This document summarizes an ongoing study examining changes in precipitation and seawater isotopes across sites in the Pacific during the major 2014-2015 El Niño event. Key findings so far include anomalous warming of over 4°C at Christmas Island, doubling of rainfall rates there with isotopically lighter rain consistent with the amount effect, and a decrease in seawater oxygen-18 of around 0.3‰ at Christmas Island. The authors aim to better understand spatial and temporal variability in water isotopes to improve paleoclimate proxy interpretations and validate isotope-enabled climate models using this natural ENSO experiment.

1. Precipitation and seawater isotopes from
Hawaii to the equator across the 2014-2015
ENSO cycle
Kim M. Cobb (Georgia Tech)
@coralsncaves
Jessica L. Conroy (U. Illinois Urbana-Champaign)
Christopher Bosma, Lucas Everitt, Pamela Grothe
(Georgia Inst. of Technology)
Jessica Moerman (Johns Hopkins)
Julia Baum (U. Victoria)
David Noone (Oregon State University)
Samantha Stevenson, Mark Farnsworth (NOAA)
Brian Powell, Mark Merrifield, Niklas Schneider (U. Hawaii-Manoa)
OK

3. Coral d18O reconstructions
of climate require an
understanding of
seawater d18O variations
World Ocean Atlas, 2009
(E-P) ocean
circulation
seawater d18O
(salinity?)
climate
Coral d18O = SST + d18Osw
d18Ovapor
d18Orain

4. To unlock the full potential of paleo-isotope records,
we need to know:
1) How does d18O of seawater vary through space and time?
(and relationship to salinity?)
2) What are the relative contributions of ocean circulation
versus atmospheric fluxes to d18Osw variability
at a given site?
3) What are the local vs. regional drivers of rainfall
d18O variability at a given site?

5. To unlock the full potential of paleo-isotope records,
we need to know:
1) How does d18O of seawater vary through space and time?
(and relationship to salinity?)
2) What are the relative contributions of ocean circulation
versus atmospheric fluxes to d18Osw variability
at a given site?
3) What are the local vs. regional drivers of rainfall
d18O variability at a given site?
Applications: improve paleo-proxy interpretations
validation/assimilation data for isotope-
equipped models

6. Borneo
Cobb lab daily rainwater collections began in 2005 in Borneo
Map of past
and/or present
GNIP rainfall
collection sites;
plotted on rainfall δ18O
source here

7. Oahu
Christmas
Palmyra
Galapagos
Ecuador
Palau
PNG
Borneo
Cobb/Conroy lab water isotope collection sites
daily rainwaters since 2005, weekly seawaters since 2012
Map of past
and/or present
GNIP rainfall
collection sites;
plotted on rainfall δ18O
source here

8. http://www.esrl.noaa.gov/psd/map/clim/sst.shtml
The right place at the right time . . .

9. http://www.esrl.noaa.gov/psd/map/clim/olr.shtml

10. Aspects of the water isotope budget that change
across a major El Niño event:

11. Aspects of the water isotope budget that change
across a major El Niño event:
EVERYTHING

12. Aspects of the water isotope budget that change
across a major El Niño event:
EVERYTHING
Focus on rainfall, seawater d18O obs today . . .
But see
PP41D-06 Identifying Oxygen Isotopic Signatures of ENSO
Dynamics Through Isotope-Enabled Regional Ocean Modeling
S. Stevenson et al., Thursday 9:15am MW 2010

13. Ongoingefforts:dataassimilation,field obs during2014-16Christmas coral d18O vs. iso-ROMS coral d18O
Stevenson et al.,
Paleo. 2015
coral

14. Ongoingefforts:dataassimilation,field obs during2014-16Christmas coral d18O vs. iso-ROMS coral d18O
Stevenson et al.,
Paleo. 2015
coral
GOAL:
iso-hindcast of 2014-2016 ENSO cycle

15. 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016
24
26
28
30
Year
SST(
o
C)
TOGA/TAO 2N 155W SST
2015: A record-breaking El Niño
in central tropical Pacific

16. 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016
24
26
28
30
Year
SST(
o
C)
TOGA/TAO 2N 155W SST
2015: A record-breaking El Niño
in central tropical Pacific
Fieldwork
Nov 2015
Nov 1997

17. 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016
24
26
28
30
Year
SST(
o
C)
Seabird loggers w/ TOGA/TAO 2N 155W SST
loggers track open-ocean temperatures
water temperatures > 31°C measured
last month at Christmas Island

18. 2012 2014 2016
24
25
26
27
28
29
30
31
Year
SST(
o
C)
Seabird loggers w/ TOGA/TAO 2N 155W SST
TOGA/TAO
SouthShore
Leeward
Windward
leeward and windward side quite similar,
at least during El Niño event

19. 01/13 01/14 01/15 01/16
0
20
40
60
80
100
120
Year
Christmas Rainfall Amount (mm/day)
d18O(‰) Christmas Rainfall d18ORainfall(mm/day)
Christmas Rainfall Amount
-4.2‰
-2.1‰
22
10

20. 01/13 01/14 01/15 01/16
0
20
40
60
80
100
120
Year
Christmas Rainfall Amount (mm/day)
d18O(‰) Christmas Rainfall d18ORainfall(mm/day)
Christmas Rainfall Amount
-4.2‰
2.1‰
22
10
Getting more rain, and lighter rain,
during El Niño event
 impact on seawater isotope budget?

21. dD=5.8d18O+7.7
dD=7.0d18O+6.5
dD=8.1d18O+13.3
dD=7.7d18O+13.0
2014
2015
Christmas Rainfall LMWLs
d18O (‰)
dD(‰)
LMWL slope goes from
~5 during normal
conditions to ~8
during El Niño event

22. dD=5.8d18O+7.7
dD=7.0d18O+6.5
dD=8.1d18O+13.3
dD=7.7d18O+13.0
2014
2015
Christmas Rainfall LMWLs
d18O (‰)
dD(‰)
LMWL slope goes from
~5 during normal
conditions to ~8
during El Niño event
d-excess goes from
10‰ to 15‰ going
into El Niño event

23. 2013 2014 2015 2016
0
0.2
0.4
0.6
Year
Christmas Seawater isotopes
2013 2014 2015 2016
33
33.5
34
34.5
35
35.5
36
Year
Christmas Salinity
d18Osw(‰) Christmas Seawater d18OSalinity(psu)
Christmas Salinity
0.2‰
0.48‰
34.4
34.6‰

24. 2013 2014 2015 2016
0
0.2
0.4
0.6
Year
Christmas Seawater isotopes
2013 2014 2015 2016
33
33.5
34
34.5
35
35.5
36
Year
Christmas Salinity
d18Osw(‰) Christmas Seawater d18OSalinity(psu)
Christmas Salinity
0.2‰
0.48‰
34.4
34.6‰
>0.3‰ decrease in d18Osw
will have major effect on coral d18O

25. d18O(‰)
Christmas SSS vs seawater d18Osw
Salinity (psu)
d18Osw– SSS
relationship
poorly constrained,
but little change
outside El Niño
event

26. d18O(‰)
Christmas SSS vs seawater d18Osw
Salinity (psu)
d18Osw– SSS
relationship
poorly constrained,
but little change
outside El Niño
event
we will add 4x
more data by
end of 2016,
spanning
strong La Niña
event

27. Oahu
Christmas
Palmyra
Galapagos
Ecuador
Palau
PNG
Borneo
A pan-Pacific iso-view of a strong ENSO extreme
Map of past
and/or present
GNIP rainfall
collection sites;
plotted on rainfall δ18O
source here

28. Conclusions
The 2015/2016 El Niño event has already led to:
anomalous warming of ~4°C on Christmas reef
doubling of rainfall rates, and ~2‰ decrease
in d18OR, consistent with amount effect
~0.3‰ decrease in d18OSW
expect coral d18O decrease of >1‰

29. Opportunities for capacity-building
TPOS2020: isotope-equipped?
or at least iso-friendly by design? (urgent)
We need a new archive for water isotope data.
- interest in community workshop?
Fate of long-term isotopic timeseries?

30. THANKS
THANKS