Holocene droughts, fires, floods and pluvials in southwestern California.
• Matthew Kirby• Professor, Cal-State Fullerton
• Dept. of Geological Science
• SCEC SoSAFE Workshop: Recent Successes and Future Challenges (Sept. 10, 2016)
• 13:30-14:00
STUDENTS.Special Thanks to:Christine Hiner, Joanna Fantozzi, Brittany Pyke, Pedro Monarrez, Bradley Markle, Shauna Nielsen, Lauren Rivera-Mirallegro, Luissa Ivanovici, Jenn Schmidt, Joe Carrasco, Michael Blazevic, Jose Rivera, Broxton W. Bird, Emily Silveira, Alex Woodward
FUNDING.Special Thanks to:National Science Foundation, American Chemical Society-Petroleum Research Fund, CSUF, Sigma Xi, Geological Society of America, Big Bear Municipal Water Authority, Lake Elsinore-San Jacinto Water Authority
Acknowledgements
COLLABORATORS.Special Thanks to:Sarah Feakins, Bill Patterson, Steve Lund, Susan Zimmerman, Michael Anderson, Scott Starratt, Glen MacDonald, Chris Scholz
Talk Organization
1. What is Paleoclimatology? And, How do we reconstruct past climate?
2. Holocene Climates in the coastal SW US
3. Relevance to Paleoseismology 4. Future Opportunities?
What is paleoclimatology?• paleoclimatology is the study of past
climate
Zaca Lake mud
How do we investigate past climate?• we use proxies contained in geological
archives to reconstruct past climate• geological archives include...
• ice cores• marine sediments• lake sediments• tree rings• cave deposits• coral
• a proxy is a substitute for a climate or climate related variable such as...• temperature• precipitation• atmospheric circulation patterns• ocean circulation patterns• flood events• fire activity• vegetation• geomorphic disturbance
Zaca Lake, CA (July 2009)
How do we investigate past climate?• I use proxies preserved in the sediment at the bottom of lakes/
wetlands (which, by the way, are rare in So Cal!) or any basin, really.• Sediments contain a combination of...
• weathered and eroded materials such as rock and soil...• materials produced within the lake such as phytoplankton
or chemically precipitated minerals (e.g., calcium carbonate)
• eolian materials such as dust, pollen, leaf waxes
Core LEGC03-4
flame structuresflame structures
erosional basal contactfingerprint
laminae
gradationalupper contact
Depth (cm)
330
329
317
318
319
320
321
322
323
324
325
326
327
328
Figure 5
Holocene Climates in the coastal SW US• Remarkably, our knowledge of past climate in the coastal
southwest US was extremely limited, until recently…• limited to some tree ring records (<1000 yrs), low
resolution sediment records, and packrat middens (Lynch 1931; Wells and Berger 1967; Ore and Warren 1971; Heusser 1978; Meko et al. 1980; Cole and Webb 1985; Enzel et al. 1989, 1992; Spaulding 1990; Rosen 1991; Brown and Rosen 1995; Cole and Wahl 2000; Biondi et al. 2001; D’Arrigo et al. 2001; Byrne et al. 2003)• note: I am not including the SBB records in this
talk• Relevant to this workshop are…
• Sediments that accumulate in basins - lakes, wetlands, sag ponds(?), etc…• often continuous• can capture annual to millennial scale
information• record geomorphic processes• are not limited to past 1000-2000 yrs, as are tree
rings• tree rings are extremely important archives
BUT they cannot tell us about • past floods, • geomorphic responses to climate such
as drought, • fire activity, • vegetation changes, • and many other things that are stored in
basin sediments…• And, they are also poorly represented in arid
environments like the coastal SW US• so, we need other sources of paleoclimatic information!
Kirby et al. in review Lake Elsinore mega flood event
4.8kyrs BP
Holocene Climates in the coastal SW US• Developed paleoclimate sites
• as relevant to this workshop and their value to the paleoseismic record
no tree rings no packrat middens
Lots of unknowns!
with tree rings no packrat middens
Still lots of unknowns!
• So, let’s take a virtual tour through time…
WARNING!!*lots of wiggles ahead
*lots of quick explanations
Holocene Climates in the coastal SW US
• Holocene perspective• Millennial scale
• Milankovitch (insolation) and large-scale Pacific ocean-atmosphere dynamics drive the signal
• Examples• Lake Elsinore (Kirby et al. 2004, 2005, 2007, 2010, 2013; Heusser et
al. 2015)• Dry Lake (Bird and Kirby, 2006; Bird et al., 2010)• Silver Lake (Kirby et al., 2015)
Holocene Climates in the coastal SW US
Silver Lake (Kirby et al. 2015)
3
2
1
0
-1
-2
1000 5000 9000 13000
Stn
dzd
percen
t cla
y
relative
lake
status
perennial
ephemeral
YD LM
II
BAEarly Holocene
Pluvial
Mid Holocene
Arid Interval
Late Holocene
EL
Age, cal yr BP
30
20
10
0-1
0
112
10
8
3
2
1
0
-1
-2
10
8
6
4
2
0
0
-2
-4
-6
-8
-101000 5000 9000 13000
Percent Sand
MoreEl Niños
LessEl Niños
SST (°C)
W -
E Pa
cific
SST
grad
ient
ano
mal
y (°
C)Weaker
gradient
Strongergradient
Perc
ent d
iff. s
umm
er/
win
ter i
nsol
atio
n fr
omm
oder
n at
30°
N
Stnd
zd p
erce
nt c
lay
relativelakestatus
perennial
ephemeral
YD LMII
BAEarly HolocenePluvial
Mid HoloceneArid Interval
Late HoloceneEL
ODP Site 1019(Barron etal., 2003)
Tropical Pacific(Koutavas andJoanides, 2012)
El Junco(Conroy etal. 2008)
(Las
kar e
t al.,
199
3)
Calendar Years Before Present
• Holocene perspective• Sub millennial to centennial scale
• Pacific sourced ocean-atmosphere forcing (ENSO, PDO) - evidence for climate state changes?• Holocene pluvials
• Examples• Lake Elsinore• PDO forcing
• Lower Bear Lake• Holocene pluvials• linked to changes in atmospheric river
frequency?
Holocene Climates in the coastal SW US
Lake Elsinore (Kirby et al. 2010)
Lower Bear Lake (Kirby et al. 2012)
• Holocene perspective• Sub Centennial to decadal scale
• Pacific sourced ocean-atmosphere forcing (ENSO, PDO)• data indicate real spatiotemporal variability• requires improved and quantitative wiggle matching• working with 2 CSUF statistics professors (Drs. Kevin
Nichols and Reza Ramezan) to quantify the patterns of climate change across different records with varying age control
• extending this comparison to aggregate tree ring records for the region• Examples• Zaca Lake• tropical Pacific forcing
• Abbott Lake (Kirby et al. in press)• tropical and N Pacific forcing
• Crystal Lake• a storm story linked to tropical and N Pacific forcing
Holocene Climates in the coastal SW US
Zaca Lake (Kirby et al. 2014; Feakins et al. 2014; Dingemans et al. 2014)
more run-off/wetter
less run-off/drier 9-
pt. s
moo
th p
erce
nt12
5 to
200
0μm
*regime shift detection from Rodionov, 2004 cy BP
Calendar Years BP0 1000 2000 3000
9-pt
. sm
ooth
per
cent
>125
to 2
000μm
0
2
4
6
A.
B.
More run-off/wetter
Less run-off/drier
200
400
600
μg/g
OC Dinosterol
(El Niño)
Cholesterol(La Niña)
C.
More intenseEl Niños/La Niñas
Fewer intenseEl Niños/La Niñas
LHDP(Mensing et al., 2013)IPCC LIA
IPCCMCA
Figure 9
F F F F F F F end of record
More El Niños
Fewer El Niños
Perc
ent S
and
0
10
20
30
Zaca Lake (Kirby et al. 2014)
Conroy et al., 2008
Makou et al., 2010
SBB flood events
• Holocene perspective• Annual scale
• generally a Pacific sourced ocean-atmosphere forcing…other things too (e.g. volcanism)• Examples
• Cook et al. (2004, 2009) PDSI reconstructions• how do these records relate to sediment based
reconstructions? Zaca vs. Tree Rings
Holocene Climates in the coastal SW US
Cook et al. (2004) Epic Droughts
data from Cook et al. (2004)
Zaca
>12
5 µm
sand
(9pt
. sm
ooth
)C
SWU
S PD
SI
Calendar Years Before Present
Dro
ught
Are
a w
este
rn U
S
IPCCLIA
IPCCMCA
DDD
D
WWWW 20
40
60
data from Cook et al. (2004)
way more epic
Relevance to Paleoseismology• “While several studies have compared paleoseismic event histories at neighboring sites to appraise
earthquake synchronicity (e.g., Onderdonk et al. 2013; Scharer et al. 2014), there have yet to be comprehensive studies that focus on the climatically-controlled geomorphic changes throughout the earthquake record. For instance, are there simultaneous depositional or erosional events across regions of southern California that we can tie to an historical mega-flood or decade-long wet period? If yes, as proposed by Grant-Ludwig et al. (2010) and Scharer et al. (2014), we can use sedimentary and pedogenic records of these geomorphic events as benchmarks to refine the paleoseismic record.” quoted directly from proposal by Salisbury and Arrowsmith (SCEC prop 2015)
Relevance to Paleoseismology• Clearly, paleoseismic sites
contain a wealth of paleoclimatic data…but, only if approached with the correct methodologies/protocols• sampling• dating• recovery time for climate
signal to establish post-disturbance
• coring will not work (see next slide)
Relevance to Paleoseismology• Example of issues…
Wow, what a beautiful section! -core #1
Hmmm, what an ok section.
-core #2
D’oh! what a crappy section! -core #3
*oh no! cores at this site would equal paleoclimatic failure!! *what’s the solution for working in seismically disturbed basins (e.g. sag ponds…) -paleoclimatologist and paleoseismologist must work together in the open trench to deconvolve the climatic and seismic history!
Future Opportunities?• Remember the slide with the tree and sediment sites?
• mostly empty• BUT, a lot of that emptiness can be filled using
paleoseismic sites where permanent lakes and trees are rare• climate is spatially and temporally complex…
• we MUST fill in the spatial and temporal gaps IF climate records are to be used as “benchmarks to refine the paleoseismic record”
• but, sediment-based paleoclimate work requires $$• So, where do these future collaborations find their
funding?
Thank You!10/0.5
20/8.0
30/15.5
40/23
50/30.5
60/38
70/45.5
80/53
90/60.5
100/68
110/75.5
TWTT
(ms)
/met
ers b
elow
lake
bot
tom
LE line 10
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900Distance (m)
seismic reflection line down the long axis of Lake Elsinore, CA (Kirby et al. in prep)