Part II: Vriability in the Indonesian Throughflow and Western
Pacific Warm Pool During the Holocene and Common Era.
Yair Rosenthal
Rutgers University
Will briefly summarize (not on Courseworks)
•
Oppo, D.W., Y. Rosenthal, B. K. Linsley; 2000-year-long temperature and hydrology
reconstructions from the Indo-Pacific Warm Pool; Nature, vol. 460, 1113-1116, 2009.
Another related paper from our group to be discussed later by Y. Rosenthal
•
Rosenthal, Y, B. K. Linsley, D. W. Oppo, Pacific Ocean heat content over the past 10,000
years (2013), Science, vol. 342, 617-621, November 1, 2013
Planktonic foraminifera Mg/Ca records of mixed
layer temperatures in the WPWP. (A)
Comparison of Indonesian and WPWP
Globigerinoides ruber Mg/Ca-based surface
temperature anomaly records. Anomalies
calculated as departures relative to average of
last 2,000 years (except for MD41, see table 1).
Bold gray curve is JJA solar insolation at 0°N for
reference. (B) 200 year non-overlapping binned
averages of all 8 cores shown in A (black) and
average of just the 4 southern Makassar region
cores (green). The light green and dashed
bounding lines show the standard error (SE) of
all measurements in each 200 year bin. Dark
gray curves are sea level reconstructions from
Tahiti and Barbados.
Our Preferred Explanation in 2010 was……
: A westward shift or expansion of the WPWP
would explain the early Holocene elevated
SSTs. This would also be in-line with
observations of a more La Niña-like mean
state in the early Holocene.
Mg/Ca – alkenone apparent SST discrepancy
Mg/Ca
alkenone
Mg/Ca – Tex86 SST Makassar
Northern South China Sea SST
Winter SST
Summer SST
Mean annual SST
Shintani et al., 2011
Wei et al., 2007
Model-data comparison
All the models suggest
temperature warming
throughout the Holocene (due
to increase pCO2 and decrease
extent of ice sheets in contrast
with available data
compilations. A seasonal
ecological bias toward summer
months or upwelling periods
can account for some but not
all of this).
Liu et al., 2014 PANS
Possible mechanisms to explain SST changes
in the Indonesian Seaways
1. WPWP SST are influenced
by significant input of
northern Pacific water and
thus exhibit signatures of
northern hemisphere climate
as affected by insolation
Abrupt upper thermocline
cooling beginning 9,500 yr BP
In the Timor Sea downstream
of the ITF.
Xu, J., Holbourn, A., Kuhnt, W., Jian, Z. & Kawamura,
H. Changes in the thermocline structure of the
Indonesian outflow during Terminations I and II.
Earth Planet. Sci. Lett. 273, 152–162 (2008).
Thermocline temperature records along the ITF path
Gibbons et al., in prep.
Makassar
Savu
Makassar
Timor
Gordon 2005
Sunda Shelf flooding
Increase in the atm concentrations of greenhouse gases starting ~6000 years ago
Holocene changes in the mean climate State of the tropical Ocean
Early to late Holocene southward migration of the Atlantic ITCZ, a record from the
Cariaco Basin,Western Tropical Atlantic
( Haug et al., 2001)
A record of Holocene ENSO variability from Laguna Pallcacocha, Ecuador (Moy et al., 2002
Increasing ENSO
frequency or amplitude
AGE
A Holocene Asian monsoon record from the Dongge Cave (southern China)
A southward shift of the ITCZ and weakening of the summer monsoon after ~6
ka, associated with reduced northern hemisphere summer insolation
Su mmer insol ation
65 °N
Wang et al., (2005)
540
530
W/M^2
520
510
500
490
480
inso(W/m2)
470
0
5
10
Age Ka
15
Possible mechanisms to explain SST changes
in the Indonesian Seaways
2. A northward shift of the ITCZ in the early Holocene led to
stronger cross equatorial winds and thus stronger northwestward transport of warm south Pacific tropical water at
the expanse of North Pacific water following Godfrey “Island
Rule”.
Possible implications for ITF:
Early Holocene warmer water and implied higher water
transport.
The southward migration of the ITCZ decreases the cross
equatorial transport
ITF heat transport decreases throughout the Holocene
following Northern Hemisphere insolation.
What about centennial-millennial variability?
Makassar Strait over last 2,000 years: Below shows reconstructed Makassar Strait Sea Surface
Temperature and d18Oseawater (Salinity) vs. Northern Hemisphere Air Temperature
warmer
Medieval Warm
Period
Proxy for
Temperature
cooler
saltier
Proxy for
Salinity
fresher
From Oppo, Rosenthal and Linsley
Nature, vol 460, August 27, 2009
FRESHWATER CONTROLS ON THE INDONESIAN
THROUGHFLOW THERMOCLINE DURING THE LAST
2000 YEARS
Julie Kalansky PhD Thesis 2014
Temperature Proxies:
Sautter 1998
Mg/Ca of N. dutertrei
planktonic foraminifera
Anand et al. 2003;
N. dutertrei calcifies at
80-100 m.
Temp Error ±1.3˚C
~80 m
21
Thermocline temperature and estimated salinity changes
temperature
salinity
MCA
LIA
ITF ENSO response
Ffield et al. 2000
El Nino is associated with cooler temperatures and reduced flow
Susanto et al. 2012
23
Effects of interannual variability of SCS water on the ITF: ENSO connection
• El Nino: more restrictive to the upper ITF
• La Nina: less restrictive to the upper ITF
Gordon et al. (2012)
Strong Luzon throughflow
El Niño
Weak Luzon throughflow
~100 m
Mindanao Current
~100m
Mindanao Current
La Niña
Blocked:
upper ~100m
40 m
40 m
Karimata transport response
to local winds, slightly
stronger in la nina
Mindanao surface layer leakage to ITF
blocked upper ~100 m
Blocked:
upper ~40 m
Mindanao surface layer leakage blocked only in
upper ~40 m
La Niña effect: Warmer ITF reaches into the Indian Ocean, potentially affecting regional sea surface
temperature and climate???
ITF Seasonal Monsoon Response
high precipitation
deep and cool thermocline flow
low precipitation
shallow and warm thermocline flow
25
The 2004 to 2009 Makassar Strait
mean seasonal velocity (filtered).
Maximum southward velocity
occurs in July to September during
the southeast monsoon
The Makassar Strait temperature and
salinity mean seasonal sections
constructed from the January 2004 to
November 2006 INSTANT mooring
measurements (same filter).
Susanto et al. 2012
The Makassar Strait potential
temperature salinity curves
constructed from the January 2004
to November 2006 INSTANT
mooring measurements
EAWM cool/fresh/ min velocity
EASM warm/salty/ mx velocity
Susanto et al. 2012
temperature
salinity
MCA
LIA
28
temperature
precipitation
precipitation
29
Changes in the monsoon system during
the Common Era
Tierney et al., 2010
B. Zhang et al., 2008
C. Tierney et al., 2010
D. Emile-Geay et al., 2013
E. Moy et al., 2002
F. Conroy et al., 2008
G. Steinhilber et al., 2012
31
An intermediate water exchange
through the Makassar – climate
implications
Water Masses passing the Makassar Straits
Hyalinea balthica
Restricted depth / temperature 6-12°C
distribution
High temp-sensitivity
No [∆CO3] ion effect
Easy to clean
~0.64‰ offset from d18O equilibrium
Great candidate for thermocline and
intermediate water reconstructions
(when available)
Rosenthal et al., 2011
16
12
8
4
0
Rosenthal et al., 2013
Comparing Indonesia IWT records with the surface
temperature compilation of Marcott
(Marcott et al., 2013; Rosenthal et al., 2013)
Tidal mixing: can the surface signal reflect mixing with the IWT?
Observatio
n
Control Run
(no tidal
mixing)
With tidal
mixing
Reduce SST by
2oC inside
Indonesia Seas
Reduce
precipitation by
20%
Graphics from Sprintall et al.
(2010), based on results of KochLarrouy et al. (2010)
Changes in OHC
over the past 10,000
years
Implications
to Ocean
Heat Content
Rosenthal et al., 2013
Thoughts
We argue that the heat transport during
the MCA is >0.1 PW higher than in the
LIA. While this heat anomaly is not large
compared with observed interannual
variability, integrated over a few
centuries, it potentially translates into a
large perturbation. Based on this we
would expect greater heat transport
through the Leeuwin Current into the
Indian Ocean thermocline and farther
into the Agulhas Current during the
MCA. This may have been one
mechanism by which the Common Era
climate anomalies were propagated
across the equator into the southern
hemisphere.
Possible global effects: long term anomalies