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Why are the Great Alaskan Tidewater Glaciers Advancing During the MWP - Controls on Tidewaters - Relevance to SLR - The chronology of advance and Medieval.

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Presentation on theme: "Why are the Great Alaskan Tidewater Glaciers Advancing During the MWP - Controls on Tidewaters - Relevance to SLR - The chronology of advance and Medieval."— Presentation transcript:

1 Why are the Great Alaskan Tidewater Glaciers Advancing During the MWP - Controls on Tidewaters - Relevance to SLR - The chronology of advance and Medieval Climate along GOA - Possible reasons GSA - Houston 2008 Acknowledgements: The College of Wooster, NSF, NPS, NGS, Keck Geology Consortium, USGS and INSTAAR for the great photos. Greg Wiles, Dan Lawson, Tom Lowell, Dave Barclay Pfeffer, 2007

2 Wrangell/ St. Elias Mountains Kenai Mountains Chugach Mountains 50 km Wrangell- St. Elias Gulf of Alaska Locations - Southern Alaska Kenai Peninsula Alaska

3 Why is Sea Level Rising? - the top 3 reasons 1 2* 3 IPCC - AR

4 Meier et al., 2007 Most of the Ice from Small Glaciers is in Alaska

5 Columbia Bay (T. Pfeffer)(Pfeffer et al., 2008)

6 Northwestern Glacier - Kenai Fjords National Park McCarty Northwestern McCarty

7 Columbia Glacier has undergone 15 km of retreat since ~1982.

8 Field (1941)Molnia (2004) Glacier Bay National Park and Preserve - Muir Glacier

9 Tidewater Glacier Cycle (Post, 1975)

10 = sediment

11 Controls on Calving Glacier Climate - summer temperature/ winter precipitation Fiord geometry Water depth Sediment supply to glacier snout Anderson 2006

12 30 km left 350 m = water depth trimline Calving front icebergs Columbia

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14 Dendrochronology and Dendroclimatology

15 Forest Glacial History Forest Response

16 Columbia Bay - Kill Site AD 1770 AD 1810

17 Crossdated logs and Land-terminating record MWP

18 Tree Ring Dates along Columbia Bay ~1000 year advance ~10s retreat Austin was right

19 Glacier Bay National Park and Preserve Greatest uplift in the world ~1cm of the 20 rise is from GB Multiple advance and retreat during the Holocene AD 850

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21 Multiproxy Comparisons Glaciers = Summer Temperature ? TR Indices MWP LIA

22 Structure of the Warming Decadal variability Is strong

23 Sorting Out Climate and Dynamic Controls: Climate Variability Long-term - 10s-100s thousands of years 1,000 years 100 years Pacific Decadal Variability (PDV)

24 Columbia Glacier and Summer Temperature advance pause at midfiord? advance

25 Tidewater Glacier Cycle (Post, 1975)

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27 Tidewater Glaciers GSA Houston 2008 Alaska tidewater glaciers continue to lose mass and flux to the sea During the MWP many were advancing - forced by tributary valley sediment contributions along with increased precipitation and decadal variability Sorting out the dynamic and climatic controls over century to millennia is ongoing but it may be related to precipitation as it affects sediment flux Pfeffer - Columbia Bay


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