High-Resolution Younger Dryas Environmental Variability:

A Comprehensive Assessment from Mid-North America Tree Rings


P.I. Irina P. Panyushkina and co-P.I. Steven W. Leavitt (Support from NSF ATM-0213696)


 The warming from Late Glacial to Early Holocene was interrupted by an abrupt, millennial-length cold climate excursion known as the Younger Dryas (YD) event.  Effects of this event seem to be widespread, but knowledge of the character of the YD in Europe far exceeds that of other locations such as mid-North America, an area with intimate linkage, via shifting glacial meltwater outlets, to the mechanisms likely to have triggered the event in the mid-N.Atlantic Ocean.  In this study, we are investigating the environmental changes in mid-North America over several millennia (particularly ca. 10,000 to 14,000 14C-yr BP, but including 5,000 to 10,000 BP) during the Late Glacial-Early Holocene transition, including the YD interval, through high-resolution tree-ring methods.  A suite of ten sites with wood of this age has been identified, and numerous additional logs/stumps are being sampled in order to expand the subfossil wood collection already in hand (for 4 sites we already have at least 20 samples) or available from collaborators/cooperators to a size commensurate with the planned investigation. 


Floating ring-width chronologies are being developed for each site/time, using radiocarbon dates to position the sites in the Late Glacial-Early Holocene time frame.  They will not produce a single chronology, but will provide an effective ensemble of chronologies over the 4,000 14C-yr time interval with which to investigate fine-scale climate change.  Contingent on resources, high-resolution environmental information will be extracted at each site/time using ring-width chronologies, event chronologies (eg, frost rings, light rings, reaction wood), stable isotope analysis (dD, d13C and d18O) and xylem anatomy measurements (radial lumen diameter, cell-wall thickness).  Sophisticated spectral analysis techniques will be applied to the ring-width chronologies to estimate frequency of climate-related variability at particular band-widths, especially associated with global teleconnections (eg, ENSO, NAO, PDO, AO).  Finally, high-resolution radiocarbon records will be developed to precisely match existing radiocarbon chronologies by “wiggle matching”, and more importantly to exploit fine-scale differences between existing records from Europe, Japan, Australia and the Cariaco Basin.  Such differences will provide evidence of feedbacks involving ocean ventilation, air-sea interactions and radiocarbon ocean “reservoir” effects, all intimately linked with thermohaline circulation changes.


This systematic study will provide the first high-resolution portrait of the Late Glacial/Early Holocene transition in mid-N. America.  The events and changes of YD time (related to temperature, water-use efficiency, and hydrologic cycle-related parameters of precipitation, relative humidity, and soil saturation) will be measured against those of the periods immediately before and after, and with modern conditions.  The results will better characterize environmental/vegetation changes and responses in mid-North America, place the changes into the context of global changes during deglaciation, and use them to better understand wide-ranging air-ocean changes in this period.  The study conforms closely with current Earth System History program goals to reconstruct paleoclimate variability for intervals of the Holocene in N. America, especially related to (1) abrupt climate change events, (2) climate variability on decadal through millennial time scales (including linkages to ENSO, PDO, NAO, etc.), and (3) atmosphere-ocean-land interaction such as associated with internal forcing by thermohaline circulation.





MAP.  Location of buried wood sites (tree-ring sites)

n- conifer and   l- deciduous wood.

N- new sites, V- vanished sites, P- in press (Panyushkina et al., Radiocarbon 2004)

F1= Fig.1 (2, 3, etc)





Pre-Younger Dryas


Two Creeks (13,500-13,800 Cal y BP)


Fig. 1. Sample Depth of Two Creeks site chronology from 3 collections: 296-year length, 55 trees, Std. Dev. of tree-ring indices 0.22



Younger Dryas


Liverpool East (11,700-12,350 Cal y BP)


Fig. 2. Sample depth of Liverpool site chronology: 131-year length, 19 trees, Std. Dev. of tree-ring indices 0.23

Photo 1,2 . Largest stump (73-cm circumference) in upright position found in 2004 (left) and tilted smaller spruce stumps on east side of drainage ditch (right).



Late- to Post-Younger Dryas


Gribben Basin (11,200-11,600 Cal y BP)


Fig. 3. Sample depth of Gribben Basin site chronology: 178-year length, 32 trees, Std. Dev. of tree-ring indices 0.24



New Sites


Photo 3,4. Mason site, WI: Retention pond excavation adjacent to Amerihost Motel off Mason Road exit of I-43, Green Bay

Red till containing wood of apparent Two Creeks equivalence above very sandy grey till or lake sediment (left). Spruce logs scraped by excavator (right).


Photo 5,6. Brewster site, IL: 12,800-13,000 Cal y BP

Removing irrigation tiles from abandoned fields in W. Chicago area (left).
Ditch profile with two layers of buried peat with wood (right). (photos by M. Zoellner)


Fig. 4. Averaged series: 65-year length, 7 tree-ring series from 3 trees, Std. Dev. of tree-ring indices 0.57



Vanished Site


Photo 7,8. Brown's Sand Pit site, IN: 13,500 Cal y BP exposure overgrown between Sept. 1987 (left) and in Jun. 2004 (right).

[The photos were taken from near the same position in 1987 and 2004 (the E-W oriented water ditch appears in both photos). The slope with TwoCreekan wood exposure is marked with red line.]



In Press


Photo 9. Lincoln Quarry, IL (log 6,320 BP)



Publications and Presentations: 


Panyushkina, I.P. and Leavitt, S.W., 2003. Tree-ring investigation of the Younger Dryas in the U.S. Upper Midwest. XVI INQUA Congress, Reno, NV, 23-30 July.


Panyushkina, I.P. and Leavitt, S.W., 2004. High-resolution records of the Pleistocene-Holocene transition from tree rings in central North America. American Quaternary Association Biennial Meeting, Lawrence, Kansas, 26-28 June 2004.


Panyushkina, I.P., Leavitt, S.W. and Noggle, S., 2002. A tree-ring study of wood of possible Younger Dryas age from central Illinois. 6th International Conference on Dendrochronology, Quebec City, Canada, 22-27 August.


Panyushkina, I.P., Leavitt, S.W., Wiedenhoeft, A., Noggle S., Curry B. and Grimm, A., 2004. Tree-ring records of near-Younger Dryas time in Central N. America- Preliminary results from the Lincoln Quarry site, central Illinois, USA. Radiocarbon In Press.


Leavitt, S. and Panyushkina, I., 2003. Tree-ring records of near-Younger Dryas time in the U.S. Upper Midwest. 18th International Radiocarbon Conference, Wellington, New Zealand, 1-5 September 2003.

 [updated July 15, 2004]