Typhoon Kaitak on 2005

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Typhoon Kaitak on 2005
Nov. 8, MODIS 250m RGB
Nov. 5, MODIS Chl-a
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Upper Ocean Responses to Typhoon Meari Passage in
The East China Sea Revealed from Argo Float and
Multiplatform Satellites Siswanto, E., J.
Ishizaka, K. Tanaka, K. Okamura, A.
Kristijono Submitted to GRL
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Background

• The facts have been known
• Primary production enhancement following typhoon
  passage is caused by preceding ocean physical
  responses (e.g., upwelling, entrainment),
• It has been speculated that
• While global warming may intense typhoon
  activity, typhoon itself may have potency to
  reduce atmospheric carbon dioxide through
  typhoon-driven biological pump,
• Some information have not been understood
• The coupling of ocean physical and biological
  changes in response to typhoon passage, by which
  some part of biological production enhancement
  might be exported out of euphotic zone,
• To what degree typhoon might contribute to annual
  carbon export in the ECS.

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Typhoon Meari Track Overlaid on Bathymetric Map
of The East China Sea
Argo float positions
Hydrographic stations

• Historical Hydrographic Data
• 2 stations from JODC (October 1988)
• 1 station from SNFRI (September 1988)

• Satellite Data
• SeaWiFS Chl-a
• SeaWiFS PAR
• TRMM/TMI SST

• Argo Float Data
• Argo float ID 29000363
• (http//www.usgodae.org)
• Pre-Typhoon Meari dates 20 24 Sep 04
• Post-Typhoon Meari dates 28 Sep 2 Oct 04

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Surface Ocean Responses to Typhoon Meari Passage
VGPM-based Primary Production
SeaWiFS Surface Chlorophyll-a
Merged Satellite Surface Height Anomaly
TRMM/TMI Sea Surface Temperature
Pre-typhoon
Post-typhoon

• Upwelling is indicated by
• Decreasing SHA from 1.83 cm to -20.13 cm,
• Decreasing SST from 28.5 oC to 23.9 oC.

• Upwelled nutrients enhanced
• Chl-a from 0.2 mg m-3 to 1.05 mg m-3,
• PP from 551 mg C m-2 d-1 to 1596 mg C m-2 d-1

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Chl-a Bloom Peak and Intense Cooling Time Lags to
Typhoon Passage

• Intense sea surface cooling (28 Sep) lagged
  Typhoon Meari passage within 1 day,
• But Chl-a bloom peak (30 Sep) manifested at least
  3 days after Typhoon Meari passage indicating
  Chl- a bloom resulted from new production
  stimulated by upwelled nutrients,
• Chl-a bloom (30 Sep) was wider or more remarkable
  on the left side of Typhoon Meari track due to
  some factors such as shallower nitracline depth
  on the shelf region than that on the offshelf
  region, landward movement of Kuroshio subsurface
  water that may also induce upwelling over the
  shelf etc.

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Vertical Profiles Changes in Responses to Typhoon
Meari Passage
28 Sep
T dropped by 3.6oC
2 Oct
28 Sep
Depth (m)
Latitude (oN)
24 Sep
27 Sep
20 Sep
S increased by 0.38
26 Sep
Longitude (oE)
T (oC)
S
NO3-N 0.094 T2 5.346 T 76.089
NO3-N increased by 1.47 µM
NO3-N (µmol l-1)
Depth (m)
20 September (pre-typhoon)
24 September (pre-typhoon)
Sig-t increased by 0.84
28 September (post-typhoon)
2 October (post-typhoon)
T (oC)
NO3-N (µmol l-1)
Sigma-t
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Estimating NO3-N Increase and New Production (NP)
Within Euphotic Zone Over Chl-a Bloom Area With
TRMM/TMI SST as Input
Employing NO3-N profile model as NO3-N
vertical profile parameters 1. Nitracline Depth
(ND) 16.11 exp(0.047 SST) 2. Exponent
1.425E-7 exp(0.464 SST) 3. Slope -0.007 SST
0.242 From 0 m to 30 m depth NO3-N(z) 0.094
SST2 5.346 SST 76.089 From 31 m to
ND NO3-N(z) NO3-N(30) exp (exponent(z-30))
From (ND1) m to Euphotic Depth (Zeu) NO3-N(z)
NO3-N(ND) slope (z ND) Where z
depth Zeu (4.6/(0.047 0.063 Chl-a))

• NO3-N increase was 1.82.2 Gg N
• NP was 12.1 14.3 Gg C

• F-ratio associated with Typhoon Meari-driven
  upwelling 0.29 0.86
• Typhoon Meari might account for 4.1 - 12.0 of
  annual carbon export on the outer shelf of the
  East China Sea

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Summary

• Ocean responses to Typhoon Meari passage
• Upwelling was the main ocean physical response,
• Through upwelling NO3-N was injected to stimulate
  new production,
• Taking into account the factors such as Chl-a
  maximum entrainment, fast regeneration of NO3-N,
  and subsequent NO3-N ventilations, Typhoon Meari
  might account for 4.1 - 12.0 of annual carbon
  export on the outer shelf of the East China Sea.

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Interannual and Interdecadal Variations of
Typhoon Enhanced Primary Production A Case
Study for The Outer Shelf of The East China
Sea Siswanto, E., J. Ishizaka, K. Yokouchi, K.
Tanaka, C.K.Tan Geophic. Res. Let. 34 (2007)
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Background

• The facts have been known
• Typhoon passage can enhance ocean phytoplankton
  chlorophyll-a and primary production,
• The northwest Pacific typhoon activities have
  been known to be related to El Nino/La Nina
  events, but

• Some information have not been understood yet,
  such as
• How El Nino/La Nina events influence ocean
  primary production in the East China Sea through
  typhoon activity,
• Complete interannual and interdecadal variations
  in typhoon-enhanced ocean primary production,
• Estimation of typhoon contribution to summer-fall
  new production in the East China Sea.

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• Study Area
• Area delineated with blue polygonal
• The west border of the area (green contour) is
  0.37 mg m-3 chlorophyll-a (Chl-a) isopleth
  derived from summer mean SeaWiFS Chl-a

• Satellite Data (1998 2004)
• SeaWiFS Chl-a
• SeawiFS photosynthetically available radiation
  (PAR)
• TRMM/TMI sea surface temperature (SST)

• Typhoon Data
• 13 typhoons (red curves and circles) before and
  after which clear SeaWiFS Chl-a data are
  available (from Japan Meteorological Agency)
• Typhoon variables typhoon transit speed (TS) and
  maximum sustained wind (MSW)

• Primary Production Model
• VGPM (Behrenfeld and Falkowski, 1997)

Combined with specific PBopt model for the ECS
(Siswanto et al., 2006)
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Chl-a, PP Enhancements Vs. Typhoon Variables,
Bottom Depth (BD)
PP enhancement
Chl-a enhancement
PP enhancement -28.14 2.57 Mean MSW 0.98
Mean TS 0.04 Mean BD
R2 0.65, p lt 0.001
Empirical relationship
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Extrapolating Empirical Relationship Back to 1980
In general, PP enhancements inversely oscillated
with SOI
PP enhancements were higher during El Nino years
associated with higher MSW
Total PP enhancements were not related to number
of typhoons
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Trend During the Past 25 Years

• Trend Observed
• During the past 25 years, the number of typhoons
  has tended to increase significantly
• (R 0.48, p lt 0.05),
• The mean number of typhoons (gray lines) during
  1991-2004 period (3.9 typhoon yr-1) gt during
  1980-1990 period (2.5 typhoons yr-1),
• As a consequence, mean total PP enhancement
  (black lines) during 1991-2004 period (133 Gg C
  d-1) gt during 1980-1990 period (82 Gg C d-1).

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Summary

• Using typhoon variables and bottom depth, PP
  enhancements due to typhoon passage are possible
  to be estimated even without satellite ocean
  color data,
• Typhoon-enhanced PP was related to El Nino/La
  Nina events as they inversely oscillated with
  ENSO cycle,
• In general, because typhoons tended to be more
  (less) intense during El Nino (La Nina) years,
  typhoon-enhanced PP was also higher (lower)
  during El Nino (La Nina) years,
• Typhoon-enhanced PP has also shown a tendency to
  be higher during 1991-2004 period than that
  during 1980-1990 period,
• Typhoon crossing the ECS might contribute within
  0.4 - 39.7 of the summer-fall new production in
  ECS.

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