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LARGE-SCALE DENDROCHRONOLOGY AND LOW-FREQUENCY CLIMATE VARIABILITY
KlimaCampus Colloquium, University of Hamburg | July 9 2015
Sco! St. George University of Minnesota
DECADAL VARIABILITY
Source: Mohino et al., Climate Dynamics, 2011
SAHEL PRECIPITATION ANOMALIES (FILTERED TO EMPHASIZE LOW-FREQUENCY VARIABILITY)
PACIFIC DECADAL
OSCILLATION
1900 1920 1940 1960 1980 2000 2020
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000discharge (cfs) at Grand Forks, North Dakota
Source: United States Geological Survey
THE RED RIVER OF THE NORTH, LEAST STATIONARY RIVER IN THE USA
DECADAL PREDICTION, A NEW FIELD OF STUDY,
FOCUSES ON TIME-EVOLVING REGIONAL CLIMATE CONDITIONS
OVER THE NEXT 10-30 YR, WHICH IS A TIME PERIOD OF INTEREST
TO INFRASTRUCTURE PLANNERS, WATER RESOURCES MANAGERS, AND OTHERS.
“ ”
Meehl et al., 2009 Bulletin of the American Meteorological Society
INSTRUMENTAL CLIMATE OBSERVATIONS
-34°CFORT SNELLING, MINNESOTA
30.1.1820
1900 1920 1940 1960 1980 2000 2020-4
-3
-2
-1
0
1
2
3
4
Source: Dr. Nate Mantua, University of Washington
LOW-FREQUENCY VARIABILITY IN THE NORTH PACIFIC AS REPRESENTED BY THE PACIFIC DECADAL OSCILLATION INDEX
A LIMITATION OF THE INSTRUMENTAL RECORD
IS THAT IT SPANS AT MOST
A FEW REALIZATIONS OF DECADAL VARIABILITY.
“ ”Solomon et al., 2011
Bulletin of the American Meteorological Society
Source: Deser et al., Annual Review of Marine Science, 2010
DISTRIBUTION OF SEA-SURFACE TEMPERATURE OBSERVATIONS FROM THE INTERNATIONAL COMPREHENSIVE
OCEAN ATMOSPHERE DATA SET
Percentage of months with at least one measurement
MODEL SIMULATIONS
Source: Delworth and Zeng, Geophysical Research Le!ers, 2012
INVESTIGATING DECADAL TO MULTICENTENNIAL VARIABILITY OF NORTHERN HEMISPHERE SURFACE AIR TEMPERATURES
IN A 4000-YR CONTROL SIMULATION
IN CCSM4, CENTENNIAL VARIABILITY ARISES PRIMARILY AS A THERMODYNAMIC RESPONSE TO EXPLOSIVE VOLCANISM.
Source: Ault et al., Geophysical Research Le!ers, 2013
… THE USE OF HIGH-RESOLUTION PROXY DATA
SHOULD BE EXPANDED BECAUSE THE SHORT OBSERVATIONAL RECORD
AND MODEL UNCERTAINTY ARE UNABLE TO SIMULATE
[DECADAL CLIMATE VARIABILITY]…
“ ”
Mehta et al., 2011 Bulletin of the American Meteorological Society
Because temperate and boreal forests are so extensive, trees that form annual rings are very common.
Trees routinely a!ain ages in excess of several hundred years.
ADVANTAGES OF TREE-RING WIDTHSAS CLIMATE PROXIES
Source: St. George, Quaternary Science Reviews, 2014
Tree-ring records have annual resolution and the accuracy of their dating is confirmed by a rigorous cross-comparison procedure.
Tree-ring display at elementary school
Photograph: Tom Swetnam
Dr. David Meko University of Arizona
Source: Meko et al., Geophysical Research Le!ers, 2007
MULTI-CENTURY RECONSTRUCTIONS OF COLORADO RIVER FLOW FROM TREE-RING WIDTHS
PROXY ARCHIVES
… PRECIPITATION RECONSTRUCTIONS THAT ARE ENTIRELY BASED ON
TREE-RING WIDTH CHRONOLOGIES MAY CONSIDERABLY OVERESTIMATE
THE TRUE PERSISTENCE OF REGIONAL RAINFALL REGIMES.
“ ”Bunde et al., 2013
Nature Climate Change
THESE LARGE VALUES OF SERIAL CORRELATION SUGGEST THAT THE NON-RANDOMNESS
OF TREE-RING SEQUENCES IS DUE TO THE STORAGE OF FOOD PRODUCTS IN THE TREE
RATHER THAN THE YEAR TO YEAR VARIATIONS OF RAINFALL OR SOIL MOISTURE.
“ ”
Matalas, 1962 International Association of Scientific Hydrology. Bulletin
ADVANTAGE
DISADVANTAGE Short relative to decadal timescales
Firmly grounded in reality
Too sensitive to volcanic forcing?
Simulations are much longer than the timescale of interest
Long records grounded in reality
Proxy systems may distort or exaggerate decadal signals
THE DECADAL CLIMATE “CONUNDRUM”
Dr. Toby Ault Cornell University
1DECVAR ALONG THE CENTRAL PACIFIC COAST
2THE FIDELITY OF PALEO-PDO ESTIMATES
3STRATEGIES TO TRACK PALEO-DECVAR
RINGS IN THE BRANCHES OF SAWED TREES SHOW
THE NUMBER OF YEARS AND, ACCORDING TO THEIR
THICKNESS, THE YEARS WHICH WERE
MORE OR LESS DRY.
“ ”
Leonardo da Vinci
36
EARLYWOOD
LATEWOOD
ONE GROWTH RING
HOW MANY (COMPLETE) TREE RINGS
ARE VISIBLE IN THIS MICROPHOTOGRAPH?
HOW MANY (COMPLETE) TREE RINGS
ARE VISIBLE IN THIS MICROPHOTOGRAPH?
1871 1872 1873 1874
Source: Dr. Dan Griffin, University of Minnesota
Source: Dr. Dan Griffin, University of Minnesota
NORTHWESTERN NEW MEXICO
CRATER LAKE NATIONAL PARK
1809 1811 181218081807
Source: Sarah Appleton, University of Minnesota
IF NO RING WAS FORMED IN A GIVEN YEAR THAT CREATES A FURTHER COMPLICATION
INTRODUCING AN ERROR IN THE CHRONOLOGY ESTABLISHED BY
COUNTING RINGS BACK IN TIME.
“ ”
Dr. Michael Mann Penn State News, February 6. 2012
Source: Esper et al., Dendrochronologia, 2013
If tree-ring records from Europe are shi#ed back one year, their strong correlation with long temperature records disappears.
0% 2% 4% 6% 8%
20°N
40°N
60°N
80°N
Latit
ude
Percentage of locally-absent rings
0% 2% 4% 6% 8%
b
a
Picea Quercus
Pinus Pseudotsuga
Larix Other genera
1500
1000
500
0
# re
cord
s
Source: St. George et al., Geophysical Research Le!ers, 2013
Source: Büntgen et al., Nature Climate Change, 2014
Radiocarbon measurements of a subfossil pine (Pinus cembra) show the same 1.2% increase in 14C from AD 774 to 775.
±0
1DECVAR ALONG THE CENTRAL PACIFIC COAST
Source: Dr. Greg Brooks, Geological Survey of Canada
RED RIVER, CENTRAL CANADA
Source: Flickr user kc7cbf
‘WHITE’total annual precipitation (mm)
ANNUAL PRECIPITATION IN DES MOINES, IOWA
Source: Global Historical Climate Network
Central Pacific Coast
1920 1960 2000
−400
0
400Regional winter precipitation anomalies (mm)
Ault and St. George, Journal of Climate, 2010
CENTRAL PACIFIC COAST
1920 1960 2000
−400
0
400Regional winter precipitation anomalies (mm)
Ault and St. George, Journal of Climate, 2010
CENTRAL PACIFIC COAST
THE HISTORY OF METEOROLOGY IS LITTERED WITH
THE WHITENED BONES OF CLAIMS TO HAVE DEMONSTRATED
THE EXISTENCE OF RELIABLE CYCLES IN THE WEATHER.
“ ”
William James Burroughs Weather Cycles: Real or Imaginary?
Source: California Department of Water Resources
Florsheim, JL, De!inger, MD, 2007. Climate and floods still govern California levee breaks.
Geophysical Research Le!ers.
Source: Ault and St. George, Journal of Climate, 2010
STRONG DECADAL VARIABILITY SYNCHRONIZES RAINFALL, STREAMFLOW, AND HAZARDS IN NORTHERN CALIFORNIA.
A STRONG ATMOSPHERIC RIVERCAN TRANSPORT 7-15X
THE WATER IN THE MISSISSIPPI RIVER
… IN TODAY’S EMBANKED SYSTEM, 81% OF LEVEE BREAKS ALONG CENTRAL VALLEY RIVERS
OCCURRED FLOODS GENERATED BY WINTERTIME [ATMOSPHERIC RIVERS]
WITH ONLY 15% OCCURRING DURING SNOWMELT FLOODS.
“ ”
Florsheim and De!inger, 2015 Geomorphic Approaches to Integrated Floodplain Management
of Lowland Fluvial Systems in North America and Europe,
UNDER THE ‘HASSELMANN’ PARADIGM, THE LOW-FREQUENCY COMPONENTS
ARE DRIVEN BY THE STOCHASTIC HIGHER-FREQUENCY ONES
AND ARE NOT PREDICTABLE.
daysTIMESCALE
VARIANCE
decades
high
low
months
ARE TREE-RING WIDTH RECORDS
ABLE TO TRACK THIS PARTICULAR
NARROWBAND FEATURE?
CRATER LAKE NATIONAL PARK
(a) Winter precipitation
(b) Summer precipitation
(c) Summer temperature
-0.8 +0.8-0.6 -0.4 -0.2 +0.2 +0.4 +0.6
Source: St. George, Quaternary Science Reviews, 2014
WINTER PRECIPITATION
Source: Dr. Dan Griffin, University of Minnesota
QUERCUS DOUGLASII
1700 1750 1800 1850 1900 1950 2000
Tree growth (anomalies)
−0.4
0.4
0
1650
ring-width records
mean of set
Source: St. George and Ault, Journal of Geophysical Research - Atmospheres, 2011
TREE-RING WIDTH RECORDS FROM BLUE OAKS INDICATE THE 20TH CENTURY WAS UNUSUALLY DECADAL.
Source: Dr. Kevin Anchukaitis, University of Arizona
✔
days decadesmonths
UNDER THE ‘BJERKNES’ PARADIGM, THE LONGER TIMESCALES MODULATE THE SHORTER ONES
THROUGH OCEAN PROCESSES AND THEREFORE MAY BE PREDICTABLE.
TIMESCALE
VARIANCE
high
low
Source: NASA
2THE FIDELITY OF PALEO-PDO ESTIMATES
PEYTO LAKE, CANADA
(a) Winter precipitation
(b) Summer precipitation
(c) Summer temperature
-0.8 +0.8-0.6 -0.4 -0.2 +0.2 +0.4 +0.6Source: St. George, Quaternary Science Reviews, 2014
SUMMER TEMPERATURE
Source: Fri!s et al., Journal of Applied Meteorology, 1971
SEASONAL PRESSURE ANOMALIES OVER THE NORTH AMERICAN SECTOR RECONSTRUCTED FROM 49 RING-WIDTH RECORDS
A LONG CLIMATIC RECORD CAN SERVE TO IDENTIFY
THE RANGE OF POSSIBLE CLIMATESAND THE CHARACTERISTICS OF
POSSIBLE CLIMATE “MODES”.
“ ”Fri!s et al., 1971
Journal of Applied Meteorology
(a) El Niño-Southern Oscillation
(b) Pacific Decadal Oscillation
(c) Atlantic Multidecadal Oscillation
-0.8 +0.8-0.6 -0.4 -0.2 +0.2 +0.4 +0.6
Source: St. George, Quaternary Science Reviews, 2014
ENSO
PACIFIC DECADAL
OSCILLATION
PDOD’ARRIGO AND WILSON, 2006
“ON THE ASIAN EXPRESSION OF THE PDO”
D’ARRIGO ET AL., 2001 “TREE-RING ESTIMATES OF
PACIFIC DECADAL CLIMATE VARIABILITY”
BIONDI ET AL., 2001 “NORTH PACIFIC DECADAL CLIMATE VARIABILITY
SINCE 1661”
GEDALOF AND SMITH, 2001 “INTERDECADAL CLIMATE VARIABILITY AND
REGIME-SCALE SHIFTS IN PACIFIC NORTH AMERICA”
MACDONALD AND CASE, 2005 “VARIATIONS IN THE PACIFIC DECADAL OSCILLATION
OF THE PAST MILLENNIUM”
Source: Newman et al,, in revision
… DROUGHTS OCCURRED DURING PERIODS OF BOTH WARM AND COOL KUROSHIO EXTENSION SSTS
AND PERHAPS DURING POSITIVE AND NEGATIVE PDO,
ALTHOUGH THIS IS DEPENDENT ON WHICH PDO RECONSTRUCTION IS USED.
“ ”
McCabe-Glynn et al., 2013 Nature Geoscience
Source: Newman et al,, in revision
POOR REPRODUCIBILITY BETWEEN VARIOUS PDO RECONSTRUCTIONS CALLS TO QUESTION THEIR COLLECTIVE FIDELITY.
Source: Michael Chow
BOULDER, COLORADO
Source: Kipfmueller et al., Geophysical Research Le!ers, 2012
BLACK : WARM PHASE WHITE: COLD PHASE
GREY: NO DATA
ANY CONCLUSION THAT EXTENSIVE WILDFIRES ARE MORE OR LESS COMMON WHEN THE PDO IS IN ONE PHASE OR THE OTHER
DEPENDS ENTIRELY ON THE CHOICE OF PDO RECONSTRUCTION.
WHY HAS IT BEEN SUCH A CHALLENGE
TO RECONSTRUCT THIS ASPECT OF DECADAL VARIABILITY IN THE NORTH PACIFIC?
OCEAN SURFACE HEAT FLUX (VIA THE ALEUTIAN LOW)
OCEAN MEMORY
THE KUROSHIO-OYASHIO CURRENT
+
+
THE PDO =
Source: Newman et al,, in revision
SMALL SETS OF TREE-RING WIDTH
DATA
LARGE-SCALE GEOPHYSICAL PHENOMENA
(a) El Niño-Southern Oscillation
(b) Pacific Decadal Oscillation
(c) Atlantic Multidecadal Oscillation
-0.8 +0.8-0.6 -0.4 -0.2 +0.2 +0.4 +0.6
Source: St. George, Quaternary Science Reviews, 2014
PDO
PinusPicea
QuercusPseudotsuga
Larix
NothofagusAustrocedrisPhyllocladus
Agathis
Source: St. George, PAGES Magazine, 2014
There are more than 3,200 publicly-available tree-ring records (and many more held by individual investigators).
3STRATEGIES TO TRACK PALEO-DECVAR
Source: Gray et al., Geophysical Research Le!ers, 2003
Most dendroclimatic studies first reconstruct an annually-resolved target variable, and then apply some form of filter to emphasize decadal behavior.
IMPROVING ESTIMATES OF INTERMEDIATE-SCALE
VARIABILITY
TREE-RING WIDTHS BECOME SMALLER AS THE TREE GETS OLDER
BECAUSE OF THE GEOMETRICAL CONSTRAINT CREATED BY ADDING A VOLUME OF WOOD
TO A STEM OF INCREASING RADIUS.
[AGE-SIZE TRENDS IN TREE-RING WIDTH] SHOULD BE THOUGHT OF AS
A NONSTATIONARY, STOCHASTIC PROCESS THAT MAY, AS A SPECIAL CASE,
BE MODELED AS A DETERMINISTIC PROCESS.
“ ”Cook and Briffa, 1990
Methods of Dendrochronology
(A) the ‘raw’ ring-width data
(B) the ‘detrended’ ring-width
index
THE MOST OBVIOUS SOURCE OF NONCLIMATIC PERSISTENCE
IN TREE-RING DATAIS ERROR IN REMOVAL OF
THE GROWTH TREND WHEN CONVERTING ANNUAL RING WIDTHS
TO TREE-RING INDICES.
“ ”
Meko, 1981 Doctoral dissertation, University of Arizona
PRESERVING DECADAL VARIANCE IN DENDROCLIMATIC RECONSTRUCTIONS
Dr. Toby Ault Cornell University
CHRONOLOGY RECONSTRUCTIONmean-value function
representing annual tree growth across many dozens or hundreds of trees
quantitative estimate of a climate variable
derived from one or several tree-ring chronologies
Source: Adapted from Ault et al., Journal of Climate, 2013
PALEO-PRECIPITATION RECONSTRUCTIONS FROM TREE RINGS HAVE LESS VARIANCE AT LOW FREQUENCIES
THAN THE ORIGINAL TREE-RING CHRONOLOGIES.
Chronology ‘A’
Chronology ‘B’
Chronology ‘C’
Chronology ‘D’
Chronology ‘E’
Chronology ‘F’
Chronology ‘G’
Chronology ‘H’
Chronology ‘I’
Chronology ‘J’
Reconstruction10 predictors76421
THE NESTED RECONSTRUCTION APPROACH GENERATES A NEW MODEL FOR EACH SUBSET OF PREDICTORS.
Source: Cook et al., Journal of Quaternary Sciences, 2010
THE NORTH AMERICAN DROUGHT ATLAS USES A NETWORK OF MOISTURE-SENSITIVE TREE-RING RECORDS TO ESTIMATE CHANGES IN DROUGHT CONDITIONS
ACROSS THE CONTINENT.
450 km
A FIXED SEARCH RADIUS AROUND EACH GRID POINT DEFINES THE ZONE OF LOCAL CONTROL
EXERCISED BY THE METHOD IN SELECTING CANDIDATE TREE-RING PREDICTORS
OF PDSI.
Source: Cook et al., Journal of Climate, 1999
CHOOSING ALTERNATIVE DECADAL TARGETS
FOR RECONSTRUCTION
OCEAN SURFACE HEAT FLUX (VIA THE ALEUTIAN LOW)
OCEAN MEMORY
THE KUROSHIO-OYASHIO CURRENT
+
+
THE PDO =
Source: Newman et al,, in revision
IF THE RELATIVE IMPORTANCE OF THESE CONTRIBUTIONS VARIES,
THEN THE APPARENT TELECONNECTION FROM THEIR SUM (THE PDO) COULD BE
NONSTATIONARY EVEN IF TELECONNECTIONS
TO THE INDIVIDUAL PDO PROCESSES WERE FIXED.
“ ”
Newman et al., in revision Bulletin of the American Meteorological Society
Source: Zanche!in et al., Climate of the Past, 2015
PACIFIC/ NORTH AMERICAN
PATTERN
THESE RESULTS CALL FOR STRENGTHENED COOPERATION BETWEEN THE CLIMATE PROXY
AND CLIMATE MODELING COMMUNITIES IN ORDER TO IMPROVE OUR KNOWLEDGE ABOUT THE EARLY 19TH-CENTURY PNA
AND TO SOLVE THE RELATED RECONSTRUCTION-SIMULATED DISCREPANCY.
“ ”
Zanche!in et al., 2015 Climate of the Past
Dr. David Meko University of Arizona
Source: Meko, Ph.D. dissertation, 1981
TREE-RING RECORDS ARE ABLE TO TRACK DECADAL CLIMATE VARIABILITY, AT LEAST IN SOME CASES.
BUT WE NEED TO SPECIFICALLY TEST THEIR FIDELITY AT THOSE TIMESCALES.
TREE-RING ESTIMATES OF DECADAL CLIMATE MODES ARE NOT CONSISTENT PRIOR TO THE 20TH CENTURY.
THAT LACK OF AGREEMENT COULD TELL US SOMETHING ABOUT THE STABILITY OF TELECONNECTIONS
ASSOCIATED WITH DECADAL MODES.
ACCURATELY EXTRACTING DECADAL SIGNALS FROM TREE-RING PROXIES IS A LONGSTANDING PROBLEM.
THE PALEO-COMMUNITY MIGHT NEED TO ADOPT (AND TEST) NEW STRATEGIES TO DEAL WITH
OUR PARTICULAR DECADAL ‘CONUNDRUM’.
SCOTT ST. GEORGE DEPARTMENT OF GEOGRAPHY, ENVIRONMENT AND SOCIETY
UNIVERSITY OF MINNESOTA
@SCOTTSTGEORGE