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An analysis of Russian Sea Ice Charts for 1933-2006. AARI ice chart April 8-11, 2006. A. Mahoney, R.G. Barry and F. Fetterer National Snow and Ice Data Center, University of Colorado Boulder, Colorado, 80303, USA. Outline. Introduction Background on AARI ice charts Method

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An analysis of russian sea ice charts for 1933 2006

An analysis of Russian Sea Ice Charts for 1933-2006

AARI ice chart April 8-11, 2006

A. Mahoney, R.G. Barry and F. Fetterer

National Snow and Ice Data Center, University of Colorado

Boulder, Colorado, 80303, USA


Outline

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


Introduction and background

Introduction and Background


About the aari ice charts

About the AARI* ice charts

*Arctic and Antarctic Research Institute

St Petersburg, Russia

  • 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


Airborne radar flightlines

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


Aari ice charts in ease grid

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


Examples of early aari ice charts

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


Method

Method


Coast to pole vectors

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


Locating the edge of the pack ice

Locating the edge of the pack ice

Ice edge is defined by either:

  • Transition to <15% ice concentration

  • Pack ice / landfast ice boundary

  • The coast

Algorithm looks for ice edge along every coast-to-pole vector


Manual inspection of algorithm

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


Results

Results


Spatio temporal coverage of results

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


Changes in sea ice extent

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


Changes in sea ice concentration

Changes in sea ice concentration

  • Comparison of decadal monthly means

  • Increase from 1940s – 1970s is mostly matched by the loss between 1970s and 2000s


Comparison with other data

Comparison with other data


Temperature and pressure anomalies

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


Ice and temperature variability

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


Comparison with nic charts

Comparison with NIC* charts

AARI

>

NIC

NIC

>

AARI

* National Ice Center

  • 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


Summary

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


Future work

Future work

  • Finish manual inspection of ice edges

  • More detailed analysis of sea ice variability

  • Both temporal and spatial

  • Include landfast sea ice

  • Statistical analysis of atmospheric forcing

  • Extend comparisons with other datasets

  • Derive an optimal, merged sea ice record from different charts


Acknowledgements

Acknowledgements

  • Vasily Smolyanitsky

  • Arctic and Antarctic Research Institute (AARI)

  • St. Petersburg, Russia

  • Providing the AARI data in SIGRID format with near-EASE-grid regridding software

  • Joey Comeaux

  • National 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”


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