio transmitter calibration sources, the ARA collaboration recently measured polarization-dependent time delay variations and reported significant time delays for trajectories perpendicular to ice flow, but not parallel. To explain these observations, and assess the capability for range estimation, we use fabric data from the SPICE ice core to model ice birefringence and construct a bounding radio propagation model that predicts polarization time delays. We compare the model with new data from December 2018 and demonstrate that the measurements are consistent with the prevailing horizontal crystallographic axis aligned near-perpendicular to ice flow. The study supports the notion that range estimation can be performed for near flow-perpendicular trajectories, although tighter constraints on fabric orientation are desirable for improving the accuracy of estimates.

scholarly journals δD And δ18O In South Pole Snow: Further Comparison With Meteorological Data and The Record From the Last Millennium (Abstract)

1988 ◽  
Vol 11 ◽  
pp. 208
Author(s):  
J. R. Petit ◽  
J. Jouzel ◽  
J. C. White ◽  
Qian Qiu-yu ◽  
M. Legrand ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Water Cycle ◽  
Meteorological Data ◽  
Ice Core ◽  
Snow Accumulation ◽  
South Pole ◽  
The South ◽  
Isotope Record ◽  
Δd And Δ18o ◽  
Isotope Content

The stable-isotope content of precipitation (δD and δ18O) is governed by the successive fractionation processes which occur during the atmospheric water cycle. As a result there is, in polar areas, a well-obeyed and theoretically well-understood linear relationship between the mean istopic content of snow and its mean temperature of formation. This relationship is well documented on a spatial scale but poorly known for a given site on a temporal basis, the main reason being that relatively long-term and sufficiently detailed meteorological data are only available for a few polar sites. The South Pole appears to be a suitable place for such a study because: (i) snow accumulation is high enough (∼20 cm of snow per year), thus reducing the possibility that annual layers will be lost as a result of wind; (ii) seasonal variation in isotope content is still preserved in snow up to 50 years old; (iii) meteorological data are available from the time the station was opened in 1957. Our previous studies of surface and recently deposited snow at the South Pole were very encouraging in this respect; they have been extended with a two-fold purpose: (i) to test the geographical representativity of the isotope record by comparing results from various cores taken within a 10 km radius of the station. The cores are dated by various techniques, such as stratigraphy, seasonal variation in isotopic content, beta-radioactivity fall-out layers, and detection by solid conductivity measurements of the high “spike” which is thought to correspond to the 1815 Tambora eruption; (ii) to discuss the South Pole isotope record over the last 1000 years as recovered from a 127 m deep ice core.

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