chemical tracers of shelf derived waters in the arctic ocean matthew b. alkire polar science center...
Post on 16-Jan-2016
220 Views
Preview:
TRANSCRIPT
Chemical tracers of shelf derived waters in the Arctic Ocean
Matthew B. AlkirePolar Science Center
Applied Physics LaboratoryUniversity of Washington
NABOS CruiseAug. – Sept. 2013
Some useful chemical tracers
• Salinity• Iodine-129• d18O• O2
• NO3
• NO3:PO4
Carmack et al. (2008)
“Tracers” can help us to visualizeand track changes incirculationof separatewater types
129I @ sfc
Karcher et al (2012)Smith et al. (1998)
1990
129I @ sfc
2004
Karcher et al(2012)
Greenland
EastSiberianSea
LaptevSea
Kara Sea
BarentsSea
ChukchiSea
RUSSIAUSA
Shelf Processes
Carmack & Wassmann (2006)
River runoff
Sea ice
Carbon & nutrient cycling
Modify waters on the shelf
Nutrientcycling
Chemical fingerprints
Steele & Boyd (1998)
brine: negative d18O (16O rich)sea ice: positive d18O (18O rich)
16O16O 16O
16O
16O
18O 18O
18O18O
18O18O 18O
18O
16O
18O
18O
16O
16O16O
16O
sea ice
seawater + brine
(18O:16O)water = 1:1,
(18O:16O) ice = 3:1,
(18O:16O) water ~ 1:2,
Water column
freeze
melt
H218O versus H2
16O
16O > 18O isotopically light
18O > 16O isotopically heavy
Sea-ice melt
Meteoric water(precip., river runoff, glacial melt)
Atlantic water
ice melt
ice formation/brine release
Where would you expect shelf waters to plot on this graph?
Bauch et al.(2009)
Bauch et al.(2009)
Station 87°N, 180 (NPEO 2012)
Advantage of O2 & NO3?
106 CO2 + 16 HNO3 + H3PO4 + 78 H2O = C106H175O42N16P + 150 O2
Alkire et al. (2010)
Can you identify theshelf water signature?
Redfield
Air-sea exchange
denitrification
N2 fixation
Mixing and/or convection?
Station 87°N, 180 (NPEO 2012)
What’s going on here? Canada Basin, 2008
Makarov Basin
Amundsen Basin
NO = (9 x NO3) + O2
A minimum in NO has classically beenused to identify lower halocline water
Jones et al. (2003)
malkire@apl.washington.eduwww.psc.apl.washington.edu
North Pole Environmental Observatory
Questions?
Freshwater in the Arctic
• River runoff• Pacific inflow through
Bering Strait• Precipitation• Glacial melt• Groundwater
Nishino et al. (2013)
Itoh et al. (2007)
Convective or “Fram StraitBranch” halocline water
Advective or “Barents SeaBranch” halocline water
Rudels et al. (2004)
Cyclonic years Anticyclonic years
Yamamoto-Kawai et al. (2005)
How will this picture change in the future?
What makes shelves special?
• River runoff• Sea ice formation
(e.g., polynyas)• Biological production• Organic matter
respiration
• Halocline formation• Mixing• Carbon
top related