Oceanography and Atmospheric Sciences and Meteorology Commons^™

Biology And Ecologyof Epigean Crayfish That Inhabit Everglades Environments Procambarus Alleni (Faxon) And Procambarus Fallax (Hagen), Peggy G. Vanarman

HCNSO Student Theses and Dissertations

Two species of epigean crayfish, Procambarus alleni (the Everglades crayfish) and Procambarus fallax (slough crayfish), may be keystone species that inhabit wetlands in south Florida and the Everglades. Recent field studies showed that although these two species occur in sympatric and syntopic distribution, Everglades crayfish prefer shallow water and short hydroperiod conditions, whereas slough crayfish prefer areas that are more permanently flooded (Hendrix 2000). Slough crayfish have invaded some areas within the range occupied by Everglades crayfish, and may be the more successful competitor. Because of their critical role throughout the trophic structure of Everglades wetlands, shifts in relative abundance …

Providing The Third Dimension: High-Resolution Multibeam Sonar As A Tool For Archaeological Investigations - An Example From The D-Day Beaches Of Normandy, Larry A. Mayer, Brian R. Calder, J S. Schmidt, C Malzone

Center for Coastal and Ocean Mapping

In general, marine archaeological investigations begin in the archives, using historic maps, coast surveys, and other materials, to define submerged areas suspected to contain potentially significant historical sites. Following this research phase, a typical archaeological survey uses sidescan sonar and marine magnetometers as initial search tools. Targets are then examined through direct observation by divers, video, or photographs. Magnetometers can demonstrate the presence, absence, and relative susceptibility of ferrous objects but provide little indication of the nature of the target. Sidescan sonar can present a clear image of the overall nature of a target and its surrounding environment, but the …

Marine Information Objects (Mio) And Ecdis: Concept And Practice, Lee Alexander

Center for Coastal and Ocean Mapping

Marine Information Objects (MIOs) consist of chart- and navigation-related information that supplement the minimum information required by ECDIS to ensure safety of navigation at sea. As related to the use of Electronic Navigational Chart (ENC) data, MIOs are additional, non-mandatory information not already covered by existing IMO, IHO, or IEC standards. Such information includes ice coverage, tide/water level, current flow, meteorological, oceanographic, and marine habitats. A Harmonization Group on MIOs (HGMIO) has been established between IHO and IEC to recommend additional data and display specifications that may be incorporated into future editions of IHO and IEC standards. This paper discusses …

Electronic Chart Of The Future: The Hampton Roads Project, Rick Brennan, Colin Ware, Lee Alexander, Andy Armstrong, Larry A. Mayer, Lloyd C. Huff, Brian R. Calder, Shep M. Smith Lt, Matthew D. Plumlee, Roland J. Arsenault, Gerd Glang

Center for Coastal and Ocean Mapping

ECDIS is evolving from a two-dimensional static display of chart-related data to a decision support system capable of providing real-time or forecast information. While there may not be consensus on how this will occur, it is clear that to do this, ENC data and the shipboard display environment must incorporate both depth and time in an intuitively understandable way. Currently, we have the ability to conduct high-density hydrographic surveys capable of producing ENCs with decimeter contour intervals or depth areas. Yet, our existing systems and specifications do not provide for a full utilization of this capability. Ideally, a mariner should …

Fusing Information In A 3d Chart-Of-The-Future Display, Roland J. Arsenault, Shep M. Smith Lt, Colin Ware, Larry A. Mayer, Matthew D. Plumlee

Center for Coastal and Ocean Mapping

The Data Visualization Research Lab at the Center for Coastal and Ocean Mapping is investigating how three-dimensional navigational displays can most effectively be constructed. This effort is progressing along multiple paths and is implemented in the GeoNav3D system, a 3D chart-of-the-future research prototype. We present two lines of investigation here. First, we explore how tide, depth, and planning information can be combined (fused) into a single view, in order to give the user a more realistic picture of effective water depths. In the GeoNav3D system, 3D shaded bathymetry, coded for color depth, is used to display navigable areas. As in …

Evaluation Of The Mountain Wave Forecast Model's Stratospheric Turbulence Simulations, Mark S. Allen

Theses and Dissertations

Stratospheric turbulence (Stratoturb) is a well-known hazard to aircraft in flight. Forecasting mountain waves, specifically the breaking of these waves, is necessary to accurately predict the presence of Stratoturb. The Air Force Weather Agency (AFWA) requested a product with the capability of forecasting Stratoturb at 30, 50, and 70 mb using model data currently available, To facilitate their request, the Mountain Wave Forecast Model (MWFM) was acquired from the Naval Research Laboratory. MWFM turbulence forecasts generated twice daily over East Asia, using the AVN and MM5 models for initialization, were compared to S' layer turbulence analyses from the Rawinsonde Observation …

Comparison Of The Refractive Index Structure Constant Derived From Numerical Weather Prediction (Nwp) Models And Thermosonde Data, De Leon C. Narcisse

Theses and Dissertations

An accurate depiction of atmospheric turbulence is required for successful employment of a viable airborne laser for the Department of Defense (DOD). The ABL Special Program Office (SEC) which is tasked by the Missile Defense Agency (MDA) bas not designated any particular numerical weather model that is tasked exclusively to model optical turbulence This research compares CLEAR1, 2 X CLEAR I and thermosonde derived values of the refractive index structure constant to optical turbulence values derived from several numerical weather prediction models currently in use by the DOD. The models used were the fifth Generation Mesoscale Model (MM5), the Coupled …

Forecasting Excessive Rainfall And Low-Cloud Bases East Of The Northern Andes And Mesoscale Convective Complex Movement In Central South America, Marc R. Gasbarro

Theses and Dissertations

This research produces better forecast tools for SOUTHCOM's 25th Operational Weather Squadron (OWS) over multiple areas of operation in South America. Heavy rainfall and low-cloud base events along the northeastern Andes foothills are examined, as well as, mesoscale convective complexes (MCCs) in Central South America (CSA). Low clouds, fog, and flooding rains hamper daily Department of Defense (DoD) counter-drug operations in Northwestern South America (NWSA). In addition, fierce MCCs interfere with joint-military exercises in CSA.

Data Mining Atmospheric/Oceanic Parameters In The Design Of A Long-Range Nephelometric Forecast Tool, Richard F. Benz

Theses and Dissertations

The Department of Defense calls for long-range forecasts to aid in the planning of operations. The goal of this research was to explore the feasibility of predicting, one month in advance, the total monthly cloud cover over the country of Afghanistan. In an attempt to reach this goal, the following objectives were achieved: (1) climatological synoptic study of Afghanistan; (2) survey of Real Time Nephanalysis, outgoing longwave radiation (OLR), and surface observational data; (3) examination of teleconnection indices and sea surface temperatures; (4) standard statistical analysis for prediction; and (5) classification tree analysis (CART), In addition, due to current world …

Future Climate Analysis -- 10,000 Years To 1,000,000 Years After Present, Saxon E. Sharpe, Dwight Hoxie, Amy J. Smiecinski

Publications (YM)

The purpose of this report is to provide quantified estimates of temperature and precipitation and estimate the timing of climate states in the Yucca Mountain, Nevada, area for the period from 10,000 to 1,000,000 years beyond the present. Primary tasks are limited to: 1) selecting modern analog climate stations for three different magnitude glacial stages; and, 2) determining the timing of future climate states using orbital parameter data and Devils Hole and Owens Lake records. These estimates are intended to be used as input to models of the infiltration process to assess the performance of the natural and engineered systems …

An Analysis Of The Oregon Coastal Exchange Requirement, Jordan Vinograd

Center for Lakes and Reservoirs Publications and Presentations

This report was generated at the request of the Oregon Ballast Water Task Force to address the issue of coastal shipping and exchange requirements along the West Coast of North America. The Oregon Ballast Water Management Program was established by SB 895 during the 2001 legislative session to address the introduction of aquatic nuisance species when ballast water is discharged from ships. There are several levels of ballast water management as established by the National Invasive Species Act of 1996. However, the national program does not address the issues of interstate vessel voyages. Therefore, California, Washington and Oregon have establishedm …

Effect Of Sulfate Aerosol On Tropospheric Nox And Ozone Budgets: Model Simulations And Topse Evidence, Xuexi Tie, L K. Emmons, Larry Horowitz, Guy Brasseur, Brian Ridley, Elliot Atlas, Craig Stround, Peter Hess, Andrzej Klonecki, Sasha Madronich, R. Talbot, Jack E. Dibb

Earth Sciences

The distributions of NO_x and O₃ are analyzed during TOPSE (Tropospheric Ozone Production about the Spring Equinox). In this study these data are compared with the calculations of a global chemical/transport model (Model for OZone And Related chemical Tracers (MOZART)). Specifically, the effect that hydrolysis of N₂O₅ on sulfate aerosols has on tropospheric NO_x and O₃ budgets is studied. The results show that without this heterogeneous reaction, the model significantly overestimates NO_x concentrations at high latitudes of the Northern Hemisphere (NH) in winter and spring in comparison to the observations during TOPSE; …

Seasonal Distributions Of Fine Aerosol Sulfate In The North American Arctic Basin During Topse, Eric Scheuer, R. Talbot, Jack E. Dibb, Garry Seid, Linsey J. Debell, Barry Lefer

Earth Sciences

We used the mist chamber/ion chromatography technique to quantify fine aerosol SO₄⁼(<2.7 μm) in the Arctic during the Tropospheric Ozone Production about the Spring Equinox Experiment (TOPSE) with about 2.5 min time resolution. Our effective sample area ranged from 50° to 86°N and 53° to 100°W. The seasonal evolution of fine aerosol sulfate in the Arctic troposphere during TOPSE was consistent with the phenomenon of Arctic haze. Arctic haze has been attributed to pollution from sources in the Arctic and pollution transported meridionally along stable isentropes into the Arctic in geographically broad but vertically narrow bands. These layers became more prevalent at higher altitudes as the season progressed toward summer, and the relevant isentropes are not held so close to the surface. Mean fine particle SO₄⁼ mixing ratios during TOPSE in February below 1000 m were elevated (112 pptv) and highly variable (between 28 and 290 pptv) but were significantly lower at higher altitudes (about 40 pptv). As the season progressed, elevated mixing ratios and higher variability were observed at higher altitudes, up to 7 km. In May, mixing ratios at the lowest altitudes declined but still remained higher than in February at all altitudes. The high variability in our measurements likely reflects the vertical heterogeneity of the wintertime …

An Estimate Of The Stratospheric Contribution To Springtime Tropospheric Ozone Maxima Using Topse Measurements And Beryllium-7 Simulations, Dale J. Allen, Jack E. Dibb, Brian Ridley, Kenneth E. Pickering, R. Talbot

Earth Sciences

Measurements of tropospheric ozone (O₃) between 30°N and 70°N show springtime maxima at remote locations. The contribution of seasonal changes in stratosphere–troposphere exchange (STE) to these maxima was investigated using measurements from the Tropospheric Ozone Production about the Spring Equinox Experiment (TOPSE) campaign and the beryllium-7 (⁷Be) distribution from a calculation driven by fields from the Goddard Earth Observing System Data Assimilation System (GEOS DAS). Comparison with TOPSE measurements revealed that upper tropospheric model-calculated ⁷Be mixing ratios were reasonable (a change from previous calculations) but that lower tropospheric mixing ratios were too low most likely …

Coupled Evolution Of Brox-Clox-Hox-Nox Chemistry During Bromine-Catalyzed Ozone Depletion Events In The Arctic Boundary Layer, M J. Evans, D J. Jacob, E L. Atlas, C A. Cantrell, Fred Eisele, F Flocke, A Fried, R L. Mauldin, Brian Ridley, B Wert, R. Talbot, D R. Blake, B J. Heikes, J Snow, J Walega, Andrew Weinheimer, Jack E. Dibb

Earth Sciences

Extensive chemical characterization of ozone (O₃) depletion events in the Arctic boundary layer during the TOPSE aircraft mission in March–May 2000 enables analysis of the coupled chemical evolution of bromine (BrO_x), chlorine (ClO_x), hydrogen oxide (HO_x) and nitrogen oxide (NO_x) radicals during these events. We project the TOPSE observations onto an O₃ chemical coordinate to construct a chronology of radical chemistry during O₃ depletion events, and we compare this chronology to results from a photochemical model simulation. Comparison of observed trends in ethyne (oxidized by Br) and ethane …

Stratospheric Influence On The Northern North American Free Troposphere During Topse: 7be As A Stratospheric Tracer, Jack E. Dibb, R. Talbot, Eric Scheuer, Garry Seid, Linsey J. Debell, Barry Lefer, Brian Ridley

Earth Sciences

We use ⁷Be, with HNO₃ and O₃, to identify air masses sampled from the NCAR C-130 during TOPSE that retained clear evidence of stratospheric influence. A total of 43 such air masses, spread fairly evenly across the February to May sampling period, and 40°N–86°N latitude range, were encountered. South of 55°N, nearly all clear stratospheric influence was restricted to altitudes above 6 km. At higher latitudes stratospherically influenced air masses were encountered as low as 2 km. Approximately 12% of all TOPSE sampling time at altitudes above 2 km was spent in stratospherically impacted air, above …

Ozone Depletion Events Observed In The High Latitude Surface Layer During The Topse Aircraft Program, Brian Ridley, Elliot Atlas, D Montzka, Edward V. Browell, C A. Cantrell, D R. Blake, N J. Blake, L Cinquini, Michael T. Coffey, L K. Emmons, Ronald C. Cohen, Russell J. Deyoung, Jack E. Dibb, Fred Eisele, F Flocke, A Fried, F E. Grahek, William B. Grant, Jonathan Hair, James W. Hannigan, B J. Heikes, Barry Lefer, R L. Mauldin, Jennie Moody, R E. Shetter, J Snow, R. Talbot, J A. Thornton, J Walega, Andrew Weinheimer, B Wert, Anthony Wimmers

Earth Sciences

During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) aircraft program, ozone depletion events (ODEs) in the high latitude surface layer were investigated using lidar and in situ instruments. Flight legs of 100 km or longer distance were flown 32 times at 30 m altitude over a variety of regions north of 58° between early February and late May 2000. ODEs were found on each flight over the Arctic Ocean but their occurrence was rare at more southern latitudes. However, large area events with depletion to over 2 km altitude in one case were found as far south as …

Investigations Into Free Tropospheric New Particle Formation In The Central Canadian Arctic During The Winter/Spring Transition As Part Of Topse, R J. Weber, D A. Orsini, B Wang, Eric Scheuer, R. Talbot, Jack E. Dibb, Garry Seid, Linsey J. Debell, R L. Mauldin, E Kosciuch, C A. Cantrell, Fred Eisele

Earth Sciences

In this paper, we investigate the role of in situ new particle production in the central Canadian sub-Arctic and Arctic as part of the TOPSE experiment. Airborne measurements conducted primarily in the free troposphere were made from 50° to 90°W longitude and 60° to 85°N latitude during the period from February to May 2000. Data pertinent to this paper include 3–4 nm diameter (Dp) particles, ultrafine condensation nuclei (Dp > 3 nm), fine particles (0.2 < Dp < 3 μm), and the possible nucleation precursor, sulfuric acid, and its precursor, sulfur dioxide. For data averaged over this period, most species showed little evidence for a latitudinal trend. Fine aerosol number concentrations, however, showed a slight increase with latitude. The evolution of various species concentrations over the period of the study show that fine particles also had a consistent temporal trend, increasing at all altitudes from February to May, whereas sulfur dioxide at the surface tended to peak in late March. Ultrafine condensation nuclei and 3–4 nm particles showed no temporal trends. Little evidence for in situ new particle production was observed during the study, except for one atypical event where SO₂concentrations were 3.5 ppbv, 2 orders of magnitude higher than typical levels. This paper cannot address the question of whether the observed condensation nuclei were …

Steady State Free Radical Budgets And Ozone Photochemistry During Topse, C A. Cantrell, Lee Mauldin, M Zondlo, Fred Eisele, E Kosciuch, R E. Shetter, Barry Lefer, S R. Hall, T L. Campos, Brian Ridley, J Walega, A Fried, B Wert, F Flocke, Andrew Weinheimer, James W. Hannigan, Michael T. Coffey, Elliot Atlas, S Stephens, B J. Heikes, J Snow, D R. Blake, N J. Blake, A Katzenstein, J Lopez, Edward V. Browell, Jack E. Dibb, Eric Scheuer, Garry Seid, R. Talbot

Earth Sciences

A steady state model, constrained by a number of measured quantities, was used to derive peroxy radical levels for the conditions of the Tropospheric Ozone Production about the Spring Equinox (TOPSE) campaign. The analysis is made using data collected aboard the NCAR/NSF C-130 aircraft from February through May 2000 at latitudes from 40° to 85°N, and at altitudes from the surface to 7.6 km. HO₂ + RO₂ radical concentrations were measured during the experiment, which are compared with model results over the domain of the study showing good agreement on the average. Average measurement/model ratios are 1.04 (σ …

Springtime Photochemistry At Northern Mid And High Latitudes, Yuhang Wang, Brian Ridley, A Fried, C A. Cantrell, D D. Davis, Gao Chen, J Snow, B J. Heikes, R. Talbot, Jack E. Dibb, F Flocke, Andrew Weinheimer, N J. Blake, D R. Blake, R E. Shetter, Barry Lefer, Elliot Atlas, Michael T. Coffey, J Walega, B Wert

Earth Sciences

Physical and chemical properties of the atmosphere at 0–8 km were measured during the Tropospheric Ozone Production about the Spring Equinox (TOPSE) experiments from February to May 2000 at mid (40°–60°N) and high latitudes (60°–80°N). The observations were analyzed using a diel steady state box model to examine HO_x and O₃ photochemistry during the spring transition period. The radical chemistry is driven primarily by photolysis of O₃ and the subsequent reaction of O(¹D) and H₂O, the rate of which increases rapidly during spring. Unlike in other tropospheric experiments, observed H₂O_{2 …}

Tunable Diode Laser Measurements Of Formaldehyde During The Topse 2000 Study: Distributions, Trends, And Model Comparisons, A Fried, Yuhang Wang, C A. Cantrell, B Wert, J Walega, Brian Ridley, Elliot Atlas, R E. Shetter, Barry Lefer, Michael T. Coffey, James W. Hannigan, D R. Blake, N J. Blake, Simone Meinardi, R. Talbot, Jack E. Dibb, Eric Scheuer, Oliver Wingenter, J Snow, B J. Heikes, Dieter Ehhalt

Earth Sciences

Airborne measurements of formaldehyde (CH₂O) were acquired employing tunable diode laser absorption spectroscopy (TDLAS) during the 2000 Tropospheric Ozone Production About the Spring Equinox (TOPSE) study. This study consisted of seven deployments spanning the time period from 4 February to 23 May 2000 and covered a wide latitudinal band from 40°N to 85°N. The median measured CH₂O concentrations, with a few exceptions, did not show any clear temporal trends from February to May in each of five altitude and three latitude bins examined. Detailed measurement–model comparisons were carried out using a variety of approaches employing two …

Hyperspectral Remote Sensing Protocol Development For Submerged Aquatic Vegetation In Shallow Waters, Charles R. Bostater Jr., T. Ghir, L. Bassetti, Carlton Hall, E. Reyier, R. Lowers, K. Holloway-Adkins, Robert Virnstein

Ocean Engineering and Marine Sciences Faculty Publications

Submerged aquatic vegetation (SAV) is an important indicator of freshwater and marine water quality in almost all shallow water aquatic environments. Throughout the world the diversity of submerged aquatic vegetation appears to be in decline, although sufficient historical data, of sufficient quantitative quality is lacking. Hyperspectral remote sensing technology, available from low altitude aircraft sensors, may provide a basis to improve upon existing photographic regional assessments and monitoring concerned with the aerial extent and coverage of SAV. In addition, modern low altitude remote sensing may also help in the development of environmental satellite requirements for future satellite payloads. This paper …

Optically Stimulated Luminescence Dating Supports Central Arctic Ocean Cm-Scale Sedimentation Rates, Martin Jakobsson, Jan Backman, Andrew Murray, Reidar Lovlie

Center for Coastal and Ocean Mapping

This paper presents new results from Optically Stimulated Luminescence (OSL) dating on a sediment core raised from the crest of the Lomonosov Ridge in the central Arctic Ocean. There has been much debate about dating sediment cores from the central Arctic Ocean and by using an independent absolute dating technique we aim to test whether or not relatively fast, cm-scale/ka, sedimentation rates were typical of Arctic’s Pleistocene depositional mode. On the basis of mainly paleomagnetic reversal stratigraphy, many previous studies suggest mm-scale/ka sedimentation rates. A common feature in these studies is that the first down core paleomagnetic negative inclination is …

Climatic Influences On Riverine Nitrate Flux: Implications For Coastal Marine Eutrophication And Hypoxia, Dubravko Justic, R. Eugene Turner, Nancy N. Rabalais

Faculty Publications

The average nitrate flux of the lower Mississippi River increased 3.3-fold between 1954–1967 and 1983–2000. During the same time period, the average nitrate concentration increased 2.3-fold while the average discharge increased 40%. Partitioning of the observed trend in nitrate flux among the two flux components, nitrate concentration and discharge, revealed that about 80% of the observed increase in flux could be explained by the increase in nitrate concentration. This indicates that a historical increase in the anthropogenic nutrient inputs has had a far greater impact on the lower Mississippi River nitrate flux than a change in climate. The influence of …

Habitat Utilization By Bottlenose Dolphins (Tursiops Truncatus) In Biscayne Bay, Florida, Christine A. Hudak

HCNSO Student Theses and Dissertations

Bottlenose dolphins (Tursiops truncatus) exhibit variable distribution patterns, depending upon their geographic location. Habitat utilization patterns in Biscayne Bay, Florida, were examined using the Biscayne Bay Bottlenose Dolphin Photo-ID database obtained from the National Oceanic and Atmospheric Administration (NOAA) Southeast Fisheries Science Center (SEFSC) Miami Laboratory. Habitat coverages in Biscayne Bay were obtained from the Atlas of Marine Resources Version 1.3B CD and the Biscayne Bay National Park CD. Dolphin sightings were overlaid on the habitat coverages using GIS Arcview software.

The effects of habitat, season, behavior, zone (sectioned area of Biscayne Bay), and depth on patterns …

The Grounding Of An Ice Shelf In The Central Arctic Ocean: A Modeling Experiment, Martin Jakobsson, M Siegert, Mark Paton

Center for Coastal and Ocean Mapping

A numerical ice sheet model was used in a first test towards evaluating the hypothesis that, during a period of large-scale glaciation, an ice shelf emanating from the Barents/Kara Seas grounded across parts of the Lomonosov Ridge to a depth of around 1000 m below present sea level (Jakobsson, 1999; Polyak et al., 2001). Despite that we not include complex ice shelf physics or grounding line mechanics in our model and treat the process of marine melting in a simple manner, our experiments are the necessary first steps toward providing a comprehensive reconstruction of the former ice-sheet/ice-shelf system in the …

Seafloor Segmentation Based On Bathymetric Measurements From Multibeam Echosounders Data, Yuri Rzhanov, Randy G. Cutter Jr., Larry A. Mayer

Center for Coastal and Ocean Mapping

Bathymetric data depicts the geomorphology of the seabottom and allows characterization of spatial distributions of apparent benthic habitats. The variability of seafloor topography can be defined as a texture. This prompts for the application of well developed image processing techniques for automatic delineation of regions with clucially different physiographic characteristics. In the present paper histograms of biologically motivated invariant image attributes are used for characterization of local geomorphological feahires. This technique can be naturally applied in a range of spatial scales. Local feature vectors are then submitted to a procedure which divides the set into a number of clusters each …

Evaluation Of Sampling Strategies On Load Estimation For Illinois River At Highway 59, T. S. Soerens, M. A. Nelson

Arkansas Water Resources Center Technical Reports

This study investigated the precision and accuracy of the two load calculation techniques. The study compared total phosphorus loads calculated by integration of Arkansas Water Resources Center (AWRC) intensive sampling data to loads calculated by a regression technique (rating curve) using fewer data. The 1998 AWRC dataset from the Illinois River at Arkansas Highway 59 was sub-sampled in a manner to simulate fixed period monitoring schemes supplemented with storm sampling. The ESTIMATOR software program was used to calculate loads. These loads were compared to the integrated load. The error of the integrated load when the variation in concentration between samples …

Charting Neptune's Realm: From Classical Mythology To Satellite Imagery, Osher Map Library And Smith Center For Cartographic Education

Osher Map Library Exhibition Catalogs

Charting Neptune's Realm: From Classical Mythology to Satellite Imagery.

April 4, 2000 to January 11, 2001

The charts in this exhibition explore how mariners have distinguished one piece of water from any other, by determining what phenomena can be delineated across the vast, trackless ocean and by developing notations to express those phenomena.

Mid-Holocene Climates Of The Americas: A Dynamical Response To Changed Seasonality, S. P. Harrison, J. E. Kutzbach, Z. Liu, P. J. Bartlein, B. Otto-Bliesner, Daniel R. Muhs, I. C. Prentice, R. S. Thompson

United States Geological Survey: Staff Publications

Abstract Simulations of the climatic response to mid- Holocene (6 ka BP) orbital forcing with two coupled ocean–atmosphere models (FOAM and CSM) show enhancement of monsoonal precipitation in parts of the American Southwest, Central America and northernmost South America during Northern Hemisphere summer. The enhanced onshore flow that brings precipitation into Central America is caused by a northward displacement of the inter-tropical convergence zone, driven by cooling of the equatorial and warming of the northern subtropical and mid-latitude ocean. Ocean feedbacks also enhance precipitation over the American Southwest, although the increase in monsoon precipitation there is largely driven by increases …