Light-matter%20interactions%20in%20the%20Arctic%20Ocean:%20Use%20of%20ocean%20color%20remote%20sensing%20the%20monitor%20and%20assess%20the%20effect%20of%20climate%20change

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Light-matter interactions in the Arctic
OceanUse of ocean color remote sensing the
monitor and assess the effect of climate change

• Marcel Babin1 Simon Bélanger2

1 Laboratoire dOcéanographie de Villefranche,
France 2 Université du Québec à Rimouski, Canada
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Relevant Facts

• Temperature has risen twice faster in the Arctic
  than in other regions air temperature is
  expected to increase by up to 7C during the next
  century
• Permafrost, which represents 25 of the
  continental surface of the northern hemisphere,
  has been observed to have undergone a temperature
  increase since the 1960s and, in many places, to
  gradually thaw
• From 1936 to 1999, an increase of 7 was observed
  for river discharge to the Arctic Ocean

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Relevant Facts

• Temperature has risen twice faster in the Arctic
  than in others regions air temperature is
  expected to increase by up to 7C during the next
  century
• Permafrost, which represents 25 of the
  continental surface of the northern hemisphere,
  has been observed to have undergone a temperature
  increase since the 1960s and, in many places, a
  gradual thaw
• From 1936 to 1999, an increase of 7 was observed
  for river discharge to the Arctic Ocean
• The summer ice cover over the Arctic Ocean
  decreased by 20 since 1979 it is predicted that
  it will disappear almost completely by the end of
  the century

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Stroeve et al. (2007) GRL
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Relevant Facts

• Temperature has risen twice faster in the Arctic
  than in others regions air temperature is
  expected to increase by up to 7C during the next
  century
• Permafrost, which represents 25 of the
  continental surface of the northern hemisphere,
  has been observed to have undergone a temperature
  increase since the 1960s and, in many places, a
  gradual thaw
• From 1936 to 1999, an increase of 7 was observed
  for river discharge to the Arctic Ocean
• The summer ice cover over the Arctic Ocean
  decreased by 20 over the last 26 years it is
  predicted that it will disappear almost
  completely by the end of the century
• The amount of atmospheric ozone above the Arctic
  during the spring, has decreased by 10 to 15
  since 1979

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One may expect that

1. An increasing fraction of the organic carbon
   sequestered into the permafrost will be
   transported toward the Arctic Ocean together with
   inorganic nutrients
2. The Arctic Ocean surface layer will increasingly
   be exposed to light, including UV
3. The organic matter of terrestrial origin will be
   oxidized to CO2 both through photo-oxidation, and
   bacterial activity amplified by light
4. Photosynthesis will be increasingly stimulated by
   light and inorganic nutrients, and will lead to
   more carbon sequestration

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And wonder whether

• The Arctic Ocean will become a new net source of
  CO2 originating from organic carbon that was
  sequestered in the permafrost (analogous to the
  combustion of fossil fuel), or a stronger
  biological sink of CO2 leading to more
  sequestration of carbon in the sediments

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Three major processes responsible for carbon
fluxes, that are sensitive to light

• Primary production
• CDOM photo-oxidation
• Bacterial activity

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Primary Production over the Arctic Ocean

• Preliminary results obtained using the Globcolour
  data set

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The Model
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The Model
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Calculation steps
SBDART ISSCP (qs, tcloud, ?cloud?, ozone)
Globcolour Lw(l) ChlGSM
Chl
af(l)
Kd(l)
Ed(l,0,t)
Ed(l,z,t)
PUR(z,t)
KPUR
PP model
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Attempts to retrieve ?chl a?
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Attempts to retrieve ?chl a?
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Attempts to retrieve ?chl a?
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Attempts to retrieve af(443)
QAA
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PP Model Result
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PP Model Result
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Previous estimates of Arctic PP
Latitude criterion This study Antoine et al. (1996) Behrenfeld Falkowski (1997) Longhurst et al. (1995)
gt50 5.4
gt60 2.5
gt70 1.0 0.6 0.4 1.4
Gt C y-1
Sakshaug (2004) ? 1.5 Gt C y-1
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Follow-up

• QC of all intermediate products
• Examine the quality of atmospheric corrections
• Implement the detection of pixels contaminated by
  ice adjacency (Bélanger, Enh Babin 2007)
• Account for pixels partially covered by ice
• Improve the parameterisation of the P vs. PUR
  relationship
• Determine the impact of undocumented pixels (qs
  too high)

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CDOM Photo-oxidation in the Beaufort Sea

• Use of the SeaWIFS data set

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CDOM Photo-oxidation
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Photo-oxidation in the Beaufort Sea
Bélanger et al. (GBC 2006)
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Photo-oxidation in the Beaufort Sea
Calculation steps

• Daily calculation of incident irradiance in the
  UV and visible based on aerosol, cloud and ozone
  data from TOMS observations, and on ice data from
  SMMR/SSMI
• fDIC values measured in situ
• aCDOM at constant of from SeaWiFS observations

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Bélanger et al. (GBC 2006)
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Bélanger, Babin Larouche (JGR, in press)
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Bélanger (2006)
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Bélanger (2006)
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Bélanger, Babin Larouche (JGR, in press)
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Bélanger et al. (GBC 2006)
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Bélanger et al. (GBC 2006)
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Relative importance of Photooxidation
tDOC from the Mackenzie 1 300 Gg C y-1
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Relative importance of Photooxidation
to tDOC photomineralization
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End