ReconstructionHow did climate vary?
- Liebig's Law is a basic ecological principal, stating that growth is determining by whatever environmental factor is limiting. Zan Stine has been inquiring into whether this principal holds at the level of individual trees and, if so, what are the implications for how best to reconstruct past temperatures from such trees? In an initial paper, we find some strong evidence for the operation of Liebig's Law at the level of individual trees in the Arctic, and suggest that temperatures reconstructions can be improved by using those trees that are growing relatively faster on a given year (2017).
- Thomas Laepple showed that spectral estimates of Mg/Ca and alkenone sea surface temperature variability records can be brought into consistency with one another once measurement noise, bioturbation, and aliasing are accounted for (2013). The results are also consistent with estimates of regional sea surface temperature variability available from instrumental records (2014). Having established some consistency between streams of proxy and instrumental data, we then compared regional sea surface temperature variability against coupled ocean-atmosphere model simulations and find big differences, where the models have nearly an order of magnitude less regional variability at centennial and millennial timescales (2014). These results imply that regional climate change is more variable than typically predicted.
- Andy Rhines implemented a Lagrangian tracer algorithm in order to explore source properties of Greenland snow accumulation within simulation of Pre-Industrial and Last Glacial Maximum. He demonstrates that the Lagrangian algorithm is complimentary to more-standard Eularian tracer approaches but offers higher resolution than is conventionally attainable. These high-resolution results show that much of Greenland's simulated accumulation during the Last Glacial Maximum is sourced from near the sea ice edge because of the combined effects of extensive sea ice and steering of the storm track by the Laurentide ice sheet (2014).
- Zan Stine demonstrated a strong correspondence between patterns of light limitation and the amplitude of Arctic tree ring responses to volcanic forcing. Furthermore, a similar correspondence exists between light limitation and the so-called divergence between tree ring records and surface temperature. We argue that tree ring divergence results from the dimming of shortwave radiation reaching the surface beginning in about 1955 (2014). Martin Tingley then led a study showing that tree ring reconstructions overestimate the response to volcanoes when interpreted strictly as recording temperature variations in comparison with instrumental records. This overestimate is greatest in Arctic regions with the lowest light availability, consistent with tree ring density responding to both cooling and decreased light following a volcanic eruption (2014). These results complicate the interpretation of tree ring records, but also suggest the possibility of reconstructing past changes in surface light availability.
- Martin Tingley constructed a Bayesian Hierarchical model to estimate spatial average temperature from noisy proxies of local temperature variability (2010a, 2010b). Application of this model to Arctic climate proxies demonstrates that recent temperatures are unprecedented over the last 600 years (2013). In other work, Martin has shown that the spatial variability of temperatures is greater during the Medieval Warm Period and recent decades than during the Little Ice Age (2015).
- A complimentary line of work is to reconstruct past ocean states, allowing us to better gage the natural range and modes of ocean circulation and, in principle, test models under different climate conditions (2006, 2007, and 2010). Jake Gebbie developed a technique for tracing ocean water masses and applied it to modern observations in order to quantify different water masses (2010), how they are filled from the surface ocean (2011a), and to better interpret radiocarbon observations (2011b). Jake has also gone on to apply these methods to interpreting circulation during the Last Glacial Maximum.
- Stine and Huybers Implications of Liebig's law of the minimum for tree-ring reconstructions of climate, Environmental Research Letters, early online release, 2017. link, pdf
- Tingley and Huybers Heterogeneous warming of Northern Hemisphere surface temperatures over the last 1200 years, Journal of Geophysical Research - Atmospheres, 2015. pdf
- Laepple and Huybers Ocean surface temperature variability: Large model-data differences at decadal and longer periods, PNAS, 2014. pdf
- Laepple and Huybers Global and regional variability in marine surface temperatures, Geophysical Research Letters, 2014. pdf
- Laepple and Huybers Reconciling discrepancies between Uk37 and Mg/Ca reconstructions of Holocene marine temperature variability, Earth and Planetary Science Letters, 2013. pdf
- Rhines and Huybers Sea ice and dynamical controls on pre-industrial and Last Glacial Maximum accumulation in central Greenland, Journal of Climate, 2014. pdf
- Stine and Huybers Arctic tree rings as recorders of variations in light availability, Nature Communications, 2014. pdf
- Tingley, Stine, and Huybers Temperature reconstructions from tree-ring densities overestimate volcanic cooling, Geophysical Research Letters, 2014. pdf
- Tingley and Huybers Recent temperature extremes at high northern latitudes unprecedented in the past 600 years, Nature, 2013. pdf data and code
- Tingley and Huybers, A Bayesian Algorithm for Reconstructing Climate Anomalies in Space and Time. Part 1: Development and applications to paleoclimate reconstruction problems, Journal of Climate, 2010 pdf
- Tingley and Huybers, A Bayesian Algorithm for Reconstructing Climate Anomalies in Space and Time. Part 2: Comparison with the regularized expectation-maximization algorithm, Journal of Climate, 2010. pdf
- Gebbie and Huybers The mean age of ocean waters inferred from radiocarbon observations: upper and lower bounds, sensitivity to surface sources and accounting for mixing histories, Journal of Physical Oceanography, 2012. pdf
- Gebbie and Huybers, How is the ocean filled?, Geophysical Research Letters, 2011. pdf
- Gebbie and Huybers, Total Matrix Intercomparison: a method for determining the geometry of water-mass pathways, Journal of Physical Oceanography, 2010. pdf
- Huybers, Gebbie and Marchal Can paleoceanographic tracers constrain meridional circulation rates?, Journal of Physical Oceanography, 2007. pdf
- 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
- Huybers and Wunsch, Paleo-Physical Oceanography with an Emphasis on Transport Rates, Annual Review of Marine Science, 2010. pdf