Huybers and Wunsch, Paleo-Physical Oceanography with an Emphasis on Transport Rates, Annual Review of Marine Science, in press. pdf
Perron and Huybers, Is there an orbital signal in the
polar layered deposits on Mars? , Geology, 2009. pdf and a news piece
Stine, Huybers, and Fung, Changes in the phase of the
annual cycle of surface temperature , Nature,
2009. pdf, supplementary information,
and
a news piece
Huybers and Denton, Antarctic temperature at orbital time
scales controlled by local summer duration, Nature Geoscience, 2008.
pdf and
supplementary material
Huybers and Tziperman, Integrated summer insolation
forcing and 40,000 year glacial cycles: the perspective from an
icesheet/energy-balance model, Paleoceanography, 2008.
pdf and
code
Huybers and Molnar, Tropical cooling and the onset of
North American glaciation, Climate of the Past, 2007.
pdf
Huybers, Gebbie, and Marchal, Can paleoceanographic
tracers constrain meridional circulation rates?, Journal of Physical Oceanography, 2007.
pdf
Huybers, Glacial variability over the last 2Ma: an
extended depth-derived agemodel, continuous obliquity pacing, and
the Pleistocene progression, Quaternary Science Reviews, 2007.
pdf and supplemental material (also posted at NCDC)
Gebbie and Huybers, Meridional circulation
during the Last Glacial Maximum explored through a combination of
South Atlantic d18O observations and a geostrophic inverse model,
G-cubed, 2006.
pdf
Tziperman, Raymo, Huybers, and Wunsch, Consequences of
pacing the Pleistocene 100 kyr ice ages by nonlinear phase locking to
Milankovitch forcing, Paleoceanography, 2006. pdf
Huybers and Curry, Links between annual,
Milankovitch, and continuum temperature variability, Nature,
2006. pdf and supplemental material
Huybers, comment on ``Hockey sticks, principal
components, and spurious significance'' by McIntyre and McKitrick
[2005], Geophysical Research Letters, 2005. pdf and supplemental material (An edited version of
this paper was published by AGU. Copyright 2005 American Geophysical
Union.)
Huybers and Wunsch, Obliquity pacing of the late Pleistocene
glacial terminations, Nature,
2005. pdf
Huybers and Wunsch, A depth-derived Pleistocene
age-model: uncertainty estimates, sedimentation variability, and
nonlinear climate change, Paleoceanography, 2004. pdf
Huybers, Comments on: 'Coupling of the hemispheres in
observations and simulations of glacial climate change': by
A. Schmittner, O.A. Saenko, and A.J. Weaver [Quaternary Science
Reviews 22 (2003) 659-671], Quaternary Science Reviews,
2004. pdf
Huybers and Wunsch, Rectification and precession-period
signals in the climate system, Geophysical Research Letters, 2003. pdf
Manuscripts
Gebbie and Huybers, Resolving the spectrum of ocean water masses, submitted.
pdf
Tingley and Huybers, A Bayesian algorithm for reconstructing spatially arrayed temperatures. Part 1: Development and applications to paleoclimate reconstruction problems, submitted (pdf). A zipped package of Matlab files that implements the method can be downloaded from
Martin's website.
Tingley and Huybers, A Bayesian algorithm for reconstructing spatially arrayed temperatures. Part 2: Behavior and comparison with the regularized expectation-maximization algorithm, submitted.
pdf
Haam and Huybers, A test for the presence of covariance between time-uncertain series of data with application to the Donge Cave speleothem and atmospheric radiocarbon records, submitted.
pdf
Huybers, Pleistocene glacial variability as a chaotic response to obliquity
forcing , submitted.
pdf
Huybers and Langmuir, Feedback between deglaciation,
volcanism, and atmospheric CO2 , submitted.
pdf
Tingley and Huybers, The spatial mean and dispersion of surface temperatures
over the last 1200 years: warm intervals are also variable
intervals , submitted.
pdf
Research
Glacial cycles. Over the last three million years the amount
of ice on the Earth has alternately waxed so as to cover much of the
northern continents and waned to the relatively ice-free conditions we
have today. The cause of these massive shifts in climate remains
unclear, not for lack of hypotheses, of which there are many, but
instead for lack of any single compelling theory. Thus, one aim is to
distinguish between the many competing glacial hypotheses (HW05).
Another aim is to explore the causes of glaciation during the Pliocene
and early Pleistocene, associated with seemingly more simple 40,000
year variations in ice-volume
(H06,
HT08). It appears clear that changes in Earth's obliquity pace
glacial cycles (HW05,
H07),
and am working on testing the extent to which the precession of the
equinoxes is also involved. High resolution imagery and topography
from Mars offers another test and perspective on our understanding of
the orbital influence on glaciation, though the results we can arrive
at with present data are far from definitive
(PH09).
It has become increasingly clear that we will not understand the
glacial cycles until we also understand the accompanying changes in
atmospheric CO2. The glacial/interglacial changes in CO2 may not only
involve the organic and marine carbon pools, but also the vast
reservoir of carbon in Earth's interion, in that glacial unloading
appears to radically increase global volcanic activity during the
deglaciation and, thus, volcanic emissions of
CO2
(HL_submitted). Further examples of interactions between
glaciation and other parts of Earth's climate include that the
initiation of Northern Hemisphere glaciation may have been caused by
long term cooling in the Eastern Equatorial Pacific
(e.g.~HM07),
and that Antarctica's response to insolation forcing seems to mirror
and may reinforce the Northern response
(HD08).
The annual cycle. The annual cycle in surface temperature is
massive, larger than even the glacial-interglacial cycles in most
places on Earth, and even small changes in its amplitude and timing
can have large consequences. It appears that over the last fifty
years the annual cycle on land has been trending earlier
(SHF_2009),
a shift not reproduced by any of the IPCC models, and possibly related
to surface drying, shifts in atmospheric circulation, or changes in
the absorptivity of the atmosphere. Changes in Earth's orbital
configuration also alter Earth's annual cycle of insolation. For
example, the precession of the equinoxes acts to modulate both the
duration of the seasons and the associated intensity of solar
insolation. Counter-balancing between these two precessional effects
may account for the apparent lack of precession-period variability in
ice volume during the early Pleistocene
(H06).
Note that variations in how the seasonal cycle is recorded in the
climate record can also strongly influence that record
(HW03).
Climatic variations spanning timescales from months to centuries also
appear related to the annual cycle, following a power-law relationship
which is itself proportional the amplitude of the annual cycle
(HC06).
Reconstruction of past climate states. Instrumental records
of climate are increasingly sparse back in time, so that tracing out
the history of past temperature variability requires the use of
climate proxies, derived from ice, rock, sediment, and biological
records. How best to determine spatial average quantities, such as
temperature, from these proxies has been the subject of some debate
(e.g. H05).
Martin Tingley and I are working on a Bayesian Hierarchical model to
estimate spatial average temperature from noisy proxies of local
temperature variability (TH_submitted
part
1,
part
2). Another topic of inquiry is to understand how changes in the
mean temperature correspond with its variability
(TH_submitted).
Similarly, reconstruction of the past ocean state allows us to gage
the natural range and modes of ocean circulation, in principle permits
testing of our models over a wider range of conditions, and helps
place modern changes in context, but is challenging
(e.g. HGM06,
GH07).
Jake Gebbie and I are in the process of combining a wide array of
modern and paleoceanographic observations to understand how the
distribution of the ocean's water mass properties has shifted through
time
(GH_submitted),
and are now also exploring the disequilibrium of modern ocean
temperatures. A review with Carl Wunsch of the rates of ocean
circulation during the Last Glacial Maximum was recently completed
(HW_inpress).
Time uncertainty. Time-uncertainty is ubiquitous and of a
degree which cannot be ignored in many paleoclimate and geologic
applications. One theme has been to develop a chronology of
Pleistocene glaciation which is independent of orbital assumptions
(HW04,
H07),
along with estimates of the associated time-uncertainty. Another
theme is to explore how time uncertainty will bias or obscure
statistical analysis of the climate record
(HW04,
PH09).
Eddie Haam has developed an extreme value method to test for the
relationship between time-uncertain records
(HH_submitted).
The handling of time-uncertainty seems one of the more pressing, yet
less developed, problems in paleoclimate.
Statistical Methods. To make progress on the above problems
we've found it useful to develop various statistical techniques. Jake
Gebbie developed a Total Matrix Inversion method
(TMI,
almost too much information) that estimates how every point in the
ocean relates to every other point from a wide variety of tracer data,
and permits for exploration of ocean transport, heat and carbon
uptake, and transit times. Martin Tingley developed a Bayesian
Algorithm for Reconstructing Spatially Arrayed Temperatures
(BARSAT,
so named in envy of classmates who work on satellites) that permits
for combining instrumental and various proxy data to determine past
temperature fields, and which is being extended to include
precipitation and other climate variables. Eddie Haam developed a
test for the Maximum Covariance between Time uncErtain Series
(MCTEST,
which speaks for itself) for assessing whether time-uncertain proxy
records are related to one another.
