Oceanography and Atmospheric Sciences and Meteorology Commons^™

Drought Monitoring And Assessment: Remote Sensing And Modeling Approaches For The Famine Early Warning Systems Network, G B. Senay, N M. Velpuri, S Bohms, M Budde, C Young, J Rowland, J P. Verdin

United States Geological Survey: Staff Publications

Drought monitoring is an essential component of drought risk management. It is usually carried out using drought indices/indicators that are continuous functions of rainfall and other hydrometeorological variables. This chapter presents a few examples of how remote sensing and hydrologic modeling techniques are being used to generate a suite of drought monitoring indicators at dekadal (10-day), monthly, seasonal, and annual time scales for several selected regions around the world. Satellite-based rainfall estimates are being used to produce drought indicators such as standardized precipitation index, dryness indicators, and start of season analysis. The Normalized Difference Vegetation Index is being used to …

On Underestimation Of Global Vulnerability To Tree Mortality And Forest Die-Off From Hotter Drought In The Anthropocene, Craig D. Allen, David D. Breshears, Nate G. Mcdowell

United States Geological Survey: Staff Publications

Patterns, mechanisms, projections, and consequences of tree mortality and associated broadscale forest die-off due to drought accompanied by warmer temperatures—‘‘hotter drought’’, an emerging characteristic of the Anthropocene—are the focus of rapidly expanding literature. Despite recent observational, experimental, and modeling studies suggesting increased vulnerability of trees to hotter drought and associated pests and pathogens, substantial debate remains among research, management and policy-making communities regarding future tree mortality risks. We summarize key mortalityrelevant findings, differentiating between those implying lesser versus greater levels of vulnerability. Evidence suggesting lesser vulnerability includes forest benefits of elevated [CO2] and increased water-use efficiency; observed and modeled increases …

Possible Tsunami Deposits On The Caribbean Coast Of The Yucatán Peninsula, Charles Shaw, Larry Benson

United States Geological Survey: Staff Publications

The western Caribbean Basin is notable for its tectonic stability. It has experienced no historical earthquakes or the tsunami that sometimes accompany them. This paper describes a single, wedge-shaped, boulder-covered, coastal berm on the Yucatán coast of México that stretches unbroken for 50 km across a coastal segment characterized by rocky headlands that alternate with crescent beaches. The remainder of the 350 km of Yucatán coast consists mostly of mangrove that extends 1 to 30 km inland, often behind long, sandy beaches. On the headlands, the surface of the berm is densely paved with boulders—large boulders on its seaward face …

Developing A 30-M Grassland Productivity Estimation Map For Central Nebraska Using 250-M Modis And 30-M Landsat-8 Observations, Yingxin Gu, Bruce K. Wylie

United States Geological Survey: Staff Publications

Accurately estimating aboveground vegetation biomass productivity is essential for local ecosystem assessment and best land management practice. Satellite-derived growing season time-integrated Normalized Difference Vegetation Index (GSN) has been used as a proxy for vegetation biomass productivity. A 250-m grassland biomass productivity map for the Greater Platte River Basin had been developed based on the relationship between Moderate Resolution Imaging Spectroradiometer (MODIS) GSN and Soil Survey Geographic (SSURGO) annual grassland productivity. However, the 250-m MODIS grassland biomass productivity map does not capture detailed ecological features (or patterns) andmay result in only generalized estimation of the regional total productivity. Developing a high …

Radiocarbon Dating Of Late Quaternary Sediments Using Fossil Gastropod Shells, Jeffrey S. Pigati, John P. Mcgeehin, Daniel R. Muhs

United States Geological Survey: Staff Publications

Terrestrial gastropods are one of the most successful groups of organisms on Earth. Their distribution includes all continents except Antarctica, and they occupy exceptionally diverse habitats, from marshes and wet meadows to alpine forests and Arctic tundra. Their shells are also commonly preserved in Quaternary deposits and potentially could be used for ¹⁴C dating. However, terrestrial gastropods are known to ingest limestone and incorporate the old carbon in their shells, resulting in apparent ages that are often too old. Recent studies have shown that many small (<1 cm diameter) terrestrial gastropods avoid this “limestone problem” even when living in areas in which carbonate rocks are readily available. However, the shells must also behave as closed systems with respect to carbon if their ages are to be considered reliable. Our latest work has been aimed at testing if small gastropod shells do, in fact, remain closed systems in late Quaternary deposits over a wide array of climate conditions across North America. Our results demonstrate that ages derived from Succineidae shells are identical to wood and charcoal ages in loess in Alaska, glacial deposits in the upper Midwest, loess in the Great Plains, and paleowetlands in the desert southwest. Moreover, Succineidae shell ages routinely fall within permitted limits set by stratigraphic boundaries, require less interpretation than humic acid ages that are commonly used in loess studies, can provide additional stratigraphic coverage to previous dating efforts, and maintain stratigraphic order more often than luminescence ages from the same stratigraphic intervals. Thus, we conclude that fossil Succineidae shells, and shells of a few other small gastropods, can be used for ¹⁴C dating regardless of the local lithology, past climate, or environmental …

Late Quaternary Sea-Level History And The Antiquity Of Mammoths (Mammuthus Exilis And Mammuthus Columbi), Channel Islands National Park, California, Usa, Daniel R. Muhs, Kathleen R. Simmons, Lindsey T. Groves, John Mcgeehin, R. Randall Schumann, Larry D. Agenbroad

United States Geological Survey: Staff Publications

Fossils of Columbian mammoths (Mammuthus columbi) and pygmymammoths (Mammuthus exilis) have been reported from Channel Islands National Park, California. Most date to the last glacial period (Marine Isotope Stage [MIS] 2), but a tusk of M. exilis (or immature M. columbi) was found in the lowest marine terrace of Santa Rosa Island. Uranium-series dating of corals yielded ages from 83.8 ± 0.6 ka to 78.6 ± 0.5 ka, correlating the terrace withMIS 5.1, a time of relatively high sea level.Mammoths likely immigrated to the islands by swimming during the glacial periodsMIS 6 (~150 ka) orMIS 8 (~250 ka),when sea levelwas …

Sea Level, Paleogeography, And Archeology On California's Northern Channel Islands, Leslie Reeder- Myers, Jon Erlandson, Daniel R. Muhs, Torben Rick

United States Geological Survey: Staff Publications

Sea-level rise during the late Pleistocene and early Holocene inundated nearshore areas in many parts of the world, producing drastic changes in local ecosystems and obscuring significant portions of the archeological record. Although global forces are at play, the effects of sea-level rise are highly localized due to variability in glacial isostatic adjustment (GIA) effects. Interpretations of coastal paleoecology and archeology require reliable estimates of ancient shorelines that account for GIA effects. Here we build on previous models for California's Northern Channel Islands, producing more accurate late Pleistocene and Holocene paleogeographic reconstructions adjusted for regional GIA variability. This region has …

Corn Belt Soil Carbon And Macronutrient Budgets With Projected Sustainable Stover Harvest, Zhengxi Tan, Shuguang Liu

United States Geological Survey: Staff Publications

Corn (Zea mays L.) stover has been identified as a prime feedstock for biofuel production in the U.S. Corn Belt because of its perceived abundance and availability, but long-term stover harvest effects on regional nutrient budgets have not been evaluated. We defined the minimum stover requirement (MSR) to maintain current soil organic carbon levels and then estimated current and future soil carbon (C), nitrogen (N), phosphorus (P), and potassium (K) budgets for various stover harvest scenarios. Analyses for 2006 through 2010 across the entire Corn Belt indicated that currently, 28 Tg or 1.6 Mgha^-1 of stover could be sustainably …

The Distribution Of Selected Elements And Minerals In Soil Of The Conterminous United States, Laurel Woodruff, William F. Cannon, David B. Smith, Federico Solano

United States Geological Survey: Staff Publications

In 2007, the U.S. Geological Survey initiated a low-density (1 site per 1600 km², 4857 sites) geochemical andmineralogical survey of soil of the conterminous United States as part of the North American Soil Geochemical Landscapes Project. Three soil samples were collected, if possible, from each site; (1) a sample from a depth of 0 to 5 cm, (2) a composite of the soil A-horizon, and (3) a deeper sample from the soil C-horizon or, if the top of the C-horizon was at a depth greater than 100 cm, from a depth of approximately 80–100 cm. The <2 mm fraction of each sample was analysed for a suite of 45 major and trace elements following near-total multi-acid digestion. The major mineralogical components in samples from the soil A- and C-horizons were determined by a quantitative X-ray diffraction method using Rietveld refinement. Sampling ended in 2010 and chemical and mineralogical analyses were completed in May 2013.Maps of the conterminous United States showing predicted element and mineral concentrations were interpolated from actual soil data for each soil sample type by an inverse distance weighted (IDW) technique using ArcGIS software. Regional- and national-scale map patterns for selected elements and minerals apparent in interpolated maps are described here in the context of soil-forming factors and possible human inputs. These patterns can be related to (1) soil parent materials, for example, in the distribution of quartz, (2) climate impacts, for example, in the distribution of feldspar and kaolinite, (3) soil age, for example, in the distribution of carbonate in young glacial deposits, and (4) possible anthropogenic loading of phosphorus (P) and lead (Pb) to surface soil. This new geochemical and mineralogical data set for the conterminous United States represents a major step forward from prior national-scale soil geochemistry data and provides a robust soil data framework for the United States now and into the future.

Toxicity Reference Values For Chlorophacinone And Their Application For Assessing Anticoagulant Rodenticide Risk To Raptors, Barnett A. Rattner, Katherine E. Horak, Rebecca S. Lazarus, Sandra L. Schultz, Susan Knowles, Benjamin G. Abbo, Steven F. Volker

United States Geological Survey: Staff Publications

Despite widespread use and benefit, there are

growing concerns regarding hazards of second-generation

anticoagulant rodenticides to non-target wildlife which

may result in expanded use of first-generation compounds,

including chlorophacinone (CPN). The toxicity of CPN

over a 7-day exposure period was investigated in American

kestrels (Falco sparverius) fed either rat tissue mechanically-

amended with CPN, tissue from rats fed Rozol bait

(biologically-incorporated CPN), or control diets (tissue

from untreated rats or commercial bird of prey diet)

ad libitum. Nominal CPN concentrations in the formulated

diets were 0.15, 0.75 and 1.5 µg/g food wet weight, and

measured concentrations averaged 94 …

Decadal Re-Evaluation Of Contaminant Exposure And Productivity Of Ospreys (Pandion Haliaetus) Nesting In Chesapeake Bay Regions Of Concern, Rebecca S. Lazarus, Barnett A. Rattner, Peter C. Mcgowan, Robert C. Hale, Sandra L. Schultz, Natalie K. Karouna-Renier, Mary Ann Ottinger

United States Geological Survey: Staff Publications

The last large-scale ecotoxicological study of ospreys (Pandion haliaetus) in Chesapeake Bay was conducted in 2000-2001 and focused on U.S. EPA-designated Regions of Concern (ROCs; Baltimore Harbor/ Patapsco, Anacostia/middle Potomac, and Elizabeth Rivers). In 2011-2012, ROCs were re-evaluated to determine spatial and temporal trends in productivity and contaminants. Concentrations of p,p'-DDE were low in eggs and below the threshold associated with eggshell thinning. Eggs from the Anacostia/ middle Potomac Rivers had lower total PCB concentrations in 2011 than in 2000; however, concentrations remained unchanged in Baltimore Harbor. Polybrominated diphenyl ether flame retardants declined by 40%, and five alternative …

A Simple Web-Based Tool To Compare Freshwater Fish Data Collected Using Afs Standard Methods, Scott A. Bonar, Norman Mercado-Silva, Matt Rahr, Yuta T. Torrey, Averill Cate Jr.

United States Geological Survey: Staff Publications

The American Fisheries Society (AFS) recently published Standard Methods for Sampling North American Freshwater Fishes. Enlisting the expertise of 284 scientists from 107 organizations throughout Canada, Mexico, and the United States, this text was developed to facilitate comparisons of fish data across regions or time. Here we describe a user-friendly web tool that automates among-sample comparisons in individual fish condition, population length-frequency distributions, and catch per unit effort (CPUE) data collected using AFS standard methods. Currently, the web tool (1) provides instantaneous summaries of almost 4,000 data sets of condition, length frequency, and CPUE of common freshwater fishes collected …

Rural Year-Round Growing To Ameliorate A Possible Negative Effect From Climate Change, Kimberlie A. Brussa

Walden Dissertations and Doctoral Studies

The Intergovernmental Panel on Climate Change (IPCC) suggested that, as the world population grows, food and water shortages will become even more serious issues (IPPC's 2014 predictions about the future effects of climate change (CC), Year-round growing (YRG) may provide a way for communities to extend growing seasons, expand local farm systems, and provide food year round. This case study included a detailed analysis of responses from representatives of all sectors of rural Mesa County, Colorado, regarding YRG and a local food and farm plan due to CC. The case was bounded by time (6 months of data collection) which …

Factors Affecting Emergency Manager, First Responder, And Citizen Disaster Preparedness, Tiffany Cooks

Walden Dissertations and Doctoral Studies

Despite the increased frequency of natural and man-made disasters, there is a problem in the level of preparedness of emergency managers, responders, and citizens to address them. The purpose of this grounded theory study was to explore the factors that affect these groups' preparedness to inform the development of better emergency plans to handle emergency incidences. The conceptual framework for the study was knowledge management, which was used with a grounded theory approach. The study was guided by primary research questions that focused on understanding psychological, material, temporal, organizational, and other factors that affect the preparedness of emergency managers, first …

Numerical Simulation Of Cold Front-Related Hydrodynamics Of Wax Lake Delta, Qian Zhang

LSU Doctoral Dissertations

This study applies a three-dimensional numerical model ECOM-si to simulate the circulation in the Wax Lake delta under winter cold front conditions. This model uses real topography and bathymetry of the area to reproduce tides and the circulation between December 2012 and January 2013, which captures a total of seven cold front passages. The model results demonstrate that the circulation in the Wax Lake delta area is significantly affected by the winter cold fronts. The major findings are: (1) Water fluxes in the delta distributary network are not solely propagated within the channels but also between the channels, indicating inundation …

Mining, Risk And Climate Resilience In The 'Other' Pacific: Latin American Lessons For The South Pacific, Anthony J. Bebbington, Jeffrey Bury, Nicholas Cuba, John Rogan

Geography

We suggest the value of considering Pacific Latin America and the South Pacific in relationship to each other in contexts of climate change and investment in extractive industry. The paper explores the interactions between extractive industry, climate change and environmental governance through the lenses of double exposure, double movements, resilience and risk. The first part of the paper addresses the nature and scope of investments in extractive industries in this 'other Pacific'. The geography of these investments is changing the actual and perceived distribution of exposure and risk in the region. The nature of this risk is also being affected …

Large Carbon Release Legacy From Bark Beetle Outbreaks Across Western United States, Bardan Ghimire, Christopher A. Williams, G. James Collatz, Melanie Vanderhoof, John Rogan, Dominik Kulakowski, Jeffrey G. Masek

Geography

Warmer conditions over the past two decades have contributed to rapid expansion of bark beetle outbreaks killing millions of trees over a large fraction of western United States (US) forests. These outbreaks reduce plant productivity by killing trees and transfer carbon from live to dead pools where carbon is slowly emitted to the atmosphere via heterotrophic respiration which subsequently feeds back to climate change. Recent studies have begun to examine the local impacts of bark beetle outbreaks in individual stands, but the full regional carbon consequences remain undocumented for the western US. In this study, we quantify the regional carbon …

Negative Feedbacks On Bark Beetle Outbreaks: Widespread And Severe Spruce Beetle Infestation Restricts Subsequent Infestation, Sarah J. Hart, Thomas T. Veblen, Nathan Mietkiewicz, Dominik Kulakowski

Geography

Understanding disturbance interactions and their ecological consequences remains a major challenge for research on the response of forests to a changing climate. When, where, and how one disturbance may alter the severity, extent, or occurrence probability of a subsequent disturbance is encapsulated by the concept of linked disturbances. Here, we evaluated 1) how climate and forest habitat variables, including disturbance history, interact to drive 2000s spruce beetle (Dendroctonus rufipennis) infestation of Engelmann spruce (Picea engelmannii) across the Southern Rocky Mountains; and 2) how previous spruce beetle infestation affects subsequent infestation across the Flat Tops Wilderness in northwestern Colorado, which experienced …

Interactions Among Spruce Beetle Disturbance, Climate Change And Forest Dynamics Captured By A Forest Landscape Model, Christian Temperli, Thomas T. Veblen, Sarah J. Hart, Dominik Kulakowski, Alan J. Tepley

Geography

The risk of bark beetle outbreaks is widely predicted to increase because of a warming climate that accelerates temperature-driven beetle population growth and drought stress that impairs host tree defenses. However, few if any studies have explicitly evaluated climatically enhanced beetle population dynamics in relation to climate-driven changes in forest composition and structure that may alter forest suitability for beetle infestation. We synthesized current understanding of the interactions among climate, spruce beetles (Dendroctonus rufipennis) and forest dynamics to parameterize and further advance the bark beetle module of a dynamic forest landscape model (LandClim) that also integrates fire and wind disturbance …

Assessing The Potential Impacts Of Declining Arctic Sea Ice Cover On The Photochemical Degradation Of Dissolved Organic Matter In The Chukchi And Beaufort Seas, Christie L. Logvinova, Karen E. Frey, Paul J. Mann, Aron Stubbins, Robert G.M. Spencer

Geography

A warming and shifting climate in the Arctic has led to significant declines in sea ice over the last several decades. Although these changes in sea ice cover are well documented, large uncertainties remain in how associated increases in solar radiation transmitted to the underlying ocean water column will impact heating, biological, and biogeochemical processes in the Arctic Ocean. In this study, six under-ice marine, two ice-free marine, and two ice-free terrestrially influenced water samples were irradiated using a solar simulator for 72 h (representing ~10 days of ambient sunlight) to investigate dissolved organic matter (DOM) dynamics from the Chukchi …

Sea-Air Co2 Exchange In The Western Arctic Coastal Ocean, Wiley Evans, Jeremy T. Mathis, Jessica N. Cross, Nicholas R. Bates, Karen E. Frey, Brent G.T. Else, Tim N. Papkyriakou, Mike D. Degrandpre, Fakhrul Islam, Wei Jun Cai, Baoshan Chen, Michiyo Yamamoto-Kawai, Eddy Carmack, William J. Williams, Taro Takahashi

Geography

The biogeochemical seascape of the western Arctic coastal ocean is in rapid transition. Changes in sea ice cover will be accompanied by alterations in sea-air carbon dioxide (CO2) exchange, of which the latter has been difficult to constrain owing to sparse temporal and spatial data sets. Previous assessments of sea-air CO2 flux have targeted specific subregional areas of the western Arctic coastal ocean. Here a holistic approach is taken to determine the net sea-air CO2 flux over this broad region. We compiled and analyzed an extensive data set of nearly 600,000 surface seawater CO2 partial pressure (pCO2) measurements spanning 2003 …

Characterization Of Tropical Clouds Using Multi-Satellite Observations, Ricardo Anderson

Dissertations and Theses

Clouds an important component of the earth-climate system and play a critical role in affecting energy and water cycle of the planet. In particular, tropical convective clouds account for the majority of the precipitation that fall on the Earth's surface. Multiple active satellite missions in recent decade such as TRMM (Tropical Rainfall Measurement Mission), and CloudSat have provided fruitful new insight into the internal structures of these tropical convective clouds. In conjunction with cloud data from ISCCP (International Satellite Cloud Climatology Project), that is based passive remote sensing technology in the visible and infrared spectrum, this allows for a more …

Intra- And Inter-Seasonal Variability Of Supra-Glacial 1 Streams And Lakes Over The West Greenland Ice Sheet 2 From High-Resolution Satellite Optical Data, Michael Gregory Brown

Dissertations and Theses

The Greenland ice sheet (GrIS) is one of the largest glacial ice masses on Earth, second only to the Antarctic ice sheet. The surface hydrology of the GrIS plays a crucial role on the surface energy and mass balance budgets of the ice sheet as a whole. Surface water, known as supra-glacial water, is seasonally found in the ablation zone and feeds the en-glacial and sub-glacial hydrological environments of the ice sheet. The spatial distribution of surface streams is poorly understood and their temporal variability is (to our knowledge) unknown. One of the reasons for the lack of knowledge on …

Propagation Of Lightning Through Thick Thunderclouds, Isaiah Henry, Dieudonné D. Phanord

McNair Poster Presentations

The phenomenon that is lightning, have sparked the interest of physicists and scientists for centuries. The journey to understanding this phenomenon of high-current electric discharge, can unlock the secret to other lightning related phenomenons. Lightning is a major source of interference in many types of radio communications. The effects of lightning on space crafts, nuclear power plants, and sophisticated military equipment, are problems of increasing concern. The purpose of this research is to study the propagation of lightning through optically thick thunderclouds by applying knowledge of cloud micro-physics, the physics of lightning, diffusion approximations, and an understanding of the scattering …

Variability Of No And No2 Above The Snowpack At Summit, Greenland, Zhixin Wang

Dissertations, Master's Theses and Master's Reports - Open

Nitric oxide (NO) and nitrogen dioxide (NO₂) were measured at levels of approximately 7.5 m, 3 m, and 0.5 m above the surface snowpack at Summit, Greenland from July 2008 to July 2010, respectively, with two sets of instrument systems. Instrument I measured NO and NO₂ at levels of 3 m and 0.5 m with two inlets, and instrument II measured NO and NO₂ at a level of 7.5 m plus total reactive nitrogen oxides (NO_y) at the same level with one inlet. Compared to previous measurements, the data provided the first year-round simultaneous …

Arctic Ocean Bathymetry: A Necessary Geospatial Framework, Martin Jakobsson, Larry A. Mayer, Dave Monahan

Center for Coastal and Ocean Mapping

Most ocean science relies on a geospatial infrastructure that is built from bathymetry data collected from ships underway, archived, and converted into maps and digital grids. Bathymetry, the depth of the seafloor, besides having vital importance to geology and navigation, is a fundamental element in studies of deep water circulation, tides, tsunami forecasting, upwelling, fishing resources, wave action, sediment transport, environmental change, and slope stability, as well as in site selection for platforms, cables, and pipelines, waste disposal, and mineral extraction. Recent developments in multibeam sonar mapping have so dramatically increased the resolution with which the seafloor can be portrayed …

Euclidean Reconstruction Of Natural Underwater Scenes Using Optic Imagery Sequence, Han Hu

Center for Coastal and Ocean Mapping

The development of maritime applications require monitoring, studying and preserving of detailed and close observation on the underwater seafloor and objects. Stereo vision offers advanced technologies to build 3D models from 2D still overlapping images in a relatively inexpensive way. However, while image stereo matching is a necessary step in 3D reconstruction procedure, even the most robust dense matching techniques are not guaranteed to work for underwater images due to the challenging aquatic environment. In this thesis, in addition to a detailed introduction and research on the key components of building 3D models from optic images, a robust modified quasi-dense …

Quantifying Florida Bay Habitat Suitability For Fishes And Invertebrates Under Climate Change Scenarios, Kelly A. Kearney, Mark J. Butler Iv, Robert Glazer, Christopner R. Kelble, Joseph E. Serafy, Erik Stabenau

Biological Sciences Faculty Publications

The Florida Bay ecosystem supports a number of economically important ecosystem services, including several recreational fisheries, which may be affected by changing salinity and temperature due toclimate change. In this paper, we use a combination of physical models and habitat suitability index models to quantify the effects of potential climate change scenarios on a variety of juvenile fish and lobster species in Florida Bay. The climate scenarios include alterations in sea level, evaporation and precipitation rates, coastal runoff, and water temperature. We find that the changes in habitat suitability vary in both magnitude and direction across the scenarios and species, …

Casitas: A Location-Dependent Ecological Trap For Juvenile Caribbean Spiny Lobsters, Panulirus Argus, Benjamin C. Gutzler, Mark J. Butler Iv, Donald C. Behringer

Biological Sciences Faculty Publications

Casitas are artificial shelters used by fishers to aggregate Caribbean spiny lobsters (Panulirus argus) for ease of capture. However, casitas may function as an ecological trap for juvenile lobsters if they are attracted to casitas and their growth or mortality is poorer compared with natural shelters. We hypothesized that juvenile lobsters may be at particular risk if attracted to casitas because they are less able than larger individuals to defend themselves, and do not forage far from shelter. We compared the nutritional condition, relative mortality, and activity of lobsters of various sizes in casitas and natural shelters in adult and …

On The Shoaling Of Solitary Waves In The Presence Of Short Random Waves, Miao Tian, Alex Sheremet, James M. Kaihatu, Gangfeng Ma

Civil & Environmental Engineering Faculty Publications

Overhead video from a small number of laboratory tests conducted by Kaihatu et al. at the Tsunami Wave Basin at Oregon State University shows that the breaking point of a shoaling solitary wave shifts to deeper water if random waves are present. The analysis of the laboratory data collected confirms that solitary waves indeed tend to break earlier in the presence of random wave field, and suggests that the effect is the result of the radiation stresses gradient induced by the random wave fields. A theoretical approach based on the forced KdV equation is shown to successfully predict the shoaling …