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The Western Arctic Shelf-Basin Interactions (SBI) Project-Highlights 2006. SBI Arctic / global change project 2002-2004 map intensive field studies during the record summer sea ice retreat

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  1. The Western Arctic Shelf-Basin Interactions (SBI) Project-Highlights 2006 • SBI Arctic / global change project 2002-2004 map • intensive field studies during the record summer sea ice retreat • investigating production, transformation and fate of carbon at the shelf-slope interface in the northern Chukchi and Beaufort Seas • downstream of the productive shallow western Arctic shelves • prelude to understanding the impacts of a potential warming of the Arctic http://sbi.utk.edu

  2. Overview Statement • Pacific Water entering through the Bering Strait Gateway and across shelf and northward into the Arctic Basin: • is the most productive region in the Arctic • is undergoing the most significant environmental change (maximum ice retreat, potential ecosystem restructuring) • critical physical, biogeochemical and biological fluxes interact in this region, with ramification to the global system • the ice retreat and oceanic heat flux are unprecedented in the modern observational record being driven by both local and remote forcing • biologically-mediated carbon-transformation processes are critical to the regional carbon cycling and ultimately, to both regional and global carbon flux dynamics

  3. Climate Feedbacks Solar Insolation Humans Upper Trophics Global Circulation Examples of linkages between Shelf – Basin Interactions and the Arctic System Atmospheric Forcing Land-hydrology-sea interface Sea Ice Cover Bering Strait Inflow Shelf Carbon Cycle Shelf-Basin Exchange Carbon Storage

  4. Observed September sea ice extent 1979-2005 Significant and accelerated decrease in sea ice extent in the late 1990s and 2000s. Note that largest changes are at inflows of Pacific / Atlantic water into the Arctic Ocean and during SBI field programs. • Rate of decline • 1979-2001: 6.5 % per decade • 1979-2005: 8 % per decade 96-05 trend ~21% per decade? 09/05 09/87 09/02 • ARCSS relevant issues related to warming in the western Arctic Ocean • ecosystem change, including whale migration / feeding habit change • human aspects: native community subsistence and culture • increased human presence: new transportation routes, natural resource exploration • - potential global consequences of freshwater export from the Arctic Ocean

  5. Increased freshening of Pacific Inflow [Woodgate and Aagaard, GRL 2005] • moorings at Bering Strait: • decrease salinity and increase freshwater flux • revised Bering Strait FW influx upwards from 1989 • shelf-basin transport via advection, eddy formation, canyon transport

  6. Bering/Chukchi/Beaufort SeaMarginal Ice Zone System Fluxes of heat, salt, freshwater, nutrients through Bering Strait and their seasonal and inter-annual variability strongly influence the Western Arctic ecosystem [Woodgate et al. 2005; Clement et al. 2005] HV WHS EHS BC EB Modeled Sea Surface (0-5 m) Salinity (ppt), Velocity (cm/s) and Sea Ice Concentration (% - red contours) - Mean August 1979-1981 [courtesy W. Maslowski]

  7. Increased Pacific water heat fluxes into the Arctic Ocean Sheba EBC – Aug 2002 • Increased modeled northward heat flux off the Chukchi Shelf correlates with the recent ice retreat in the Western Arctic • (cor. coef. = 0.7-08) [Courtesy of W. Maslowski] - Heat content of surface waters: above 50 m depth sufficient to melt 0(10-100 cm) thickness of sea ice - Studies (both field and modeling) are needed to understand effects of Pacific Water advection from Bering Strait into the Arctic Ocean and its effect on the environment [SBI Hydrography Data Team (Codispoti, Swift et al.)] [Courtesy of W. Maslowski]

  8. Sediment-laden Sea Ice Multiple rafting with sediment layers in lower sections • >100,000 km2 of sediment-laden sea ice (5-8 x 106 t particulate export, highly significant for shelf budget) • Enhanced rafting due to changing sea-ice regime • Impact on ice primary production and carbon flux? Distribution of sediment-laden ice (fraction of total ice area) (data at: www.joss.ucar.edu/cgi-bin/catalog/sbi_hly-02-01/research/index) [Eicken et al. in 2005]

  9. Atmospheric Linkages Which storms trigger upwelling? NCEP reanalysis forwestern Arctic 22 upwelling events between September 2002 and May 2003! No upwelling Upwelling favorable Diagnosing an upwelling event in the western Arctic: Cross-stream fluxes of mass and properties [R. Pickart et al.]

  10. Primary production and optical findings in the SBI region • Barrow Canyon high productivity, reaching 8.8 g C m-2 d-1 • High particle export to slope, basin? System relevance: High levels of colored dissolved organic material (CDOM) were observed which would increase energy absorption in the surface waters by 40% over clearest natural waters thus impacting on heating, albedo impact and positive feedback to further ice melt [Hill and Cota, 2005] [E. Sakshaug 2004]

  11. Organic markers can detail carbon sources to the Arctic Basin • Bioavailable DOM is rapidly produced in shelf waters during spring  and summer and some of this DOM is transported to the basin - Rates of utilization of DOM are relatively low in shelf waters - Terrigenous DOM is abundant in shelf and polar surface waters - Terrigenous DOM discharged to the Arctic Ocean by rivers has a  modern radiocarbon age [Harvey, Belicka and Macdonald]

  12. Dissolved Organic Carbon (DOC) Cycling in the Western Arctic Annual fluxes Tg DOC CO2 2.7 2.5 7.3 Canada Basin 6.0 1.3 56 Tg DOC ? Terrestrial DOC new Marine DOC • DOC is being lost while circulating in the Arctic Ocean and/or • fluxes of DOC from river sources are being underestimated • DOC in the Arctic Ocean is probably not as refractory as previously thought, • and sediments are a potentially important source of DOC to the Arctic Ocean

  13. Pelagic-benthic coupling: SBI I and II results • Sediment community oxygen consumption (mmol O2 m-2 d-1) from 1984-2004 • an indicator of carbon supply to the underlying benthos, persistent patterns of carbon flux to sediments • yet time series stations in “hot spots” (black box) indicate decline in carbon supply and benthic standing stock [Grebmeier et al. 2006, Science] • Macrofaunal biomass (g C m-2) from 1977-2004 • identify “foot prints” of high carbon deposition and benthic biomass on the shallow continental shelves for time series investigations embedded in periodic process studies [Data maps from Grebmeier et al. 2006, Prog. Oceanogr., accepted]

  14. Zooplankton Grazing Impacts • Zooplankton grazing impacts are primarily dependant on zooplankton biomass, which increases in summer but is still low compared to other Arctic shelf regions • High primary production combined with low zooplankton grazing results in strong benthic-pelagic coupling that supports very high benthic biomass [Ashjian, Campbell, Plourde]

  15. Large Horizontal Export of POM at BC Barrow Canyon (BC) section • Much of the productivity occurring in this region of the Chukchi Sea shelf was: • exported laterally, with plumes of suspended POM in the upper halocline observed off-shelf extending into the Arctic Ocean basin (Bates et al., 2005), • or • vertically exported to the sea floor (Moran et al., 2005). UHW LHW LargePOC LargePON [Bates et al., 2005a; Moran et al. 2005]

  16. SBI Special Issue One - 23 papers Plan for SBI DSR 2nd volume-deadline fall 2006 (Eds. Grebmeier, Harvey and Stockwell)

  17. JOSS website statistics SBI Datasets:228 (+45) Data Type: Benthic 54 Hydrography 59 Ice 11 Meteorology 55 Microbiology 8 Mooring 3 Navigation 22 Optics 7 Plankton 10 Production 5 Satellite 23 Service – Bottle 21 Service – CTD 16 Underway 48 Water Chemistry 20 Cruise: 2004 HLY-04-02 12 HLY-04-03 10 HLY-04-04 4 HX-290 1(U) 2003 HLY-03-03 3 NBP03-04a 12 HX-274 1(U) 2003-14 Helo 0 2002 HLY-02-03 65 AWS-02-I 7 HX-260 1(U) HLY-02-01 63 Password Protected: 9 Phase I – 0 Phase II – 9 2002 Data – 1 Loaded < 1 yr – 4 CTD/Bottle – 7 Ship CD – 2 Phase: I 47 II 181 www.joss.ucar.edu/sbi

  18. SBI Phase III Planning Timeline • Mar. 2005: SBI Phase II and Phase III planning presentation made to ARCSS Committee; input requested (March 2006, Wash. DC) • Oct. 2005: discussions with NSF and ARCSS Committee about SBI Phase III, letter sent to AC • Nov. 2005: AC responds with support letter for SBI Phase III, plus guidance • Dec. 6, 2005: AGU informal evening meeting SBI Phase III planning • Dec. 19, 2005: SBI PI online meeting, discussions SBI II results & Phase III planning • Jan. 19, 2006: ARCSS Committee/SBI AC online meeting-Phase III planning • Jan. 30, 2006: Open Community eTown Hall Meeting: SBI update/Phase III • Feb. 9, 2006: letter from AC to SBI AC/PIs outlining their guidance for a SBI Phase III direction within the new ARCSS format • Feb. 22, 2006: Open Town Hall Meeting Phase III, Oceans Meeting, Honolulu, Hawaii • Feb. 26-28, 2006: Final SBI Phase II PI meeting • Mar. 6, 2006: SBI AC and ARCSS program managers at NSF • Mar. 29, 2006: SBI AC presentation to AC on Phase III direction, Seattle, WA • NSF AO: ? Separate SBI Phase III or within larger ARCSS AO; release planned summer 2006, proposal deadline fall 2006, funding 2007 during period of International Polar Year (IPY) 2007-2009

  19. ARCSS/SBI Phase IIIIntegration, Synthesis and Modeling ARCTIC CARBON CYCLING AND SHELF-BASIN DYNAMICS

  20. Overarching Themes and Questions • What are the important linkages between processes in the Western Arctic shelf-basin ecosystem(s) and the larger Arctic system? What are the ramifications for the global ocean and climate? • How will the large and interconnected changes recently observed in the western Arctic margins propagate through natural and human systems in the Arctic and sub-Arctic? How do these recent changes compare to the past? • 3. How does climate variability over multiple time scales influence the coupled physical, chemical, and biological processes over arctic shelf/basin systems? How do changes in these?

  21. Subthemes and Questions: • 1. Although the Western Arctic appears to play a disproportionately large role in the dynamics of pan-Arctic system, there is a growing need to integrate and synthesize data and processes linking climate forcing, element and heat fluxes through the Bering Strait gateway, and shelf / basin carbon cycling in the Western Arctic with the broader Arctic system. Relevant studies might include: •  Determine the most significant and critical changes to the Arctic system documented in the modern data records •  Investigate forcing connectivity by the atmosphere, land and ocean on shelf-basin exchange through a range of spatial and temporal scales •  Evaluate the impacts of seasonal sea ice extent and its variability on high productivity ecosystems, circulation, and shelf-basin interactions, and •  Understand how shelf-basin and inter-basin exchanges communicate change over larger Arctic system scales. •  How will the large and interconnected changes observed on the western Arctic shelf and margin affect and propagate through the larger Arctic and subarctic natural and human environment and how do they compare to past changes? •  How does climate variability over decadal to millennial scales influence oceanographic, biogeochemical, and biological processes over arctic shelf/basin systems, and how do these processes influence the broader arctic system?

  22. Subthemes and Questions: • 2. There is a dynamic barrier at the continental shelf /slope margin, resulting in sharp physical and biological gradients. Understanding the influence of the shelf break barrier on physical and biological processes is crucial for evaluating past system states and predicting future change impacts. Relevant studies might include: •  What processes maintain the sharp gradient between the most productive shelves adjacent to the least productive basin in the world’s ocean? •  How are shelf transformation products (salt, nutrients, carbon, zooplankton) fluxed across the shelfbreak into the basin? •  What processes on this productive shelf are critical for the tight benthic-pelagic coupling, which supports an incredible biomass of marine mammals that in turn are dependent upon by Native populations for their subsistence and cultural identity? •  How are these processes similar/different to continental margins in other arctic regions and/or continental margins in other regions of the world’s oceans? •  How will ongoing environmental changes modify the dynamic barrier between the shelf and basin?

  23. Subthemes and Questions: • 3. Variation in ice cover and thickness, mediated by solar insolation and advected heat flux through Bering Strait, initiate a local to system-wide cascade of changes in arctic physical and biogeochemical processes that are influenced strongly by oceanographic and biological processes over western Arctic shelves. Predicted future Arctic system changes include reduced sea ice, increased freshwater fluxes, higher air and sea temperatures, longer growing seasons, and permafrost thaw. Consequences of such changes will impact food web structure, trophic efficiency, sediment mineralization/sediment oxidation state, benthic biomass, and carbon export and sequestration into the Arctic Basin. Relevant research topics might include: •  How will the timing and extent of predicted future changes impact carbon cycling of the Arctic shelf system? •  How will the arctic system respond to ice retreat beyond the shelf break? •  What is the strength and variability of the linkages between important environmental controls of the arctic system (climate/physical oceanography) and ice cover, ocean biology and other elements of the arctic system (other dimensions)? •  How will these linkages change in the future? •  What are the consequences for the Arctic system (carbon, climate, human resource use)? • How will increased natural resource exploitation in the region impact shelf and slope ecosystem dynamics? • How will an increased flux of heat through Bering Strait influence clathrate erosion?

  24. Subthemes and Questions: • 4. Changing climate may alter the dynamics of pelagic and benthic arctic systems, with possible mode shifts in their structure and productivity. Relevant studies might include: •  How do changes in carbon cycling and pelagic-benthic coupling in the arctic system, driven by environmental change, influence the structure of arctic food webs and the population dynamics of important producer and consumer groups? •  How will these changes affect Native communities that depend on the current ecosystem state for their subsistence and cultural identity? •  How will future climate warming affect the production and export of carbon in arctic environments and the dynamics of arctic biological communities? •  How will bottom-up versus top-down controls of arctic biological systems respond to changing arctic ice and climatic conditions?

  25. Comments and suggestions?

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