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Abstract. We present a 2700-year annually resolved chronology and snow accumulationhistory for the Roosevelt Island Climate Evolution (RICE) ice core, Ross IceShelf, West Antarctica. The core adds information on past accumulationchanges in an otherwise poorly constrained sector of Antarctica. The timescale was constructed by identifying annual cycles inhigh-resolution impurity records, and it constitutes the top part of theRoosevelt Island Ice Core Chronology 2017 (RICE17). Validation by volcanicand methane matching to the WD2014 chronology from the WAIS Divide ice coreshows that the two timescales are in excellent agreement. In a companionpaper, gas matching to WAIS Divide is used to extend the timescale for thedeeper part of the core in which annual layers cannot be identified. Based on the annually resolved timescale, we produced a record of past snowaccumulation at Roosevelt Island. The accumulation history shows thatRoosevelt Island experienced slightly increasing accumulation rates between700 BCE and 1300 CE, with an average accumulation of 0.25±0.02 mwater equivalent (w.e.) per year. Since 1300 CE, trends in the accumulationrate have been consistently negative, with an acceleration in the rate ofdecline after the mid-17th century. The current accumulation rate atRoosevelt Island is 0.210±0.002 m w.e. yr−1 (average since 1965 CE, ±2σ), and it is rapidly declining with a trend corresponding to0.8 mm yr−2. The decline observed since the mid-1960s is 8 times fasterthan the long-term decreasing trend taking place over the previouscenturies, with decadal mean accumulation rates consistently being belowaverage. Previous research has shown a strong link between Roosevelt Islandaccumulation rates and the location and intensity of the Amundsen Sea Low,which has a significant impact on regional sea-ice extent. The decrease inaccumulation rates at Roosevelt Island may therefore be explained in termsof a recent strengthening of the ASL and the expansion of sea ice in the easternRoss Sea. The start of the rapid decrease in RICE accumulation ratesobserved in 1965 CE may thus mark the onset of significant increases inregional sea-ice extent.
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Snow stratigraphy observations from Operation IceBridge surveys in Alaska using S and C band airborne ultra-wideband FMCW (frequency-modulated continuous wave) radar
Abstract. During the concluding phase of the NASA OperationIceBridge (OIB), we successfully completed two airborne measurementcampaigns (in 2018 and 2021, respectively) using a compact S and C band radarinstalled on a Single Otter aircraft and collected data over Alaskanmountains, ice fields, and glaciers. This paper reports seasonal snow depthsderived from radar data. We found large variations in seasonalradar-inferred depths with multi-modal distributions assuming a constantrelative permittivity for snow equal to 1.89. About 34 % of the snowdepths observed in 2018 were between 3.2 and 4.2 m, and close to 30 % of thesnow depths observed in 2021 were between 2.5 and 3.5 m. We observed snowstrata in ice facies, combined percolation and wet-snow facies, and dry-snow facies fromradar data and identified the transition areas from wet-snow facies to icefacies for multiple glaciers based on the snow strata and radarbackscattering characteristics. Our analysis focuses on the measured strataof multiple years at the caldera of Mount Wrangell (K'elt'aeni) to estimate the localsnow accumulation rate. We developed a method for using our radar readingsof multi-year strata to constrain the uncertain parameters of interpretationmodels with the assumption that most of the snow layers detected by theradar at the caldera are annual accumulation layers. At a 2004 ice core and2005 temperature sensor tower site, the locally estimated average snowaccumulation rate is ∼2.89 m w.e. a−1 between the years2003 and 2021. Our estimate of the snow accumulation rate between 2005 and2006 is 2.82 m w.e. a−1, which matches closely to the 2.75 m w.e. a−1 inferred from independent ground-truth measurements made the sameyear. The snow accumulation rate between the years 2003 and 2021 also showeda linear increasing trend of 0.011 m w.e. a−2. This trend iscorroborated by comparisons with the surface mass balance (SMB) derived forthe same period from the regional atmospheric climate model MAR (ModèleAtmosphérique Régional). According to MAR data, which show anincrease of 0.86 ∘C in this area for the period of 2003–2021, thelinear upward trend is associated with the increase in snowfall and rainfallevents, which may be attributed to elevated global temperatures. Thefindings of this study confirmed the viability of our methodology, as wellas its underlying assumptions and interpretation models.
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- Award ID(s):
- 1838236
- PAR ID:
- 10473878
- Publisher / Repository:
- The Cryosphere
- Date Published:
- Journal Name:
- The Cryosphere
- Volume:
- 17
- Issue:
- 1
- ISSN:
- 1994-0424
- Page Range / eLocation ID:
- 175 to 193
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/tc-17-175-2023
