scholarly journals Firn changes at Colle Gnifetti revealed with a high-resolution process-based physical model approach

2021 ◽  
Vol 15 (7) ◽  
pp. 3181-3205
Author(s):  
Enrico Mattea ◽  
Horst Machguth ◽  
Marlene Kronenberg ◽  
Ward van Pelt ◽  
Manuela Bassi ◽  
...  
Keyword(s):  
High Resolution ◽  
Distributed Simulation ◽  
Meteorological Data ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Balance Model ◽  
Monte Rosa ◽  
Fully Coupled

Abstract. Our changing climate is expected to affect ice core records as cold firn progressively transitions to a temperate state. Thus, there is a need to improve our understanding and to further develop quantitative process modeling, to better predict cold firn evolution under a range of climate scenarios. Here we present the application of a distributed, fully coupled energy balance model, to simulate cold firn at the high-alpine glaciated saddle of Colle Gnifetti (Swiss–Italian Alps) over the period 2003–2018. We force the model with high-resolution, long-term, and extensively quality-checked meteorological data measured in the closest vicinity of the firn site, at the highest automatic weather station in Europe (Capanna Margherita, 4560 m a.s.l.). The model incorporates the spatial variability of snow accumulation rates and is calibrated using several partly unpublished high-altitude measurements from the Monte Rosa area. The simulation reveals a very good overall agreement in the comparison with a large archive of firn temperature profiles. Our results show that surface melt over the glaciated saddle is increasing by 3–4 mm w.e. yr−2 depending on the location (29 %–36 % in 16 years), although with large inter-annual variability. Analysis of modeled melt indicates the frequent occurrence of small melt events (<4 mm w.e.), which collectively represent a significant fraction of the melt totals. Modeled firn warming rates at 20 m depth are relatively uniform above 4450 m a.s.l. (0.4–0.5 ∘C per decade). They become highly variable at lower elevations, with a marked dependence on surface aspect and absolute values up to 2.5 times the local rate of atmospheric warming. Our distributed simulation contributes to the understanding of the thermal regime and evolution of a prominent site for alpine ice cores and may support the planning of future core drilling efforts. Moreover, thanks to an extensive archive of measurements available for comparison, we also highlight the possibilities of model improvement most relevant to the investigation of future scenarios, such as the fixed-depth parametrized routine of deep preferential percolation.

scholarly journals Firn changes at Colle Gnifetti revealed with a high-resolution process-based physical model approach

2021 ◽  
Author(s):  
Enrico Mattea ◽  
Horst Machguth ◽  
Marlene Kronenberg ◽  
Ward van Pelt ◽  
Manuela Bassi ◽  
...  
Keyword(s):  
High Resolution ◽  
Meteorological Data ◽  
Ice Core ◽  
Snow Accumulation ◽  
Balance Model ◽  
Monte Rosa ◽  
First Time ◽  
Fully Coupled ◽  
Marked Tendency

Abstract. Our changing climate is expected to affect ice core records as cold firn progressively transitions to a temperate state. Thus there is a need to improve understanding and further develop quantitative process modeling, to better predict cold firn evolution under a range of climate scenarios. Here we present the application of a distributed, fully coupled energy balance model, to simulate high-alpine cold firn at Colle Gnifetti over the period 2003–2018. For the first time, we force such a model with high-resolution, long-term and extensively quality-checked meteorological data measured in closest vicinity of the firn site, at the Capanna Margherita (4560 m a.s.l.). The model incorporates the spatial variability of snow accumulation rates, and is calibrated using several, partly unpublished high-altitude measurements from the Monte Rosa area. The simulation reveals a very good overall agreement in the comparison with a large archive of firn temperature profiles. The rate of firn warming at 20 m depth is estimated at 0.44 °C per decade. Our results show that surface melt over the glaciated saddle is increasing by 3–4 mm w.e. yr−2 depending on the location (29–36 % in 16 years), although with large inter-annual variability. Analysis of modeled melt indicates a marked tendency towards small melt events (

scholarly journals Firn changes at Colle Gnifetti revealed with a high-resolution process-based physical model approach

2021 ◽  
Author(s):  
Enrico Mattea ◽  
Horst Machguth ◽  
Marlene Kronenberg ◽  
Ward van Pelt ◽  
Manuela Bassi ◽  
...  
Keyword(s):  
High Resolution ◽  
Meteorological Data ◽  
Ice Core ◽  
Snow Accumulation ◽  
Physical Models ◽  
Surface Model ◽  
Dry Conditions ◽  
Resolution Analysis ◽  
Warming Rate ◽  
Monte Rosa

&lt;p&gt;Cold firn is progressively transitioning to a temperate state under a changing climate. This process is expected to affect ice core records and the mass balance of cold and polythermal glaciers. Thus there is a need to gain better understanding of this transition and develop quantitative, physical models, to predict cold firn evolution under a range of climate scenarios.&lt;/p&gt;&lt;p&gt;Here we present the application of a distributed, fully coupled energy balance and sub-surface model, to simulate high-alpine cold firn at Colle Gnifetti over the period 2003&amp;#8211;2018. For the first time, we force such a model with high-resolution, long-term, quality-checked meteorological data measured in closest vicinity of the firn site, at the highest weather station in Europe (Capanna Margherita, 4560 m a.s.l.). The model includes the spatial variability of snow accumulation rates, and is calibrated using several, partly unpublished high-altitude measurements from the Monte Rosa area.&lt;/p&gt;&lt;p&gt;Overall, the simulated firn temperature profiles reach a very good agreement in comparison with a large archive of borehole measurements. Our results show a 20 m-depth firn warming rate of 0.44 &amp;#176;C per decade. Moreover, we find that surface melt over the glaciated saddle is increasing by 3&amp;#8211;4 mm w.e. yr&lt;sup&gt;-2&lt;/sup&gt; (+29&amp;#8211;36 % in 16 years) depending on the location, although with a large inter-annual variability. The simulation also indicates that atmospheric humidity is a prominent control over melt occurrence, with considerable amounts of sublimation taking place in dry conditions. Hourly-resolution analysis of the melt dynamics reveals a marked tendency towards frequent, small melt events (&lt; 4 mm w.e.): these collectively represent a significant fraction of the total amounts.&lt;/p&gt;

scholarly journals Climatic and atmospheric circulation pattern variability from ice-core isotope/geochemistry records (Altai, Tien Shan and Tibet)

2006 ◽  
Vol 43 ◽  
pp. 49-60 ◽  
Author(s):  
Vladimir B. Aizen ◽  
Elena M. Aizen ◽  
Daniel R. Joswiak ◽  
Koji Fujita ◽  
Nozomu Takeuchi ◽  
...  
Keyword(s):  
Air Temperature ◽  
Isotope Geochemistry ◽  
Eastern Mediterranean ◽  
Meteorological Data ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Tien Shan ◽  
Synoptic Climatology ◽  
The Tibetan Plateau

AbstractSeveral firn/ice cores were recovered from the Siberian Altai (Belukha plateau), central Tien Shan (Inilchek glacier) and the Tibetan Plateau (Zuoqiupu glacier, Bomi) from 1998 to 2003. The comparison analyses of stable-isotope/geochemistry records obtained from these firn/ice cores identified the physical links controlling the climate-related signals at the seasonal-scale variability. The core data related to physical stratigraphy, meteorology and synoptic atmospheric dynamics were the basis for calibration, validation and clustering of the relationships between the firn-/ice-core isotope/ geochemistry and snow accumulation, air temperature and precipitation origin. The mean annual accumulation (in water equivalent) was 106 gcm−2 a−1 at Inilchek glacier, 69 gcm−2 a−1 at Belukha and 196 g cm−2 a−1 at Zuoqiupu. The slopes in regression lines between the δ18O ice-core records and air temperature were found to be positive for the Tien Shan and Altai glaciers and negative for southeastern Tibet, where heavy amounts of isotopically depleted precipitation occur during summer monsoons. The technique of coupling synoptic climatology and meteorological data with δ18O and d-excess in firn-core records was developed to determine climate-related signals and to identify the origin of moisture. In Altai, two-thirds of accumulation from 1984 to 2001 was formed from oceanic precipitation, and the rest of the precipitation was recycled over Aral–Caspian sources. In the Tien Shan, 87% of snow accumulation forms by precipitation originating from the Aral–Caspian closed basin, the eastern Mediterranean and Black Seas, and 13% from the North Atlantic.

scholarly journals Temperature and precipitation signal in two Alpine ice cores over the period 1961–2001

2012 ◽  
Vol 8 (6) ◽  
pp. 5867-5891 ◽  
Author(s):  
I. Mariani ◽  
A. Eichler ◽  
S. Brönnimann ◽  
R. Auchmann ◽  
T. M. Jenk ◽  
...  
Keyword(s):  
Meteorological Data ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Spatial Correlations ◽  
Annual Basis ◽  
Temperature And Precipitation ◽  
Time Period ◽  
Regional Temperature ◽  
Relationship Of

Abstract. Water stable isotope ratios and net snow accumulation in ice cores are usually interpreted as temperature and precipitation proxies. However, only in a few cases a direct calibration with instrumental data has been attempted. In this study we took advantage of the dense network of observations in the European Alpine region to rigorously test the relationship of the proxy data from two highly-resolved ice cores with local temperature and precipitation, respectively, on an annual basis. We focused on the time period 1961–2001 with the highest amount and quality of meteorological data and the minimal uncertainty in ice core dating (±1 yr). The two ice cores come from Fiescherhorn glacier (Northern Alps, 3900 m a.s.l.) and Grenzgletscher (Southern Alps, 4200 m a.s.l.). Due to the orographic barrier, the two flanks of the Alpine chain are affected by distinct patterns of precipitation. Therefore, the different location of the two ice cores offers the unique opportunity to test whether the precipitation proxy reflects this very local condition. We obtained a significant spatial correlation between annual δ18O and regional temperature at Fiescherhorn. Due to the pronounced intraseasonal to interannual variability of precipitation at Grenzgletscher, significant results were only found when weighting the temperature with precipitation. For this site, disentangling the temperature from the precipitation signal was thus not possible. Significant spatial correlations between net accumulation and precipitation were found for both sites but required the record from the Fiescherhorn glacier to be shifted by −1 yr (within the dating uncertainty). The study underlines that even for well-resolved ice core records, interpretation of proxies on an annual or even sub-annual basis remains critical. This is due to both, dating issues and the fact that the signal preservation intrinsically depends on precipitation.

scholarly journals An 800 year high-resolution black carbon ice-core record from Lomonosovfonna, Svalbard

2018 ◽  
Author(s):  
Dimitri Osmont ◽  
Isabel A. Wendl ◽  
Loïc Schmidely ◽  
Michael Sigl ◽  
Carmen P. Vega ◽  
...  
Keyword(s):  
High Resolution ◽  
Black Carbon ◽  
20Th Century ◽  
Biomass Burning ◽  
Ice Core ◽  
Ice Cores ◽  
The Arctic ◽  
Snow Albedo ◽  
Decadal Scale

Abstract. Produced by the incomplete combustion of fossil fuel and biomass, black carbon (BC) contributes to Arctic warming by reducing snow albedo and thus triggering a snow-albedo feedback leading to increased snow melting. Therefore, it is of high importance to assess past BC emissions to better understand and constrain their role. However, only few long-term BC records are available from the Arctic, mainly originating from Greenland ice cores. Here, we present the first long-term and high-resolution refractory black carbon (rBC) record from Svalbard, derived from the analysis of two ice cores drilled at the Lomonosovfonna ice field in 2009 (LF-09) and 2011 (LF-11) and covering 800 years of atmospheric emissions. Our results show that rBC concentrations strongly increased from 1860 on due to anthropogenic emissions and reached two maxima, at the end of the 19th century and in the middle of the 20th century. No increase in rBC concentrations during the last decades was observed, which is corroborated by atmospheric measurements elsewhere in the Arctic but contradicts a previous study from another ice core from Svalbard. While melting may affect BC concentrations during periods of high temperatures, rBC concentrations remain well-preserved prior to the 20th century due to lower temperatures inducing little melt. Therefore, the preindustrial rBC record (before 1800), along with ammonium (NH4+), formate (HCOO−) and specific organic markers (vanillic acid (VA) and p-hydroxybenzoic acid (p-HBA)), was used as a proxy for biomass burning. Despite numerous single events, no long-term trend was observed over the time period 1222–1800 for rBC and NH4+. In contrast, formate, VA and p-HBA experience multi-decadal peaks reflecting periods of enhanced biomass burning. Most of the background variations and single peak events are corroborated by other ice-core records from Greenland and Siberia. We suggest that the paleofire record from the LF ice core primarily reflects biomass burning episodes from Northern Eurasia, induced by decadal-scale climatic variations.

Atmospheric history of carbon monoxide since preindustrial times reconstructed from multiple Greenland ice cores

2021 ◽  
Author(s):  
Xavier Faïn ◽  
Rachael Rhodes ◽  
Philip Place ◽  
Vasilii Petrenko ◽  
Kévin Fourteau ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
High Resolution ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Absolute Calibration ◽  
Chemical Compositions ◽  
Accumulation Rates ◽  
Mixing Ratios ◽  
Enhanced Absorption

&lt;p&gt;Carbon monoxide (CO) is a regulated pollutant and one of the key components determining the oxidizing capacity of the atmosphere. Obtaining a reliable record of atmospheric CO mixing ratios since pre-industrial times is necessary to evaluate climate-chemistry models in conditions different from today. We present high-resolution measurements of CO mixing ratios from ice cores drilled at five different sites on the Greenland ice sheet which experience a range of snow accumulation rates, mean surface temperatures, and different chemical compositions. An optical-feedback cavity-enhanced absorption spectrometer (OF-CEAS) was coupled to continuous melter systems and operated during four analytical campaigns conducted between 2013 and 2019. The CFA-based CO measurements exhibit excellent external precision (ranging 3.3 - 6.6 ppbv, 1&amp;#963;), and achieve consistently low blanks (ranging from 4.1&amp;#177;1.2 to 12.6&amp;#177;4.4 ppbv). Good accuracy and absolute calibration of CFA-based CO records enable paleo-atmospheric interpretations. The five CO records all exhibit variability in CO mixing ratios that is too large and rapid to reflect past atmospheric mixing ratio changes. Complementary tests conducted on discrete ice samples demonstrate that such patterns are not related to the analytical process (i.e., production of CO from organics in the ice during melting), but very likely are related to in situ CO production within the ice before analyses. Evaluation of signal resolution and co-investigation of high-resolution records of CO and TOC show that past atmospheric CO concentration can be extracted from the records&amp;#8217; baselines at four sites with accumulation rates higher than 20 cm water equivalent per year (weq yr&lt;sup&gt;-1&lt;/sup&gt;). However, such baselines should be taken as upper bounds of past atmospheric CO burden. CO records from four sites are combined to produce a multisite average ice core reconstruction of past atmospheric CO for the Northern Hemisphere high latitudes, covering the period from 1700 to 1957 CE. From 1700 to 1875 CE, this record reveals stable or slightly increasing values remaining in the 100-115 ppbv range. From 1875 to 1957 CE, the record indicates a monotonic increase from 114&amp;#177;4 ppbv to 147&amp;#177;6 ppbv. The ice-core multisite CO record exhibits an excellent overlap with the atmospheric CO record from Greenland firn air which span the 1950-2010 time period. The combined ice-core and firn air CO history, spanning 1700-2010 CE, largely exhibits patterns that are consistent with the recent anthropogenic and biomass burning CO emission inventories. This brand new time series will be compared with the most recent results from Earth System Models involved in the CMIP6-AerChemMIP multi-model exercise.&lt;/p&gt;

scholarly journals Temperature and precipitation signal in two Alpine ice cores over the period 1961–2001

2014 ◽  
Vol 10 (3) ◽  
pp. 1093-1108 ◽  
Author(s):  
I. Mariani ◽  
A. Eichler ◽  
T. M. Jenk ◽  
S. Brönnimann ◽  
R. Auchmann ◽  
...  
Keyword(s):  
Meteorological Data ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Global Network ◽  
Proxy Data ◽  
Altitude Effect ◽  
Temperature And Precipitation ◽  
Precipitation Regimes ◽  
Combining Data

Abstract. Water stable isotope ratios and net snow accumulation in ice cores are commonly interpreted as temperature or precipitation proxies. However, only in a few cases has a direct calibration with instrumental data been attempted. In this study we took advantage of the dense network of observations in the European Alpine region to rigorously test the relationship of the annual and seasonal resolved proxy data from two highly resolved ice cores with local temperature and precipitation. We focused on the time period 1961–2001 with the highest amount and quality of meteorological data and the minimal uncertainty in ice core dating (±1 year). The two ice cores were retrieved from the Fiescherhorn glacier (northern Alps, 3900 m a.s.l.), and Grenzgletscher (southern Alps, 4200 m a.s.l.). A parallel core from the Fiescherhorn glacier allowed assessing the reproducibility of the ice core proxy data. Due to the orographic barrier, the two flanks of the Alpine chain are affected by distinct patterns of precipitation. The different location of the two glaciers therefore offers a unique opportunity to test whether such a specific setting is reflected in the proxy data. On a seasonal scale a high fraction of δ18O variability was explained by the seasonal cycle of temperature (~60% for the ice cores, ~70% for the nearby stations of the Global Network of Isotopes in Precipitation – GNIP). When the seasonality is removed, the correlations decrease for all sites, indicating that factors other than temperature such as changing moisture sources and/or precipitation regimes affect the isotopic signal on this timescale. Post-depositional phenomena may additionally modify the ice core data. On an annual scale, the δ18O/temperature relationship was significant at the Fiescherhorn, whereas for Grenzgletscher this was the case only when weighting the temperature with precipitation. In both cases the fraction of interannual temperature variability explained was ~20%, comparable to the values obtained from the GNIP stations data. Consistently with previous studies, we found an altitude effect for the δ18O of −0.17‰/100 m for an extended elevation range combining data of the two ice core sites and four GNIP stations. Significant correlations between net accumulation and precipitation were observed for Grenzgletscher during the entire period of investigation, whereas for Fiescherhorn this was the case only for the less recent period (1961–1977). Local phenomena, probably related to wind, seem to partly disturb the Fiescherhorn accumulation record. Spatial correlation analysis shows the two glaciers to be influenced by different precipitation regimes, with the Grenzgletscher reflecting the characteristic precipitation regime south of the Alps and the Fiescherhorn accumulation showing a pattern more closely linked to northern Alpine stations.

scholarly journals Snow Accumulation and Oxygen-Isotope Records at the Law Dome Summit, Antarctica (Abstract)

1988 ◽  
Vol 11 ◽  
pp. 220-220
Author(s):  
V. I. Morgan
Keyword(s):  
Oxygen Isotope ◽  
Isotope Ratio ◽  
Meteorological Data ◽  
Ice Core ◽  
Surface Profile ◽  
Correlation Coefficients ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Annual Layer ◽  
The Law

At the summit of Law Dome (66°44′S, 112°50′E) the annual snow accumulation is equivalent to 0.7 m of water, and seasonal cycles of oxygen-isotope ratio are preserved clearly in the firn. Isotope-ratio measurements on three 28 m deep ice cores taken 15 m apart near the summit show that although annual layer thicknesses are well correlated between the cores, the actual isotope values (even when averaged over several years’ accumulation) are poorly correlated.Since the three sites must obviously receive the same precipitation, the differences in isotope ratio imply that the amounts of the precipitation retained as accumulation from individual snow-falls throughout the year must vary. The large seasonal variation in isotope ratio then easily accounts for the offsets.In the Law Dome region, precipitation occurs mainly as a result of cyclonic activity in spring, winter and autumn. The stronger winds experienced at these times cause the snow to be formed into large dunes, which are the stable (although moving) surface configuration under these conditions. The movement of dunes by erosion on one face and deposition on the other causes the snow in them to be well mixed. Isotope measurements on a 0.7 m high dune on the inland ice cap showed that it was composed of “winter” snow, with an average isotope value of −28.2% and a range of only 1%. The harder underlying snow had values which varied between −24.2 and −27.4%.During periods of relatively calm or warm conditions the dunes become consolidated and their movement is greatly reduced. Further snow-falls then do not add accumulation to the top and up-wind side of the dunes but tend to fill them in on the down-wind side. In particular it is observed that for Law Dome the surface profile is quite rough in winter and spring, but the more gentle winds and light snow-falls experienced in summer produce a very smooth surface at the beginning of autumn, with all the surface hollows filled in.The ice-core isotope profiles confirm the evenness of the summer accumulation, compared to that of winter. Correlation coefficients are typically 0.26 for the winter minima and 0.65 for the summer peak in isotope ratio. This means that somewhat shorter averaging times can be used when compiling “climatic” records from isotope profiles if only the “summer” isotope values are used. This is useful in comparison of isotopic and meteorological data when only a limited time span is available.Apart from the short-term effects, which can be reduced as desired by longer averaging periods, these core studies also demonstrate how any process which can modulate the precipitation or accumulation will also affect the isotopic composition of the accumulated snow.

scholarly journals Accumulation variability derived from an ice core from coastal Dronning Maud Land, Antarctica

2004 ◽  
Vol 39 ◽  
pp. 339-345 ◽  
Author(s):  
Marzena Kaczmarska ◽  
Elisabeth Isaksson ◽  
Lars Karlöf ◽  
Jan-Gunnar Winther ◽  
Jack Kohler ◽  
...  
Keyword(s):  
High Resolution ◽  
Accumulation Rate ◽  
Ice Core ◽  
Austral Summer ◽  
Conductivity Measurement ◽  
Ice Cores ◽  
Electrical Conductivity Measurement ◽  
Regional Pattern ◽  
Dronning Maud Land

AbstractA 100 m long ice core was retrieved from the coastal area of Dronning Maud Land (DML), Antarctica, in the 2000/01 austral summer. The core was dated to AD 1737 by identification of volcanic horizons in dielectrical profiling and electrical conductivity measurement records in combination with seasonal layer counting from high-resolution oxygen isotope (δ18O) data. A mean long-term accumulation rate of 0.29 ma–1w.e. was derived from the high-resolution δ18O record as well as accumulation rates during periods in between the identified volcanic horizons. A statistically significant decrease in accumulation was found from about 1920 to the present. A comparison with other coastal ice cores from DML suggests that this is a regional pattern.

Intercomparison of firn core and meteorological data

2001 ◽  
Vol 13 (3) ◽  
pp. 329-337 ◽  
Author(s):  
Alison J. McMorrow ◽  
Mark A.J. Curran ◽  
Tas D. Van Ommen ◽  
Vin Morgan ◽  
Michael J. Pook ◽  
...  
Keyword(s):  
High Resolution ◽  
Abrupt Change ◽  
Meteorological Data ◽  
Chemical Species ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Meteorological Conditions ◽  
Depth Range ◽  
High Accumulation ◽  
Firn Core

High resolution firn core records of the oxygen isotope ratio (δ18O) and trace chemical species were extracted from a high accumulation site on Law Dome, East Antarctica. Inter-core comparisons were conducted and regional events identified in cores 5 km apart. High resolution dating of one of the firn cores was established using a co-located Automatic Weather Station (AWS) equipped with a snow accumulation sensor, allowing dating of individual precipitation events in the firn core record. Variations in the δ18O and trace chemical records were compared with meteorological conditions at the mesoscale and the synoptic-scale. Particular focus was given to an abrupt change in sea salt concentrations and δ18O within a depth range that appears from AWS accumulation data to have been deposited over a 24 hour period. The abrupt change in the firn core record was found to be consistent with an abrupt change in meteorological conditions. Direct comparisons between high resolution firn core records and meteorological conditions will greatly facilitate the interpretation of signals preserved in deep ice cores.

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