Publications

Journal articles

2024

1. 

   Climate-Driven Topographic Asymmetry Enhanced by Glaciers: Implications for Drainage Reorganization in Glacial Landscapes

   Jingtao Lai, and Kimberly Huppert

   Geophysical Research Letters, 2024

   Abstract DOI

   Climate contrasts across drainage divides, such as orographic precipitation, are ubiquitous in mountain ranges, and as a result, mountain topography is often asymmetric. During glacial periods, these climate gradients can generate asymmetric glaciation, which may modify topographic asymmetry and drive divide migration during glacial-interglacial cycles. Here we quantify topographic asymmetry caused by asymmetric glaciation and its sensitivity to different climate scenarios. Using an analytical model of a steady-state glacial profile, we find that the degree of topographic asymmetry is primarily controlled by differences in the equilibrium line altitude across the divide. Our results show that glacial erosion can respond to the same climate asymmetry differently than fluvial erosion. When there are precipitation differences across the divide, glacial erosion produces greater topographic asymmetry than fluvial erosion, all else equal. These findings suggest that glaciations may promote drainage reorganization and landscape transience in intermittently glaciated mountain ranges.

2. Numerical modelling of coupled climate, tectonics, and surface processes on the eastern Himalayan syntaxis

   Xueyun Lu, Jingtao Lai, Lining Wang, Jianqing Ji, and Dalai Zhong

   Earth-Science Reviews, 2024

   Abstract DOI

   The geosphere dynamics near Earth’s surface is a key scientific issue for understanding how Earth system works. However, the specific mechanisms underlying the interplay between these geospheres still remain unclear. Here, we take the eastern Himalayan syntaxis, the most typical region undergoing ferocious geosphere interplay on the planet, as our primary research area. We incorporated a topography-dependent precipitation model into traditional geomorphological-thermomechanical modelling and conducted over 200 experiments to investigate the interplay between climate, tectonics, and surface processes during the evolution of the orogenic wedge. The results show that a distinct type of orogenic wedge emerges when the convergence rate and average precipitation fall within specific ranges determined by the crustal geothermal field. Within this type of orogenic wedge, a sustained, stationary, localized and relatively rapid erosion process can be established on the windward flank. This can further induce sustained and rapid uplift of rocks, exhumation and deformation, forming a large-scale antiform, which exhibits a certain degree of similarity to the eastern Himalayan syntaxis. We propose that the formation of the eastern Himalayan syntaxis share this similar mechanism. Our analysis of the results indicates that the influences of climatic forcing, tectonic forcing, and geothermal field on the evolution of orogenic wedge can be integrated into a single parameter (EF), and we propose that 0.24≤EF≤0.45 is a necessary condition for the development of a syntaxis, which provides a quantitative constraint on the formation of a syntaxis for the first time.

2023

1. Sediment Dynamics Control Transient Fluvial Incision - Comparison of Sediment Conservation Schemes in Models of Bedrock-Alluvial River Channel Evolution

   Jingtao Lai, Kimberly Huppert, and Jean Braun

   ESS Open Archive, 2023

   Preprint

   DOI

2. 

   Asymmetric Glaciation, Divide Migration, and Postglacial Fluvial Response Times in the Qilian Shan

   Jingtao Lai, and Kimberly Huppert

   Geology, 2023

   Abstract DOI

   Glacial-interglacial cycles have repeatedly perturbed climate and topography in many midlatitude mountain ranges during the Quaternary. Glacial erosion can move drainage divides and induce fluvial adjustments downstream, yet the time scale over which these adjustments occur remains unclear. We examined landscape evolution in the northwest-southeast–trending Qilian Shan, where the contrast in solar insolation between north- and south-facing slopes has generated larger glaciers on the northern range crest. Our analyses suggest that this asymmetric glaciation has caused southward migration of the main drainage divide, prompting river channels below the extents of ice on north-facing slopes to become oversteepened for their drainage area and channels on south-facing slopes to become analogously understeepened. These changes in steepness should accelerate or slow down postglacial fluvial incision, even in the regions where topography has not been directly modified by glacial erosion. Numerical modeling suggests these discrepancies persist for millions of years, much longer than the duration of recent glacial-interglacial cycles, implying a widespread and enduring influence of intermittent glaciations on landscape evolution in glaciated mountain ranges during the Quaternary.

3. Numerical Examination of the Geomorphic Indicators for Lateral Fold Growth

   Lin Gao, Chuanqi He, Gang Rao, Ci-Jian Yang, Xiaoping Yuan, Jingtao Lai, Pengcheng Tang, and Lei Wu

   Geomorphology, 2023

   Abstract DOI

   Fold-and-thrust belts (FTBs) develop widely in and around active orogenic belts on Earth. With the accumulation of structural shortening, thrust-related folds can grow by increasing their amplitudes and lengths, providing insights into the structural evolution of FTBs. Investigations of fold growth patterns and landscape responses through time and space have important implications for hydrocarbon exploration and geo-hazard assessment. Evidence for lateral fold propagation (i.e., increase in length) usually comes from geochronological constraints based on differences in onset timings along strike. However, these traditional methods are time consuming and economically costly. Alternatively, previous studies have proposed the use of geomorphic features to investigate the lateral fold propagation, including spatial variations in the patterns and densities of river channels, the configuration of the topographic profile along the fold crest, and the occurrence of wind gaps. However, such analyses are based on morphological features of present-day landscapes, which still need process-based validations. Here, we conduct a series of landscape evolution models to reproduce fold growth and their associated geomorphic adjustments. Our results show that deflected rivers and inflected fold-crest elevation profile with decreasing gradient are reliable evidence of lateral fold propagation. The location of propagation is in accordance with the distribution of crest-profile slope breaks and the position where river deflection began. Then, we apply these findings to two natural examples located at the deformation fronts of the Tian Shan (NW China). Results suggest that 1) the Kashi anticline has experienced lateral propagation both westwards and eastwards; and 2) that the Yaken anticline has experienced accelerated tectonic uplift as well as eastwards propagation. These findings are supported by the constraints from geochronological dating and quantitative structural analysis. Future work that integrates folding mechanisms may provide novel insights into landscape response to complex deformation in active FTBs.

2022

1. Development of Foreland Intracratonic Plateaus (Ozark Plateau and Appalachian Plateaus): A Consequence of Topographic Inversion Due To Erosion of Adjacent Fold-Thrust Belts

   Alison M. Anders, Jingtao Lai, and Stephen Marshak

   Tectonics, 2022

   Abstract DOI

   Unlike well-known plateaus associated with Cenozoic orogens, the Appalachian and Ozark Plateaus of the eastern United States fringe the foreland side of a long inactive and deeply eroded orogen. These foreland intracratonic plateaus (FIPs), which are underlain by sub-horizontal cratonic-platform strata and, in places, foreland-basin strata, now lie 0.5–1.2 km above sea level, notably higher than adjacent fold-thrust belts. An escarpment lies at or near the boundary between the FIPs and the fold-thrust belts. Why did the topographic inversion leading to the development of the FIPs take place? To address this question, we built a numerical model, using Landlab, to simulate how topography evolves as foreland lithosphere flexes upward when post-tectonic erosion causes unloading. In this model, flat-lying cap-rock strata (sandstone and limestone) of the foreland have greater resistance to erosion than do the deformed, tilted, cleaved, and fractured strata of the fold-thrust belt, especially where the fold-thrust belt contains argillaceous facies. We tested the model by characterizing the development of the Ozark Plateau in the foreland of the Ouachita fold-thrust belt. Results demonstrate that regional isostatic uplift due to erosion, given reasonable differences in resistance to erosion between the fold-thrust belt and the foreland, can generate the observed topographic inversion and a distinct escarpment, yielding a plateau. This model may help explain the post-Paleozoic evolution of the Catskill Mountains, the Deep Valleys Province, and the Cumberland Plateau, highlands which border the Appalachian fold-thrust belt.

2021

1. Numerical Modeling of Groundwater-driven Stream Network Evolution in Low-relief Post-glacial Landscapes

   Cecilia Cullen, Alison M Anders, Jingtao Lai, and Jennifer L Druhan

   Earth Surface Processes and Landforms, 2021

   Abstract DOI

   In the low-relief post-glacial landscapes of the Central Lowlands of the United States, fluvial networks formed and expanded following deglaciation despite the low slopes and large fraction of the land surface occupied by closed depressions. Low relief topography allows for subtle surface water divides and increases the likelihood that groundwater divides do not coincide with surface water divides. We investigate how groundwater transfer across subtle surface water divides facilitates channel network expansion using a numerical model built on the Landlab platform. Our model simulates surface and subsurface water routing and fluvial erosion. We consider two end-member scenarios for surface water routing, one in which surface water in closed depressions is forced to connect to basin outlets (routing) and one in which surface water in closed depressions is lost to evapotranspiration (no routing). Groundwater is modeled as fully saturated flow within a confined aquifer. Groundwater emerges as surface water where the landscape has eroded to a specified depth. We held the total water flux constant and varied the fraction of water introduced as groundwater versus precipitation. Channel growth is significantly faster in routing cases than no-routing cases given identical groundwater fractions. In both routing and no-routing cases, channel expansion is fastest when  30% of the total water enters the system as groundwater. Groundwater contributions also produce distinctive morphology including steepened channel profiles below groundwater seeps. Groundwater head gradients evolve with topography and groundwater-fed channels can grow more quickly than channels with larger surface water catchments. We conclude that rates of channel network growth in low-relief post-glacial areas are sensitive to groundwater contributions. More broadly, our findings suggest that landscape evolution models may benefit from more detailed representation of hydrologic processes.

2. 

   Climatic Controls on Mountain Glacier Basal Thermal Regimes Dictate Spatial Patterns of Glacial Erosion

   Jingtao Lai, and Alison M Anders

   Earth Surface Dynamics, 2021

   Abstract DOI

   Climate has been viewed as a primary control on the rates and patterns of glacial erosion, yet our understanding of the mechanisms by which climate influences glacial erosion is limited. We hypothesize that climate controls the patterns of glacial erosion by altering the basal thermal regime of glaciers. The basal thermal regime is a first-order control on the spatial patterns of glacial erosion. Polythermal glaciers contain both cold-based portions that protect bedrock from erosion and warm-based portions that actively erode bedrock. In this study, we model the impact of various climatic conditions on glacier basal thermal regimes and patterns of glacial erosion in mountainous regions. We couple a sliding-dependent glacial erosion model with the Parallel Ice Sheet Model (PISM) to simulate the evolution of the glacier basal thermal regime and glacial erosion in a synthetic landscape. We find that both basal thermal regimes and glacial erosion patterns are sensitive to climatic conditions, and glacial erosion patterns follow the patterns of the basal thermal regime. Cold temperature leads to limited glacial erosion at high elevations due to cold-based conditions. Increasing precipitation can overcome the impact of cold temperature on the basal thermal regime by accumulating thick ice and lowering the melting point of ice at the base of glaciers. High precipitation rates, therefore, tend to cause warm-based conditions at high elevations, resulting in intensive erosion near the peak of the mountain range. Previous studies often assessed the impact of climate on the spatial patterns of glacial erosion by integrating climatic conditions into the equilibrium line altitudes (ELAs) of glaciers, and glacial erosion is suggested to be maximal around the ELA. However, our results show that different climatic conditions produce glaciers with similar ELAs but different patterns of basal thermal regime and glacial erosion, suggesting that there might not be any direct correlation between ELAs and glacial erosion patterns.

2020

1. 

   Tectonic Controls on Rates and Spatial Patterns of Glacial Erosion through Geothermal Heat Flux

   Jingtao Lai, and Alison M. Anders

   Earth and Planetary Science Letters, 2020

   Abstract DOI

   Glacial erosion has shaped many mountain belts during the cold periods of the Late Cenozoic. The rate of glacial erosion is sensitive to the subglacial environment, including both the subglacial hydrology and the basal thermal regime. Geothermal heat from underlying bedrock is a major contributor to glacier energy budgets, controlling ice dynamics at the ice-bed interface by changing the basal temperature and the supply of meltwater. Despite the known influence of geothermal heat on the subglacial environment, its impact on glacial erosion has received little study. The geothermal heat flux in glaciated mountain ranges varies widely as a function of the tectonic setting. Therefore, if glacial erosion is sensitive to geothermal heat flux, the evolution of glaciated landscapes may depend upon tectonically-controlled geothermal gradients. We explore the impact of geothermal heat flux on the rates and spatial patterns of glacial erosion in mountain ranges using numerical models. We couple a sliding-dependent glacial erosion model with the Parallel Ice Sheet Model (PISM) to simulate the evolution of a synthetic glacial landscape. We find a robust tendency for increasing glacial erosion with increasing geothermal heat flux. The spatial pattern of erosion also varies with the magnitude of geothermal heat flux. At low geothermal heat flux, glacial erosion is consistently focused in major valleys. As geothermal heat flux increases, the area of significant glacial erosion expands into higher elevations and the rate of erosion increases. The location of maximum erosion migrates up-valley as geothermal heat flux increases, suggesting that glacial erosion tends to produce distinct landscapes as a function of geothermal heat flux. Our finding suggests that active mountain belts with high geothermal heat flux will express the glacial buzzsaw effect, in which high elevation topography is preferentially removed by glacial erosion. Glaciers at passive margins with low geothermal heat flux, in contrast, will tend to incise deep valleys at relatively low elevations. Previous work on the interaction between tectonics and landscape evolution has focused on relief generation and fracturing of rocks. Our results introduce a novel potential linkage between tectonics and erosion based on the sensitivity of glacial erosion to geothermal heat.

2018

1. 

   Modeled Postglacial Landscape Evolution at the Southern Margin of the Laurentide Ice Sheet: Hydrological Connection of Uplands Controls the Pace and Style of Fluvial Network Expansion

   Jingtao Lai, and Alison M. Anders

   Journal of Geophysical Research: Earth Surface, 2018

   Abstract DOI

   Landscapes of the U.S. Central Lowland were repeatedly affected by the Laurentide Ice Sheet. Glacial processes diminished relief and disrupted drainage networks. Deep valleys carved by meltwater were disconnected from the surrounding uplands. The upland area lacking surface water connection to the drainage network is referred to as noncontributing area (NCA). Decreasing fractions of NCA on older surfaces suggest that NCA becomes drained over time. We propose that the integration could occur via (1) capture of NCA as channels propagate into the upland or (2) subsurface or intermittent surface connection of NCA to external drainage networks providing increased discharge to promote channel incision. We refer the two cases as “disconnected” and “connected” since the crucial difference between them is the hydrological connection of the upland to external drainage. We investigate the differences in evolution and morphology of channel networks in low-relief landscapes under disconnected and connected regimes using numerical simulations. We observe substantially faster rates of erosion and integration of the channel network in the connected case. The connected case also creates longer, more sinuous channels than the disconnected case. Sensitivity tests indicate that hillslope diffusivity has little influence on the evolution and morphology. The fluvial erosion coefficient has significant impact on the rate of evolution, and it influences the morphology to a lesser extent. Our results and a qualitative comparison with landscapes of the glaciated U.S. Central Lowland suggest that connection of NCAs is a potential control on the evolution and morphology of postglacial landscapes.

Conference abstracts

2024

1. Climate-Driven Topographic Asymmetry Enhanced by Glaciers: Implication for Divide Stability in Glacial Landscapes

   Jingtao Lai, and Kimberly Huppert

   In EGU General Assembly 2024, 2024

2023

1. Relief Evolution in Mountain Ranges Controlled by Glacier Dynamics

   Jingtao Lai, and Kimberly Huppert

   In AGU Fall Meeting 2023, 2023
2. Asymmetric glaciation, divide migration, and postglacial fluvial response times in the Qilian Shan

   Jingtao Lai, and Kimberly Huppert

   In EGU General Assembly 2023, 2023

2022

1. Cross-divide topographic contrasts created by asymmetrical glaciation: A case study from the northeastern Qilian Shan

   Jingtao Lai, and Kimberly Huppert

   In EGU General Assembly 2022, 2022

2021

1. What We Can Expect from Our Model–a Comparison of Sediment Conservation Schemes in Models of Bedrock-alluvial River Channel Evolution

   Jingtao Lai, and Kimberly Huppert

   In AGU Fall Meeting 2021, 2021
2. Climatic controls on mountain glacier basal thermal regimes dictate spatial patterns of glacial erosion

   Jingtao Lai, and Alison M Anders

   In EGU General Assembly 2021, 2021

2019

1. Tectonic controls on rates and spatial patterns of glacial erosion through geothermal heat flux

   Jingtao Lai, and Alison M Anders

   In AGU Fall Meeting 2019, 2019
2. The influence of flexural unloading and rock fractures on landscape evolution at the boundary between a cratonic platform and an orogen: A case study of uplift in the southern Ozark Plateau

   Jingtao Lai, Alison Anders, and Stephen Marshak

   In GSA Annual Meeting in Phoenix, Arizona, USA-2019, 2019

2018

1. A Comparison of Basal Sliding and Erosion in Numerical Glacial Landscape Evolution Models Using Two Different Sliding Laws

   Jingtao Lai, and Alison M Anders

   In AGU Fall Meeting 2018, 2018
2. Climatic controls on glacial erosion – insights from numerical glacial landscape evolution modeling

   Jingtao Lai, and Alison Anders

   In GSA Annual Meeting in Indianapolis, Indiana, USA-2018, 2018

Thesis

2020

1. PhD Thesis

   Constraining tectonic and climatic controls on glacial/postglacial landscape evolution using numerical modeling

   Jingtao Lai

   2020

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