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Chemical tracers of shelf derived waters in the Arctic Ocean

Chemical tracers of shelf derived waters in the Arctic Ocean. NABOS Cruise Aug. – Sept. 2013. Matthew B. Alkire Polar Science Center Applied Physics Laboratory University of Washington. Some useful chemical tracers. Salinity Iodine-129 d 18 O O 2 NO 3 NO 3 :PO 4. “Tracers” can

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Chemical tracers of shelf derived waters in the Arctic Ocean

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  1. Chemical tracers of shelf derived waters in the Arctic Ocean NABOS Cruise Aug. – Sept. 2013 Matthew B. Alkire Polar Science Center Applied Physics Laboratory University of Washington

  2. Some useful chemical tracers • Salinity • Iodine-129 • d18O • O2 • NO3 • NO3:PO4

  3. “Tracers” can help us to visualize and track changes in circulation of separate water types Carmack et al. (2008)

  4. 129I @ sfc 1990 Karcher et al (2012) Smith et al. (1998)

  5. 129I @ sfc 2004 Karcher et al (2012)

  6. RUSSIA USA Chukchi Sea East Siberian Sea Laptev Sea Kara Sea Greenland Barents Sea

  7. Shelf Processes Nutrient cycling Modify waters on the shelf River runoff Sea ice Chemical fingerprints Carbon & nutrient cycling Carmack & Wassmann (2006)

  8. Steele & Boyd (1998)

  9. H218O versus H216O Water column (18O:16O) ice = 3:1, 16O 16O 16O 18O sea ice 18O 18O 16O 16O 16O freeze 16O 16O 18O 18O seawater + brine 16O 16O 18O melt 18O 18O 18O 18O brine: negative d18O (16O rich) sea ice: positive d18O (18O rich) (18O:16O)water = 1:1, (18O:16O) water ~ 1:2, 16O > 18O isotopically light 18O > 16O isotopically heavy

  10. Where would you expect shelf waters to plot on this graph? Atlantic water Sea-ice melt ice melt ice formation/ brine release Meteoric water (precip., river runoff, glacial melt)

  11. Bauch et al. (2009)

  12. Bauch et al. (2009)

  13. 106 CO2 + 16 HNO3 + H3PO4 + 78 H2O = C106H175O42N16P + 150 O2 Advantage of O2 & NO3? Station 87°N, 180 (NPEO 2012)

  14. Can you identify the shelf water signature? Alkire et al. (2010)

  15. N2 fixation Mixing and/or convection? denitrification Redfield Air-sea exchange Station 87°N, 180 (NPEO 2012)

  16. Canada Basin, 2008 What’s going on here?

  17. NO = (9 x NO3) + O2 A minimum in NO has classically been used to identify lower halocline water Makarov Basin Amundsen Basin

  18. Jones et al. (2003)

  19. malkire@apl.washington.edu Questions? www.psc.apl.washington.edu North Pole Environmental Observatory

  20. Freshwater in the Arctic • River runoff • Pacific inflow through Bering Strait • Precipitation • Glacial melt • Groundwater

  21. Nishino et al. (2013)

  22. Itoh et al. (2007)

  23. Convective or “Fram Strait Branch” halocline water Advective or “Barents Sea Branch” halocline water Rudels et al. (2004)

  24. Cyclonic years Anticyclonic years Yamamoto-Kawai et al. (2005)

  25. How will this picture change in the future?

  26. What makes shelves special? • River runoff • Sea ice formation (e.g., polynyas) • Biological production • Organic matter respiration • Halocline formation • Mixing • Carbon

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