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The role of sea ice in Arctic coastal dynamics and nearshore processes

The role of sea ice in Arctic coastal dynamics and nearshore processes. H. Eicken 1 , J. Brown 2 , L. W. Cooper 3 , T. C. Grenfell 4 , K. M. Hinkel 5 , A. Mahoney 1 , J. A. Maslanik 6 , D. K. Perovich 7 , C. Tweedie 8

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The role of sea ice in Arctic coastal dynamics and nearshore processes

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  1. The role of sea ice in Arctic coastal dynamics and nearshore processes H. Eicken1, J. Brown2, L. W. Cooper3, T. C. Grenfell4, K. M. Hinkel5, A. Mahoney1, J. A. Maslanik6, D. K. Perovich7, C. Tweedie8 1: GI-UAF, 2: WHOI, 3: DE&EB, UT, 4: DAS, UW, 5: DG, UCi, 6:CIRES, UCo, 7: CRREL, 8: DBPP, MSU • Introduction: The Arctic coastal zone as a large-scale multi-phase boundary • Far-field effects: Reduction in sea-ice extent, coastal erosion • Nearshore effects: - Sediment export by sea ice - Ice-push and break-out events - Bottomfast ice and coastal morphology • Conclusions: Changes in sea-ice regime enhance fluxes of energy and matter across coastal zone

  2. The Arctic coastal zone as a multi-phase boundary

  3. Changing ice cover Comiso, 2002

  4. Lengthening of open water season in coastal Alaska PB ice free PB <50% ice 100 80 60 Days 40 20 0 1960 1970 1980 1990 2000 Year (Prudhoe Bay navigation from Barnett’s Ice Index, National Ice Center)

  5. Increase in high-wind events and cyclone intensification in northern Alaska (Cassano et al.)

  6. Lengthening of OW season, ice retreat: Increased fetch & erosion? • Coastal change between 1948 and 1997 at Barrow, Alaska Lestak, Manley, Maslanik, Lynch, Buckley

  7. High spatial variability (erosionand aggradation) • Importance of episodic events • Short-term vs. long-term processes • Role of thermal subrosion and sea-ice processes Lestak, Manley, Maslanik, Lynch, Buckley

  8. Ice entrainment and export of sediments

  9. Sediment-laden sea ice off northern Alaska (May/June 2002)

  10. Preliminary results: Mean SPM in ice: 209 mg l–1 (7 core samples) Thickness of sediment-laden layers: 0.5 m Area of sediment-laden ice: 20 %, 100,000 km2 Total transport: 10.5 x 106 t Multiple rafting with sediment layers in lower sections

  11. Annual transport of sediment and organic carbon by sea ice Shown are best estimatesfor annual fluxes of - sea ice (in km3) - particulates transported by sea ice (in Tg = 106 t) - terrestrial organic carbon transported by sea ice (in Gg = 103 t) Maximum particulatetransport demonstratedfor individual iceentrainment events (LaptevSea): 18 Tg (18 x 106 t)

  12. Changes in the landfast ice regime Mahoney, unpubl.

  13. Winter sea-ice break-out events December 13, 2001: Ice breaks out from stretch of coastline SW of Barrow past NARL (>15 km) Photo: Craig George

  14. Ice push and ride-up events

  15. Ice push and ride-up events

  16. Bottomfast ice: Ice bonding and coastal morphology Reimnitz, 2002

  17. Changes in the bottomfast ice regime: Laptev Sea

  18. Changes in bottomfast ice regime

  19. Changes in bottomfast ice regime: Reduced ice thickness

  20. Conclusions: Changes in sea-ice regime enhance fluxes of energy and matter across coastal zone Decrease and thinning of sea ice cover with increased cyclone activity •Changes in sea ice regime result in substantially enhanced fluxes of heat, freshwater, particulates through the coastal zone • Ice-associated impacts include: (1) increased exposure to wave action during open water season with receding ice edge, (2) sea-ice entrainment and export of sediments in shallow water environments, (3) seafloor/coast-ice interaction through ice gouging and ice push events, (4) thermal subrosion and reduced ice-bonding in bottomfast ice zone, (5) larger scale land-ocean heat and moisture exchange

  21. Fast ice schematic

  22. Sea Ice Index Monitors Summer Minima • Last year’s minimum ice extent was a record low • Sept 2003 also low • Remarkably similar pattern both years • We attribute to large scale circulation patterns • anomalously warm southerly winds advecting ice poleward in spring • enhanced cyclonic activity in summer resulting in greater ice breakup and melting http://nsidc.org/data/seaice_index/ 2002 Fetterer, Serreze, Maslanik et al.

  23. 1 Feb 2002 3 Feb 2002 8 Feb 2002 18 Feb 2002

  24. Fast-ice morphology

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