Person: Huybers, Peter
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Huybers
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Peter
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Huybers, Peter
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Publication Origin of spatial variation in US East Coast sea-level trends during 1900–2017(Springer Science and Business Media LLC, 2018-12) Piecuch, Christopher G.; Huybers, Peter; Hay, Carling C.; Kemp, Andrew C.; Little, Christopher M.; Mitrovica, Jerry; Ponte, Rui M.; Tingley, Martin P.Identifying the causes of historical trends in relative sea level—the height of the sea surface relative to Earth’s crust—is a prerequisite for predicting future changes. Rates of change along the eastern coast of the USA (the US East Coast) during the past century were spatially variable, and relative sea level rose faster along the Mid-Atlantic Bight than along the South Atlantic Bight and the Gulf of Maine. Past studies suggest that Earth’s ongoing response to the last deglaciation surface redistribution of ice and water and changes in ocean circulation contributed considerably to this large-scale spatial pattern. Here we analyse instrumental data and proxy reconstructions using probabilistic methods to show that vertical motions of Earth’s crust exerted the dominant control on regional spatial differences in relative sea-level trends along the US East Coast during 1900–2017, explaining most of the large-scale spatial variance. Rates of coastal subsidence caused by ongoing relaxation of the peripheral forebulge associated with the last deglaciation are strongest near North Carolina, Maryland and Virginia. Such structure indicates that Earth’s elastic lithosphere is thicker than has been assumed in other models. We also find a substantial coastal gradient in relative sea-level trends over this period that is unrelated to deglaciation and suggests contributions from twentieth-century redistribution of ice and water. Our results indicate that the majority of large-scale spatial variation in long-term rates of relative sea-level rise on the US East Coast is due to geological processes that will persist at similar rates for centuries.Publication Slow Climate Mode Reconciles Historical and Model-Based Estimates of Climate Sensitivity(American Association for the Advancement of Science (AAAS), 2017-07) Proistosescu, Cristian; Huybers, PeterEstimates of climate sensitivity from models and observations are reconciled by accounting for slowly responding climate mode. The latest Intergovernmental Panel on Climate Change Assessment Report widened the equilibrium climate sensitivity (ECS) range from 2° to 4.5°C to an updated range of 1.5° to 4.5°C in order to account for the lack of consensus between estimates based on models and historical observations. The historical ECS estimates range from 1.5° to 3°C and are derived assuming a linear radiative response to warming. A Bayesian methodology applied to 24 models, however, documents curvature in the radiative response to warming from an evolving contribution of interannual to centennial modes of radiative response. Centennial modes display stronger amplifying feedbacks and ultimately contribute 28 to 68% (90% credible interval) of equilibrium warming, yet they comprise only 1 to 7% of current warming. Accounting for these unresolved centennial contributions brings historical records into agreement with model-derived ECS estimates.Publication Combined Influence of Soil Moisture and Atmospheric Evaporative Demand Is Important for Accurately Predicting US Maize Yields(Springer Science and Business Media LLC, 2020-02-18) Rigden, A. J.; Mueller, N. D.; Holbrook, N. M.; Pillai, Natesh; Huybers, PeterUnderstanding the response of agriculture to heat and moisture stress is essential to adapt food systems under climate change. Although evidence of crop yield loss with extreme temperature is abundant, disentangling the roles of temperature and moisture in determining yield has proven challenging, largely due to the limited soil moisture data and the tight coupling between moisture and temperature at the land surface. Here, using well-resolved observations of soil moisture from the recently launched Soil Moisture Active Passive satellite, we quantified the contribution of imbalances between atmospheric evaporative demand and soil moisture to maize yield damages in the U.S. Midwest. We show that retrospective yield predictions based on the interactions between atmospheric demand and soil moisture significantly outperform those using temperature and precipitation singly or together. The importance of accounting for this water balance is highlighted by the fact that climate simulations uniformly predict increases in atmospheric demand during the growing season but root-zone soils that are variously drier or wetter. A damage estimate conditioned only on simulated changes in atmospheric demand, as opposed to also accounting for changes in soil-moisture, would erroneously indicate approximately twice the damage. This research demonstrates that more accurate predictions of maize yield can be achieved by using soil moisture data and indicates that accurate estimates of how climate change will influence crop yields requires explicitly accounting for variations in water availability.Publication Detection of a Dynamic Topography Signal in Last Interglacial Sea-Level Records(American Association for the Advancement of Science (AAAS), 2017-07-07) Austermann, Jacqueline; Mitrovica, Jerry; Huybers, PeterEstimating minimum ice volume during the last interglacial based on local sea-level indicators requires that these indicators are corrected for processes that alter local sea level relative to the global average. Although glacial isostatic adjustment is generally accounted for, global scale dynamic changes in topography driven by convective mantle flow are generally not considered. We use numerical models of mantle flow to quantify vertical deflections caused by dynamic topography and compare predictions at passive margins to a globally distributed set of last interglacial sea-level markers. The deflections predicted as a result of dynamic topography are significantly correlated with marker elevations (>95% probability) and are consistent with construction and preservation attributes across marker types. We conclude that a dynamic topography signal is present in the elevation of last interglacial sea-level records and that the signal must be accounted for in any effort to determine peak global mean sea level during the last interglacial to within an accuracy of several meters.Publication The Influence of True Polar Wander on Glacial Inception in North America(Elsevier BV, 2017-03) Daradich, A; Huybers, Peter; Mitrovica, Jerry; Chan, N; Austermann, JThe impact that long-term changes in Earth's rotation axis relative to the surface geography, or true polar wander (TPW), and continental drift have had in driving cooling of high-latitude North America since the Eocene is explored. Recent reanalyses of paleomagnetic pole positions suggest a secular drift in Earth's rotation axis of over the last 40 Myr, in a direction that has brought North America to increasingly higher latitudes. Using modern temperature data in tandem with a simple model, a reduction in the annual sum of positive degree days (PDDs) driven by this polar and plate motion over the last 20 Myr is quantified. At sites in Baffin Island, the TPW- and continental drift-driven decrease in insolation forcing over the last 20 Myr rivals changes in insolation forcing caused by variations in Earth's obliquity and precession. Using conservative PDD scaling factors and an annual snowfall equal to modern station observations, the snowiest location in Baffin Island 20 Myr ago had a mass balance deficit of ∼0.75–2 m yr−1 (water equivalent thickness) relative to its projected mass balance at 2.7 Ma. This mass balance deficit would have continued to increase as one goes back in time until ∼40 Myr ago based on adopted paleopole locations. TPW and continental drift that moved Arctic North America poleward would have strongly promoted glacial inception in Baffin Island at ∼3 Ma, a location where the proto-Laurentide Ice Sheet is thought to have originated.Publication Global Relationships between Cropland Intensification and Summer Temperature Extremes over the Last 50 Years(American Meteorological Society, 2017-09) Mueller, Nathaniel; Rhines, Andrew; Butler, Ethan; Ray, Deepak; Siebert, Stefan; Holbrook, Noel; Huybers, PeterConversion of native ecosystems to cropland and the use of irrigation are considered dominant pathways through which agricultural land-use change alters regional climate. Recent research proposes that increases in cropland productivity, or intensification, also influences climate through increasing evapotranspiration. Increases in evapotranspiration are expected to have the greatest temperature influence on extremely hot summer days with high vapor pressure deficits. Here, the generalizability and importance of such relationships are assessed by examining historical land-use and climate trends in seven regions across the globe, each containing a major temperate or subtropical cropping area. Trends in summer high-temperature extremes are sequentially compared against trends in cropland area, area equipped for irrigation, precipitation, and summer cropping intensity. Trends in temperature extremes are estimated using quantile regression of weather station observations, and land-use data are from agricultural inventories and remote sensing. Intensification is the best predictor of trends in extreme temperatures among the factors that are considered and is generally associated with trends that are 0.2°–0.4°C decade−1 cooler than in adjacent regions. Neither cropland area nor precipitation trends are systematically associated with extreme temperature trends across regions, although high temperatures are suppressed over those portions of central North America and East Asia experiencing growth in irrigation. Both the temperature trends associated with intensification and increased irrigation can be understood as a consequence of increased latent cooling. These results underscore that the weather experienced by crops is not entirely external but also depends on agricultural practices.Publication Climate Change and Global Food Systems: Potential Impacts on Food Security and Undernutrition(Annual Reviews, 2017) Myers, Samuel; Smith, Matthew; Guth, Sarah; Golden, Christopher; Vaitla, Bapu; Mueller, Nathaniel; Dangour, Alan D.; Huybers, PeterGreat progress has been made in addressing global undernutrition over the past several decades, in part because of large increases in food production from agricultural expansion and intensification. Food systems, however, face continued increases in demand and growing environmental pressures. Most prominently, human-caused climate change will influence the quality and quantity of food we produce and our ability to distribute it equitably. Our capacity to ensure food security and nutritional adequacy in the face of rapidly changing biophysical conditions will be a major determinant of the next century's global burden of disease. In this article, we review the main pathways by which climate change may affect our food production systems—agriculture, fisheries, and livestock—as well as the socioeconomic forces that may influence equitable distribution.Publication Earth rotation changes since ?500 CE driven by ice mass variations(Elsevier BV, 2016) Hay, Carling; Mitrovica, Jerry; Morrow, Eric; Kopp, Robert E.; Huybers, Peter; Alley, Richard B.We predict the perturbation to the Earth's length-of-day (LOD) over the Common Era using a recently derived estimate of global sea-level change for this time period. We use this estimate to derive a time series of “clock error”, defined as the difference in timing of two clocks, one based on a theoretically invariant time scale (terrestrial time) and one fixed to Earth rotation (universal time), and compare this time series to millennial scale variability in clock error inferred from ancient eclipse records. Under the assumption that global sea-level change over the Common Era is driven by ice mass flux alone, we find that this flux can reconcile a significant fraction of the discrepancies between clock error computed assuming constant slowing of Earth's rotation and that inferred from eclipse records since 700 CE. In contrast, ice mass flux cannot reconcile the temporal variability prior to 700 CE.Publication The changing shape of Northern Hemisphere summer temperature distributions(Wiley-Blackwell, 2016) McKinnon, Karen A.; Rhines, Andrew; Tingley, Martin P.; Huybers, PeterThe occurrence of recent summer temperature extremes in the midlatitudes has raised questions about whether and how the distributions of summer temperature are changing. While it is clear that in most regions the average temperature is increasing, there is less consensus regarding the presence or nature of changes in the shape of the distributions, which can influence the probability of extreme events. Using data from over 4000 weather stations in the Global Historical Climatology Network-Daily database, we quantify the changes in daily maximum and minimum temperature distributions for peak summer in the Northern Hemisphere midlatitudes during 1980–2015 using quantile regression. A large majority (87–88%) of the trends across percentiles and stations can be explained by a shift of the distributions with no change in shape. The remaining variability is summarized through projections onto orthogonal basis functions that are closely related to changes in variance, skewness, and kurtosis. North America and Eurasia show significant shifts in the estimated distributions of daily maximum and minimum temperatures. Although no general change in summer variance is found, variance has regionally increased in Eurasia and decreased in most of North America. Changes in shape that project onto the skewness and kurtosis basis functions have a much smaller spatial scale and are generally insignificant.Publication Comment on "Sensitivity of Seafloor Bathymetry to Climate-Driven Fluctuations in Mid-Ocean Ridge Magma Supply"(American Association for the Advancement of Science (AAAS), 2016) Huybers, Peter; Langmuir, Charles; Katz, Richard; Ferguson, D.; Proistosescu, Cristian; Carbotte, S.Recent studies have proposed that the bathymetric fabric of the seafloor formed at mid-ocean ridges records rapid (23,000 to 100,000 years) fluctuations in ridge magma supply caused by sealevel changes that modulate melt production in the underlying mantle. Using quantitative models of faulting and magma emplacement, we demonstrate that, in fact, seafloor-shaping processes act as a low-pass filter on variations in magma supply, strongly damping fluctuations shorter than about 100,000 years. We show that the systematic decrease in dominant seafloor wavelengths with increasing spreading rate is best explained by a model of fault growth and abandonment under a steady magma input. This provides a robust framework for deciphering the footprint of mantle melting in the fabric of abyssal hills, the most common topographic feature on Earth.