Large-scale dendrochronology and low-frequency climate variability

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