Southeastern Alaska, encompassing theglaciated Chugach-St. Elias range (Figure 1), isone of the premier locations where tectonics,orogenesis, glacial erosion, landscape modifi-cation, and continental margin sedimentationcan be studied in unison, allowing for quanti-tative models to be developed linking thissuite of processes [e.g., Jaeger et al., 2001].This area is an exceptional natural laboratoryfor studying a range of geologic problems(Figures 2 and 3), including the links betweenorogenic processes and continental accretion,glacial landscape modification, and sedimen-tation.

Geologic processes operate at rapid ratesalong the margin, which allows concurrentdata collection on tectonic deformation,uplift,erosion, and sedimentation and developmentof comprehensive geodynamic models con-necting these diverse processes.The activeprocesses in southeastern Alaska are compa-rable or significantly greater than those studied inthe Himalayan orogeny,and include extremelyhigh sediment yields, active faults associatedwith mountains and valley glaciers,and orogenycoinciding with extensive glacial cover.

An important advantage of Alaska is theproximity of the highest coastal mountain rangeon Earth to an energetic ocean with essentiallyno intervening basins to trap sediment.Tectonicsignals are therefore quickly recorded in off-shore basins with little signal modificationresulting from long transport in rivers or tem-porary storage.

Due to the variety of climatic and tectonicprocesses that interact through the orogenesisof a glacially dominated coastal mountain beltsuch as the St. Elias range, a wide scope ofexpertise and techniques are required to pro-duce a fundamental leap forward in ourunderstanding of such systems.

To that end, a science plan has been assem-bled by attendees of a workshop,funded jointlyby the U.S. National Science Foundation-

Continental Dynamics program and the JointOceanographic Institutions-U.S.Science SupportProgram, which was held in Austin,Texas, 4–6May 2003.This plan (which can be downloadedfrom: http://web. clas.ufl.edu/users/jaeger/JOI_CD/index2.htm) stems from the advice ofthe 57 workshop attendees, plus additionalresearchers interested in using the southeasternAlaska region (i.e.,coastal mountains,continentalmargin,Gulf of Alaska abyssal plain) as a naturallaboratory to study tectonic-climatic interactionsin a glacial environment.

The science plan—written by members of thediverse communities of ocean drilling,glaciology,tectonophysics, and climate dynamics—sum-marizes the state of knowledge of relevant topics,provides a list of detailed scientific questions,and contains suggestions for implementation.By bringing together such a diverse group ofEarth scientists, it was possible for the first

time to outline the issues associated with gapsin our understanding of the linkages betweenlate Cenozoic collisional tectonics and climatein Alaska and the northeastern Pacific Ocean.

This article summarizes the science plan.

Scientific Questions

The science plan organizes important goalsin the Gulf of Alaska for evaluating tectonic-climatic cooperation into four broad topicalresearch questions of potentially globalimportance:

1.What are the three-dimensional kinematicand dynamic processes of oblique microplateaccretion/plateau subduction, and what arethe implications for continental growth?

2.What have been the critical Neogene climaticshifts in the high-latitude Pacific, and whatwere the consequences for northern hemisphereclimate,glaciation,and environmental change?

3.At what temporal and spatial scales doesorogenesis influence global climate, and howdo major glacial fluctuations shape orogenesis?

4. How can this natural laboratory with itsactive tectonics, abundant geologic hazards,aggressive glacial processes, and dramaticlandscape be used for geoscience educationand outreach?

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26 OCTOBER 2004

PAGES 433–448

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EOS,TRANSACTIONS, AMERICAN GEOPHYSICAL UNION

PAGES 433, 438–439

Examining Tectonic-ClimaticInteractions in Alaska and the Northeastern Pacific

Fig.1.Photograph taken from Icy Bay showing Mount St. Elias towering 5.5 km above the coastline of the Gulf of Alaska with a tidewater glacier reaching the bay in the foreground.

BY S. GULICK, J. JAEGER, J. FREYMUELLER, P. KOONS,T. PAVLIS,AND R. POWELL

Eos,Vol. 85, No. 43, 26 October 2004

Why Southeastern Alaska?

Several key points are raised as to whysoutheastern Alaska provides such an excel-lent setting for insight into these four globalquestions.Tectonically, it can serve as a modernanalog for processes that have constructedmuch of the continental crust through terraneaccretion.The margin encompasses a subduc-tion to strike-slip transition that is observableboth onshore and offshore, allowing imagingof crust-mantle interaction at such transitions.This plate boundary has generated the second-largest historical earthquake (1964), the largesthistorical tsunami (1958), the largest area ofcoseismic uplift (1964), and the greatest docu-mented coseismic uplift (14.2 m in 1899). Pre-sent tectonic convergence rates are 2–3 timesas high as in the Himalaya and are comparableto the total convergence between India andEurasia.

Climatically, the area includes the oldest andthickest northern hemisphere Cenozoic glacialrecord,and studies in this region can illuminatethe currently poorly constrained history of theCordilleran ice sheet,potentially including itsinitiation,and its significance for global climatedynamics.The expanded Neogene marine andglacial sedimentary record within the NorthPacific can enhance other high-latitude climaterecords.The Gulf of Alaska is a prime site forassessing the history of Holocene (or longer)decadal-scale (e.g., Pacific Interdecadal Oscil-lation or PDO) climate change, both geograph-ically and due to high sediment volumesproducing very high resolution paleoclimaterecords. Finally, there is an opportunity to con-strain the Late Quaternary marginal marineenvironment to assess the feasibility of pre-his-torical human coastal migration routes.

The Chugach-St.Elias range is a mini-orogenywhere tectonic and climatic processes andtheir interactions may be studied at a tractable

scale.The landscape is sculpted primarily byglacial processes that produce the highestglobal glacial denudation rates (over 101 mma-1) and in turn provide record high sedimentaccumulation rates allowing for very high res-olution proxy sedimentary records.This mar-gin is the type location for temperate glacimarinesystems and their models, and a unique ~5-km-thick sedimentary record of depositionrecording at least 6 Ma of tectonic and climaticinteraction is present.Because of the relativelyconfined and closed source-to-sink depositionalsystem, there may be little lag between sedi-ment production and marine accumulation.Tectonically, observable deformation patternsin oblique convergent settings may reflect cli-matic influences.The tectonic setting,Neogenestratigraphy and sedimentary processes,glacialmass-balance,and structural and metamorphichistory are reasonably well characterized,whichallows for development of integrated experi-ments in tectonic and climatic interaction.

Purpose and Interactions

The science plan is intended to assist in pro-posal preparation and evaluation for futureGulf of Alaska studies,and practitioners of thenumerous techniques summarized the keymeasurements necessary for addressing thescientific questions. Opportunities for educa-tion and outreach including “teacher in thefield”programs,interactions with National Parks,and Native American nations were discussed.This research initiative also has strong links toseveral programs beyond IODP and NSF-fund-ed core research, including Earthscope, ICE-Sat, Marine Aspects of Earth System History(MESH),U.S.GLobal Ocean Ecosystems Dynamics(U.S. GLOBEC), Community Surface DynamicsModeling System (CSDMS), River-DominatedOcean Margins (RiOMar), the Mt. Logan Ice

Coring Project, Paleoenvironmental Arctic Sci-ences (PARCS), Past Global Changes (PAGES-IGBP), and Study of Environmental ArcticChange (SEARCH).

Implementation Phases

Because of the far-reaching scope of theissues raised in this science plan, it is not pos-sible to create a comprehensive implementa-tion plan.Instead,a general list of recommendedtasks have been grouped into three implemen-tation phases that reflect logistical concernsand the need to address the most glaring gapsin knowledge and data.

Phase 1

Developing and maintaining a Gulf of Alaskaresearch Web site and an Alaska GIS databasefor integration of emerging interdisciplinarydata sets is a high priority. Because of the out-reach potential, all future field and laboratoryprojects should have a strong outreach com-ponent from the beginning of the programwith Web sites identified and accessible to K-12 education.

Particular Phase 1 experiments should includethe acquisition of both high-resolution andregional marine seismic reflection surveys toadequately understand the regional sedimen-tary budget, examine the offshore tectonicdeformation, and plan for future IODP drilling.

A comprehensive suite of very high resolu-tion paleoclimatic, paleoceanographic, andpaleoecological studies on cores from themargin will establish proper chronometersand a series of climate proxies leading to anunderstanding of the Quaternary climatic his-tory that can be later extended into the Neo-gene through ocean drilling and terrestrialoutcrop sampling.

A GPS array should be installed rapidly toensure a sufficiently long period of observa-tion to exceed 1 mm a-1 horizontal and 2 mma-1 vertical precision. Existing monitoring sur-veys of glacial and fluvial mass fluxes shouldbe maintained and expanded to ensure conti-nuity of records in an aim to capture transientsin mass flux.

Expansion of modern automated meteoro-logical arrays is important for constructingsufficiently long climate time series that per-mit integration of records from high-altitudeice core sites to sea level marine records.Establishment of a passive seismic monitoringarray will be necessary for imaging crustaland upper mantle velocity structure and eval-uating seismic hazards.A modeling programshould be initiated to aid in sampling strategies,to investigate cooperation among systems,and to develop numerical strategies for han-dling the nonlinear interactions in the climat-ic-tectonic system.

Phase 2

The collection of the initial data sets in Phase1 will allow for the refinement of experimentsthat can investigate stratigraphic, structural,and petrologic processes and relationships to

Fig.2.Gulf of Alaska region: geography and location of previous DSDP and ODP drilling locations(see inset).Composite of MODIS images (taken at different times) for southern Alaska courtesy of MODIS Rapid Response Project at NASA/GSFC.Shaded bathymetry is from ETOPO2 global elevation data. Inset map shows overall location.

examine orogenic history, mass flux, and climate interactions through the system.A geochronological framework should bedeveloped early in Phase 2 to identify trendsin local kinematics using low- and high-tem-perature thermochronology, cosmogenic dating, detrital thermochronology, fluid inclu-sion,and geological studies.To constrain thespatially varying tectonic geometry, an activeseismic study of crustal architecture shouldbe conducted onshore and offshore to collecttwo-dimensional and three-dimensionaltomography.Aerogeophysical,marine geophys-ical, and remote sensing programs need to beinitiated to determine the gravity field, icethickness,and integrated topographic-bathymetricsurface to serve as baseline data for repeatsurveys that monitor temporal changes. Geo-metric information from seismic studies andmass flux data should be used to condition,test,and develop the numerical models focused

on kinematics,denudation, sediment transport,and storage.

Phase 3

Repeat marine and aerogeophysical, andsatellite-based remotely sensed surveys toexamine landscape evolution should beacquired. Repeat surveys of GPS arrays wouldprovide additional information on local velocityfields. Offshore IODP drilling from fjords todeep-sea fans will examine the integrated tec-tonic-climatic history of the margin.Drillingbuilds on all previous geophysical, geological,ecological, climatic, and modeling efforts toenhance an integrated picture of the coopera-tion between climate and tectonic processes.

Conclusion

While these recommendations are wide-ranging and ambitious, it is through the

proposed targeting of the southeastern Alaskanatural laboratory with a broad range of tech-niques to study a series of dynamic but inter-related processes that will allow significantadvancement in our understanding of conti-nental dynamics, glacial-interglacial climate,and their interactions.The process has alreadybegun,as some of these recommended studieshave been proposed and recommended forfunding by NSF.

Acknowledgments

The authors thank the attendees of the Tec-tonics and Climate in Alaska workshop inAustin,Texas, and the contributors to the sci-ence plan.This workshop, which the scienceplan and this article grew out of,was sponsoredby NSF Continental Dynamics and Joint Oceano-graphic Institutions,Inc.The efforts of Judy Jacobsand an anonymous reviewer are appreciated.This article is UTIG Contribution 1705.

References

Jaeger, J. M. et al. (2001), Orogenic and glacialresearch in pristine southern Alaska, Eos,Trans.,AGU,82 (19), 213, 216.

Plafker, G. (1987), Regional geology and petroleumpotential of the northern Gulf of Alaska continentalmargin, in Geology and Resource Potential of theContinental Margin of Western North America andAdjacent Ocean Basins, Earth Sci. Ser., vol. 6, editedby D.W. Scholl,A. Grantz and J. G.Vedder, pp. 229-268,Circum-Pacific Counc. for Energy and Miner.Resour., Houston,Tex.

Plafker, G., J. C. Moore, and G. R.Winkler (1994), Geol-ogy of the southern Alaska margin, in The Geologyof Alaska, volume G-1,edited by G.Plafker and H.C. Berg, pp. 389–449, Geol. Soc. of Am., Boulder,Colo.

Author Information

Sean Gulick, University of Texas,Austin; JohnJaeger, University of Florida, Gainesville; JeffFreymueller, University of Alaska, Fairbanks; PeterKoons, University of Maine, Orono;Terry Pavlis,University of New Orleans, La.; and Ross Powell,Northern Illinois University, DeKalb

For additional information or a printed version ofthe science plan, contact Sean Gulick at sean@ig.utexas.edu,or John Jaeger at jaeger@geology.ufl.edu.

Eos,Vol. 85, No. 43, 26 October 2004

Fig.3.Tectonostratigraphic terranes and structural features of southern Alaska and adjacent Gulfof Alaska.Modified from Plafker [1987] and Plafker et al. [1994].