NOTE

New evidence for extreme and persistent terminal medievaldrought in California’s Sierra Nevada

Christopher Morgan • Monique M. Pomerleau

Received: 4 June 2011 / Accepted: 20 February 2012 / Published online: 17 March 2012

� Springer Science+Business Media B.V. 2012

Abstract The level of Cliff Lake, a small, subalpine,

moraine-dammed lake in California’s south central

Sierra Nevada, was approximately 5 m lower than

present for 50 years or more approximately 600 years

ago, this determined by radiocarbon dating of wood

recovered from a submerged tree stump found in the

lake. This finding corresponds to commensurate data

from throughout much of western North America,

suggesting the duration and magnitude of terminal

medieval megadrought was similar throughout the

region. Ultimately this datum helps give credence to

the perspective that though late Holocene climate in

California was indeed variable, the effects of terminal

Medieval megadrought was similar across both time

and broad geographic expanse.

Keywords Medieval climatic anomaly � Sierra

Nevada � Drought � Precipitation � California � Lake �Submerged stump � Climate change � Megadrought

Introduction

Recently, Kotlia et al. (2011) argued that lake records

offer one of the best ways of understanding the extent

and magnitude of shifts in Holocene moisture

regimes and that identifying consistency in the

effects of the Medieval Climatic Anomaly (MCA:

1,650–650 cal year BP) across broad geographic

regions was one of six main research goals for those

interested in climate’s effects on environmental

resources and societal development. This is impor-

tant because even though there is presently abundant

evidence for a general pattern of elevated tempera-

tures and reduced precipitation during this time in the

northern, and perhaps southern hemisphere (Bradley

et al. 2003; Cook et al. 2004, 2010; Jones et al. 1998;

Mayewski et al. 2004; Rein et al. 2004), others note

temporal and geographic variability in the magnitude

of medieval aridity (Briffa et al. 2001; Hughes and

Diaz 1994). Because the ecological effects of climate

change are determined primarily by water budgets, or

by what Stine (2000) calls the ‘‘hydroscape’’, multi-

ple and accurate water budget proxies are essential to

reconstructing the geographic extent and effects of

past climatic variability (Bradley et al. 2001; Graham

and Hughes 2007; Mann 2002), particularly in a

region as large and geographically diverse as Cali-

fornia. Submerged stump studies such as the one

reported here consequently provide direct evi-

dence for climatically-induced lake desiccation com-

plementary to more traditional paleoenvironmental

C. Morgan (&)

Department of Anthropology, University of Nevada,

Reno, 1664 N. Virginia Street, Reno, NV 89557-2226,

USA

e-mail: christophermorgan@unr.edu

M. M. Pomerleau

381 W 100 N, Logan, UT 84321, USA

e-mail: mopomerleau@gmail.com

123

J Paleolimnol (2012) 47:707–713

DOI 10.1007/s10933-012-9590-9

proxies like pollen cores, sedimentological analysis

and tree rings.

Within this context, this brief paper presents

geomorphic and radiometric evidence for significant

changes in the level of Cliff Lake, a subalpine lake on

the west slope of California’s Sierra Nevada (Fig. 1).

It documents a 5-m decrease in lake levels approxi-

mately 600 years ago. The timing of this lowstand

corresponds to similar research identifying contem-

poraneous recessions to the north and east, and to more

general regional drought sequences derived from

palynological, dendroclimatological and other proxy

data sets. These findings help map the geographic

extent and intensity of medieval droughts in the

region, ultimately supporting the argument that the

magnitude of terminal medieval drought was similar

across much of California, western Nevada and

southern Oregon. These findings corroborate those

identifying megadroughts (droughts whose duration

exceed those of the instrument record) across most of

the American West ca. AD 1,250–1,300 (Cook et al.

2004, 2010; Herweijer et al. 2007) and refutes

competing perspectives that see substantial variability

in the local effects of medieval warming (Basgall

1999) and considerable differences in past regional

precipitation regimes (Haston and Michaelson 1997).

The source of this new data point, Cliff Lake, is in a

glacially scoured granitic basin in the Dinkey Lakes

Wilderness, Sierra National Forest (37�08.550N;

119�02.780W), at 2,831 m elevation (Fig. 2). The lake

is 530 m long and 280 m wide at its widest point, with

a surface area of approximately 1.2 km2. Its maximum

depth is unknown, but most of the lake bottom is

visible from the lake surface and appears no more than

about 8 m deep. The lake spills from a terminal Tioga-

age (ca. 15 ka) moraine at its southeastern end into

Nelson Creek, a minor perennial stream in the

northern Kings River watershed. Tioga-age moraines

at this elevation and the basins they enclose have been

in-place, stable and have not been significantly

affected by tectonic activity since before the close of

the Pleistocene (Birman 1964; Curry 1969). A large

granite dome abuts the northwest end of the lake (the

‘‘cliff’’ for which the lake is named), below which is a

small beach of Holocene sands. The south side of the

lake is ringed by Quaternary alluvium on which

shallow, modern forest soils have developed. Granite

bedrock rings much of the north shore of the lake. No

streams feed the lake; rather, it catches runoff from a

small, roughly 6 km2 watershed blanketed by large

exposures of granite bedrock and excessively drained

soils derived from underlying bedrock and glacial till

(USDA 1993). Vegetation is patchy and dominated by

Pinus contorta Douglas ex Loudon, with an under-

story of woody shrubs (e.g., Ceanothus cordulatus

Kellogg) and herbaceous perennials (e.g., Eriogonum

nudum Benth.).

Methods and results

The bottom of Cliff Lake was visually inspected by

swimming parallel, 10–20 m wide surface transects

around its perimeter. When deadfall or stumps were

identified, they were dove to and closely inspected to

determine whether they were embedded in lake

sediments and whether they appeared to have grown

Cliff Lake

California

Oregon

NevadaSierra

Nevad

a

34

6

7

9

108

1

2

511

Fig. 1 Location of studies mentioned in the text: (1) Diamond

pond; (2) Pyramid lake; (3) Lake Tahoe and Independence lake;

(4) Fallen leaf lake and Osgood swamp; (5) West walker river

(6) Walker lake; (7) Mono lake; (8) White Mts; (9) Sacramento

river; (10) East lake; (11) Sacramento-San-Joaquin Delta.

Shaded numbers indicate locations with submerged terminal

medieval stumps

708 J Paleolimnol (2012) 47:707–713

123

in place (i.e., perpendicularly embedded in lake

sediments, with an intact root ball at its base, and

with little or no evidence of disturbance to the lake

bottom). One stump in the northwestern portion of the

lake meets these criteria. It was found submerged 5 m

below the lake surface, protruding from loose, sandy

lake sediments (Fig. 3). The stump is P. contorta,

measures 0.6 m in diameter and extends some 1.5 m

above the lake bottom. A sample was removed from

the outside rind of the stump with a small handsaw

in order to identify an approximate date of death for

the tree. The sample was pretreated using the acid-

alkali-acid method (Hajda 2006) and analyzed using

standard radiometric techniques (i.e., by synthesizing

the sample carbon to benzene [92% C], measuring the14C content in a scintillation spectrometer, and

calculating the radiocarbon age from measured

results). The measured 14C age of the sample (Beta

209200) is 550 ± 50 14C year BP, calibrated at 2

sigma to 660–530 cal year BP (AD 1290-1420) with

INTCAL04 (Reimer et al. 2004; Talma and Vogel

1993). This date indicates water budgets were reduced

to such an extent as to keep Cliff Lake maximum pool

elevation 5 m or more lower than modern lake levels

for a period of time long enough to grow a large

conifer (P. contorta) with a diameter of at least 0.6 m.

Cliff Lake

Bullfrog Lake

MoraineDam

NelsonCreek

0 100 500 m Contour Interval 12 m

SampleLocation

North

(2831 m)A

pproximate

Watershed

Boundary

Fig. 2 Study area showing

watershed and sample

location

J Paleolimnol (2012) 47:707–713 709

123

Such a span is likely on the order or 50 years or more

(Lanner 1984), suggesting prolonged and pronounced

drought in the Cliff Lake watershed prior to roughly

595 cal year BP (AD 1355), the mean date associ-

ated with the death of the tree, ostensibly by lake

transgression.

Discussion

The data point from Cliff Lake indicates that terminal

medieval drought affected the south-central Sierra

Nevada severely enough so as to substantially restrict

water budgets for 50 years or more, qualifying it as a

megadrought (Woodhouse and Overpeck 1998; Stahle

et al. 2007) terminating ca. 595 cal year BP. This date

corresponds most immediately to Stine’s (1994)

terminal medieval drought, identified by what he calls

‘‘G-2 Stumps’’ in Mono Lake, Walker Lake and the

West Walker River, each documenting drought ter-

mination (tree death date by inundation) between 600

and 550 cal year BP (see Fig. 1 for all subsequent

study area locations). These findings roughly corre-

spond to the Mono Lake water budget models of

Graham and Hughes (2007), who identify drought

774–676 cal year BP (AD 1176–1274). Similar

stumps have been found and dated ca. 4 m beneath

the surface of Lake Tahoe and nearby, at Indepen-

dence Lake (Lindstrom 1990). The former date to the

mid-Holocene (ca. 5,000 cal year BP); the latter (at

ca. 630 ± 50 cal year BP) correspond to the date from

Cliff Lake and Stine’s G-2 Stumps. Similarly, at

Fallen Leaf Lake, Biondi et al. (2006a, b) uses

dendrochronology to date stumps 20 m below the

lake’s surface to ca. 800 cal year BP. These dates

correspond to Stine’s (1994) earlier medieval ‘‘G-1

Stumps’’ (from the aforementioned three locations as

well as from Osgood Swamp, just south of Lake

Tahoe). Importantly, all of these studies found

submerged stumps in the Sierra Nevada rain shadow,

on the eastern side of the range. The stump at Cliff

Lake is the first to document similar and contempo-

raneous desiccations on the more mesic western slope

of the range, in a source watershed for one of the Sierra

Nevada’s principal westward-flowing rivers, the

Kings.

These findings correspond to multiple regional

climatic proxies. The paleoclimatic and paleoenviron-

mental literature of the Sierra Nevada and surrounding

region is considerable and reviewed elsewhere (Spaul-

ding 1999; West et al. 2007; Woolfenden 1996) but

several studies stand out. First, treeline elevation

studies in the White Mountains immediately east of

the Sierra (LaMarche 1973) and in the central and

southern Sierra Nevada itself (Lloyd and Graumlich

1997; Scuderi 1987b), show treelines increasing in

elevation, ostensibly due to increased temperature,

between about 950 and 550 cal year BP, a pattern

corresponding to White Mountain bristlecone pine

dendrochronologies (Hughes and Graumlich 1996).

These findings correspond to evidence from the

central Sierra Nevada for temperature and precipita-

tion-mediated increases in fire frequency between 950

and 650 cal year BP (Anderson and Smith 1997;

Swetnam 1993). Similarly, central and southern Sierra

Nevada tree-ring studies indicate several medieval

warm-dry intervals and droughts (Curry 1969; Scuderi

1987a, 1993; Hughes and Brown 1992), in particular

one between 840 and 575 cal year BP that overlaps

with the datum from Cliff Lake (Graumlich 1993).

Current Lake Level

5 m

0 1 2 m

Maximum Lake Level, AD 1290 -1340

Stump

Lake Sediments

Granite Substrat e(inferred)

Fig. 3 Idealized profile of

northern portion of Cliff

Lake showing approximate

location of submerged

stump, current lake levels,

and terminal medieval lake

levels

710 J Paleolimnol (2012) 47:707–713

123

Further north, along the Sacramento River, Roos

(2002) and especially Meko et al. (2001) identify

droughts recorded by tree ring chronologies between

810 and 790 cal year BP and between 600 and

550 cal year BP, the latter of course corresponding

to the date at Cliff Lake. These data are corroborated

by sediment cores from the San Joaquin-Sacramento

Delta east of San Francisco Bay (a region document-

ing drainage of over 40% of California) showing an

ostensibly drought-mediated unconformity between

1,670 and 750 cal year BP (Ingram et al. 1996).

Though many Sierra Nevada palynological studies

lack the temporal resolution necessary to focus

specifically on the latest Holocene (Anderson 1990),

pollen cores from ponds and lakes in and around the

range suggest a similar picture. For instance, Power

(1998) identifies medieval droughts and warming at

East Lake, on the western slope of the range, between

approximately 1,500 and 750 cal year BP. More

resolution is available from Pyramid Lake in Nevada,

where Benson et al. (2002) and Mensing et al. (2004)

indentify drought between 650 and 500 cal year BP. A

nearly identical pattern is identified in the oxygen

isotope record of Walker Lake, also in Nevada, with

droughts documented between 690 and 590 cal year

BP (Yuan et al. 2004). Further north, at Diamond Pond

in Oregon, Wigland (1987) reveals an increase in

Sarcobatus pollen likely indicative of drought between

650 and 525 cal year BP. Combined, these proxies

indicate a very general pattern of increased tempera-

ture and decreased precipitation between roughly

1,250 and 550 cal year BP and episodic drought

recorded in multiple regional studies between approx-

imately 690 and 550 cal year BP. Importantly, cessa-

tion of the terminal medieval drought in studies with

sufficient temporal resolution occurs within a very

small range of years (between 600 and 525 cal year

BP), indicating the contemporaneity and similarity of

this phenomenon across a broad geographic expanse.

These data also correspond to the continent-scale

gridded tree-ring drought projections of Cook et al.

(2004) and Herweijer et al. (2007), which identify

several MCA long-term droughts, in particular one ca.

AD 1240–1265 (710–685 cal year BP) that was

roughly contemporaneous with the one recorded at

Cliff Lake. This megadrought is modeled to have

affected most of the western United States save the

Pacific Northwest (i.e., from California’s Mendocino

coast north to Washington state (Cook et al. 2004). A

more recent gridded tree-ring study (Cook et al. 2010) is

even more convincing, showing remarkably close

temporal correlation between California-Nevada tree-

ring recorded droughts and Stine’s (1994) G-1 and G-2

droughts, the latter of course also recorded at Cliff Lake.

There is consequently abundant regional and con-

tinental-scale evidence for a terminal medieval

megadrought between ca. AD 1250 and 1300 and

good evidence, particularly from Cliff Lake, that this

drought affected not only the greater intermountain

west but also the western slope of the south-central

Sierra Nevada. This conclusion calls into question the

perspective that evidence for medieval droughts in the

region could conceivably result from local environ-

mental conditions (Basgall 1999), the most obvious in

this context being the Sierra Nevada rain shadow. That

a medieval lake recession is at least 80 km south of

other well-documented terminal medieval drought

localities (i.e., Mono Lake) and more than 25 km west

of the crest of the range suggests this not to be the case.

Rather, it implies droughts of similar scale and

duration affected much of the Sierra Nevada region

contemporaneously. The Cliff Lake datum thus indi-

cates that terminal medieval lake recessions: (1) have

a greater geographic extent than previously recog-

nized; (2) result from factors other than those of local

geography; and (3) were part of a much larger pattern

of terminal medieval megadroughts across much of

the American West. It thus appears that though late

Holocene California-Nevada paleoclimates were cer-

tainly complex and variable, terminal medieval

megadrought was a widespread, extra-local phenom-

enon affecting, at a minimum, much of interior

California, western Nevada, and southeastern Oregon

for 50 years or more some 600 years ago.

Acknowledgments Research conducted on the Sierra

National Forest and funded, in part, by a dissertation

improvement grant from the University of California, Davis

Institute of Governmental Affairs. G. James West and Robert

Bettinger each provided valuable insight and commentary. Any

errors or omissions, however, are our own.

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