MIDGE-BASED AIR TEMPERATURE INFERENCE MODEL PROVIDES EVIDENCE FOR PEAK
HOLOCENE WARMTH AT ~ 5200 YR BP IN THE EASTERN GREAT BASIN, USA
David Porinchu, Scott Reinemann, Bryan Mark and Jason Box
Department of Geography, The Ohio State University
Introduction
Study Site and Methodology
•Changes to hydrology arguably comprise the most critical potential
impact of climate change to the Intermountain West of the United
States.
• A 328 cm sediment core was recovered from Stella Lake, a small
•Great Basin National Park (GBNP) exemplifies the heightened concern
over present and future water availability in this region given a
proposed pipeline project to supply growing population centers in the
south.
• The sediment-water interface appeared to be undisturbed during
sediment recovery, suggesting the uppermost sediment was obtained
(~ 3ha), shallow (2.5m), high elevation (3,150m) lake in August 2007
• The major taxa comprising the mid-Holocene midge community
are: Corynoneura/Theinemaniella, Procladius and Tanytarsus;
the late-Holocene Cladotanytarsus is replaced by
Psectrocladius semicirculatus, TAH and Tanytarus
• The midge-based MJAT inference reveals that peak Holocene
warmth, ~ 11oC, occurred at ~ 5200 years BP (Fig. 8)
• The interval between 5100 yr BP and 1800 yr BP was
characterized by a gradual decrease in MJAT; core minima of
9oC occurred at 1800 yr BP
•The remains of midge flies (Fig. 1), preserved in the lake sediment of
Stella Lake, a small climatically sensitive lake located in GBNP were
used to quantitatively reconstruct long-term changes in the
temperature regime of the region
Fig. 5 Stella Lake, Great Basin N. P. (August 2007) (photo credit S. Reinemann)
• Chronological control is provided by four 14C AMS dates on
terrestrial macro-fossils (Table 1)
• MJAT increased relatively rapidly in the post-1800 interval;
core maxima of 11.1oC occurs at ~ 100 yr BP
VMP
• Sub-fossil midge remains were identified and enumerated
(n = 100, ~ 20 year resolution)
Fig.1: Photomicrograph of a Dicrotendipes
head capsule (scale bar is 50 μm). VMP =
ventromental plate
Fig.2: Location of Great Basin training set
lakes, Great Basin N.P. and Stella Lake.
MJAT acquired from the PRISM Group,
Oregon State University.
• Applied the WA-PLS midge-based inference model for MJAT
to the sub-fossil midge assemblages (Fig. 7)
Great Basin Chironomid Training Set
•A chironomid calibration set was developed for the Great Basin (Fig. 2)
Fig. 8 LOI and midge-inferred MJAT reconstruction for Stella Lake, NV
•Redundancy analysis (RDA) and variance partitioning revealed that
summer surface water temperature (SSWT) and mean July air
temperature (MJAT) could account for a statistically significant and
independent amount of variance in midge community composition
•The chironomid-based inference models for SSWT and MJAT were
based on a weighted-averaging-partial least squares approach (WA-PLS)
(Figs. 3 & 4)
Table 1: Radiocarbon data for Stella Lake
Results and Discussion
• The initial midge community is dominated by Psectrocladius
semicirculatus type, Chironomus, TAG and Tanytarsus
Conclusions
• A number of sites in the Great Basin record warmer
and/or drier conditions than at present between 5400
and 5000 cal yr BP (references)
• Refining our understanding of the forcing factors
responsible for this event and its manifestation in the
Great Basin may improve climate projections for the
future
r2 = 0.54
RMSEP = 1.0oC
N = 79
• future research will focus on basin-wide hydro-climatic
modeling and will begin to describe secondary ecological
responses to future climate change.
Fig. 3 Relationship between observed
and predicted SSWT
Fig. 4 Relationship between observed
and predicted MJAT
Fig. 7 Chironomid Percentage Diagram for Stella Lake, NV
Acknowledgements: We thank Gretchen Baker, Ecologist (GBNP) and Park
Superintendent, Cindy Nielsen for facilitating our research and providing access to
the research site. We are grateful to Jim DeGrand, Karin Bumbaco, Erica Harris
(OSU Geography) and Adam Herrington (OSU Earth Sciences) for their help in the
field. Funding for this research was provided by the National Science Foundation
(ATM-0437433), The Western National Parks Association (WNPA) and the OSU
Dept. of Geography