an analysis of russian sea ice charts for 1933-2006 a. mahoney, r.g. barry and f. fetterer national...
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![Page 1: An analysis of Russian Sea Ice Charts for 1933-2006 A. Mahoney, R.G. Barry and F. Fetterer National Snow and Ice Data Center, University of Colorado Boulder,](https://reader033.vdocuments.us/reader033/viewer/2022042718/56649f2c5503460f94c47bc1/html5/thumbnails/1.jpg)
An analysis of Russian Sea Ice Charts for 1933-2006
A. Mahoney, R.G. Barry and F. FettererNational Snow and Ice Data Center, University of Colorado
Boulder, Colorado, 80303, USA
AARI ice chart April 8-11, 2006
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Outline
• Introduction
• Background on AARI ice charts
• Method• Locating discontinuous pack ice edges
• Results• 20th Century sea ice extent variability
• Comparison with other data• Meteorological data• Other ice charts
• Summary and conclusions
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Introduction and
Background
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About the AARI* ice charts
• Operational sea ice charts generated approximately every 10 days, dating back as far as 1933
• Charts produced by assimilation of different observations:• satellite active / passive microwave• airborne radar and infrared• visual observations from aircraft, ships and coastal stations• coastal radar installations• buoy-mounted instrumentation• automatic ice stations
• Provide information on:• sea ice concentration• stages of development• ice forms
*Arctic and Antarctic Research InstituteSt Petersburg, Russia
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Airborne radar flightlines
• Standard pattern of airborne radar observations
• Carried out periodically through the year since 1970s
• Highest concentration along Northern Sea Route
From: Remote Sensing of the Sea
Ice in the Northern Sea Route, Studies and Applications,
Johannessen et al, 2007
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AARI ice charts in EASE grid
• Ice charts are provided in SIGRID* format and converted to EASE-Grid**
• Separate charts for eastern and western Russian Arctic
• Spatial and temporal coverage is variable and discontinuous
* Sea Ice Grid (World Meteorological Organization)**Equal Area Scalable Earth Grid – details at http://www.nsidc.org/ease
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Examples of early AARI ice charts
• Chart coverage is poor
• Mostly limited to reconnaissance flights within range of coastal stations
• Still possible to identify and locate the ice edge
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Method
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Coast-to-pole vectors
• 360 vectors along meridians from the coast to the pole
• Used for locating the edge of the pack ice
• Can cope with discontinuous edges
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Locating the edge of the pack ice
1) Transition to <15% ice concentration
2) Pack ice / landfast ice boundary
3) The coast
Algorithm looks for ice edge along every coast-to-pole vector
Ice edge is defined by either:
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Manual inspection of algorithm
• Algorithm can be confused around islands and polynyas
• In these cases, the edge is corrected manually
• The edge on every chart will be manually inspected
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Results
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Spatio-temporal coverage of results
• Only spring and summer months charted in early years
• Frequency of charts increases through record
• Continuity of ice edges improves over time
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Changes in sea ice extent
• Much regional variability
• Reduced autumn ice extent in early 20th century
• Increasingly negative anomalies in both spring and autumn since 1970s
• Missing data during key period (1993-1996)
Manually inspected
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Changes in sea ice concentration
• Comparison of decadal monthly means
• Increase from 1940s – 1970s is mostly matched by the loss between 1970s and 2000s
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Comparison with other
data
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Temperature and pressure anomalies
• Derived from station data North of 65°N
• Early and late part of record warmer than middle
• Evidence of decadal variability
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Ice and temperature variability
• No significant interannual correlation between ice and air temperature
• Adjacent seas show similar temperature trends, but different trends in ice extent
• Similarly weak relationship to station SLP observations
• No consistent correlations with Arctic Oscillation index
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Comparison with NIC* charts
• Overall mean difference is close to zero
• AARI charts report higher concentration in autumn and winter
• NIC charts report higher concentration in summer
• No apparent long-term differences though number of common cells between chart sets increases with time
* National Ice Center
AARI>
NIC
NIC>
AARI
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Summary
AARI ice charts provide a long timeseries of ice extent variability in Russian Arctic
• Manual inspection of ice edges required throughout record
Ice edge results so far indicate:
• Reduced ice extent in 1930s – 40s
• greatest reduction in Barents Sea
• Most evident in fall minimum extent
• Greater reduction in ice extent since 1970s
• Evident in both spring and autumn
Hi-latitude observations show cooling in mid 20th Century
• No direct correlations with ice extent variability
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Future work
Finish manual inspection of ice edgesFinish manual inspection of ice edges
More detailed analysis of sea ice variabilityMore detailed analysis of sea ice variability
• Both temporal and spatialBoth temporal and spatial
• Include landfast sea iceInclude landfast sea ice
• Statistical analysis of atmospheric forcingStatistical analysis of atmospheric forcing
Extend comparisons with other datasetsExtend comparisons with other datasets
• Derive an optimal, merged sea ice record from different Derive an optimal, merged sea ice record from different chartscharts
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AcknowledgementsVasily SmolyanitskyArctic and Antarctic Research Institute (AARI)St. Petersburg, Russia
• Providing the AARI data in SIGRID format with near-EASE-grid regridding software
Joey ComeauxNational Center for Atomspheric Research (NCAR)Boulder, Colorado, USA
• Assistance acquiring meteorological station data
NASA
• Award NNG04GH03G, “Twentieth Century Sea Ice Conditions in the Eurasian Arctic from a Comprehensive Reconstitution and Synthesis of Russian Data Sources with Modern Satellite Data”