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    Inferring Mars' Surface Winds by Analyzing the Global Distribution of Barchan Dunes using a Convolutional Neural Network

    Date:
    29
    Tuesday
    June
    2021
    Lecture / Seminar
    Time: 10:00-11:00
    Location: https://weizmann.zoom.us/j/7621438333?pwd=c0lpdlQzYSthellXWG9rZnM0ZDRFZz09
    Lecturer: Lior Rubanenko
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Sand seas on Mars are riddled with eolian landforms created by accumulating sand ... Read more Sand seas on Mars are riddled with eolian landforms created by accumulating sand particles. When the sand supply is limited and the wind is approximately unidirectional, these landforms take the shape of crescentic barchan dunes, whose slip-faces are approximately perpendicular to the dominant wind direction, and their horns are oriented downwind. The morphology of barchan dunes is thus routinely used to infer wind conditions on Mars by manually analyzing aerial or satellite imagery. Despite the effectiveness of this technique on a local scale, employing it on a global scale remained challenging thusfar - as manually outlining individual dunes globally is impractical, and automatic detection methods have been largely ineffective at accurately segmenting dunes in images. Here we use Mask R-CNN, an instance segmentation convolutional neural network, to detect and outline dunes globally on Mars in images obtained by the Mars Reconnaissance Orbiter Context Camera (MRO CTX). We measure the morphometrics of dunes from their detected outlines, and infer the direction of the winds that formed them. By comparing the global wind distribution we derived to a global climate model, we study Mars' past and recent climate, and constrain global sand mobility thresholds which offer insight into the erosion and dust lifting capabilities of the atmosphere of the Red Planet.
    Close abstract

    The assembly of microbial communities in the ocean, one drop at a time

    Date:
    25
    Tuesday
    May
    2021
    Lecture / Seminar
    Time: 15:00-16:00
    Title: Guest Seminar via Zoom - Special time!
    Location: https://weizmann.zoom.us/j/94920680518?pwd=MDhOVUZsQWRaMGZSYndIME5lZGtRdz09Password151190
    Lecturer: Prof. Otto X. Cordero
    Organizer: Department of Plant and Environmental Sciences
    Details: Host: Dr. Assaf Gal

    Stir and mix: studying upper ocean dynamics from theory to application

    Date:
    18
    Tuesday
    May
    2021
    Lecture / Seminar
    Time: 15:00-16:00
    Location: https://weizmann.zoom.us/j/7621438333?pwd=c0lpdlQzYSthellXWG9rZnM0ZDRFZz09
    Lecturer: Abigail Bodner
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Near the ocean surface, mixing and turbulence modulate the transfer of heat, mom ... Read more Near the ocean surface, mixing and turbulence modulate the transfer of heat, momentum, carbon and other properties, between the atmosphere and ocean interior. Accurate representation of these processes in General Circulation Models (GCMs) is crucial for simulating atmosphere-ocean interactions. However, all of these processes, generally known as boundary layer turbulence and submesoscale mixing, are on scales smaller than the grid used in GCMs, even at the highest possible resolution. Current submesoscale parameterizations represent the bulk of mixing developed across submesoscale fronts– the sharp interface between waters of different densities– but it has been shown to be too simplistic and unfitting in many circumstances. The presence of turbulence has been missing from these dynamics, and in this talk I will discuss the long-lasting problem of how to correctly include them. 
Building toward a more complete understanding of these processes, a theoretical approach of perturbation analysis is used to include the effects of turbulence as a correction to classic frontogenesis (frontal sharpening) theory. This approach is next extended into a more realistic environment, using a suite of high resolution, turbulence resolving, numerical simulations. It is found that a variety of turbulent processes resulting from winds, waves, convection, and instabilities affect the formation of fronts. Furthermore, this analysis exposes severe limitations in existing techniques to predict potential vorticity dynamics in highly turbulent regimes. Lastly, I will discuss modifying the submesoscale parameterization in GCMs to represent the complex interactions with boundary layer turbulence.
    Close abstract

    What causes the leakiness of the North Atlantic Deep Western Boundary Current?

    Date:
    04
    Tuesday
    May
    2021
    Lecture / Seminar
    Time: 10:00
    Location: https://weizmann.zoom.us/j/7621438333?pwd=c0lpdlQzYSthellXWG9rZnM0ZDRFZz09
    Lecturer: Aviv Solodoch
    Organizer: Department of Earth and Planetary Sciences
    Abstract: The Atlantic Meridional Overturning Circulation (AMOC) is a circulation pattern ... Read more The Atlantic Meridional Overturning Circulation (AMOC) is a circulation pattern of great climatic importance. Its northward heat flux at the upper water column moderates European winter climate, and its descending branch captures atmospheric CO2 into the deep ocean, hence buffering the anthropogenically induced rise in global temperature. The Deep Western Boundary Current (DWBC) has classically been considered to be the main AMOC conduit southward at depth. However, tracer data have shown in recent decades that the DWBC "leaks" most of its material to the ocean interior in a small region of the North Atlantic, and that this leaked material continues southward in different, complex routes. These pathways and their causes are still little-explored and not well understood. In this talk I will present analysis of the DWBC leakiness properties and dynamics, based on existing datasets of passively drifting floats, a new high resolution regional numerical model, and theoretical analysis. Several alternative mechanisms of leakiness are considered, and a novel finding is that a leading cause for the leakiness is inertial separation of the current from the seafloor, near underwater capes. The role of eddies and their interaction with the separation process is investigated as well. Implications for the robustness of the deep AMOC pathways are discussed.
    Close abstract

    Physics-guided machine-learning parameterizations of subgrid processes for climate modeling

    Date:
    26
    Monday
    April
    2021
    Lecture / Seminar
    Time: 14:00
    Location: https://weizmann.zoom.us/j/7621438333?pwd=c0lpdlQzYSthellXWG9rZnM0ZDRFZz09
    Lecturer: Janni Yuval
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Global climate models represent small-scale processes, such as clouds and convec ... Read more Global climate models represent small-scale processes, such as clouds and convection, using subgrid models known as parameterizations. Traditional parameterizations are usually based on simplified physical models, and inaccuracies in these parameterizations are a main cause for the large uncertainty in climate projections. One alternative to traditional parameterizations is to use machine learning to learn new parameterizations which are data driven. However, machine-learning parameterizations might violate physical principles and often lead to instabilities when coupled to an atmospheric model. I will show how machine learning algorithms, such as neural networks and random forests, can be used to learn new parameterizations from the output of a three-dimensional high-resolution atmospheric model, while obeying physical constraints such as energy conservation. Implementing these parameterizations in the atmospheric model at coarse resolution leads to stable simulations that replicate the climate of the high-resolution simulation, and capture important statistics such as precipitation extremes. I will also discuss how machine-learning parameterizations can give further insights into the parameterization problem. Specifically, I will show that failures of machine-learning parameterizations can be used to better understand the relationship between large-scale fields and subgrid processes.
    Close abstract

    Advances of remote sensing in agriculture and forestry for climate change adaptation

    Date:
    06
    Tuesday
    April
    2021
    Lecture / Seminar
    Time: 00:00
    Lecturer: Tarin Paz-Kagan
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Forests and agricultural orchards are becoming increasingly susceptible to droug ... Read more Forests and agricultural orchards are becoming increasingly susceptible to drought, ‎insect ‎‎outbreaks, and disease due to climate change worldwide. Thus, forest ‎and ‎agricultural systems management needs to be proactively targeted to improve their ‎resilience to anthropogenic and ‎climate change. The potential of remote sensing ‎data for ‎agriculture and forestry has long been recognized. The global coverage and repositories of different ‎types ‎of satellite data extending integrating with developing UAVs and ‎sensor ‎capabilities provide a unique database, which allows us to develop, test, and ‎implement ‎innovative measures to adapt agriculture and forest to the foreseen climate ‎scenarios. ‎However, there is still a considerable gap between data and information. ‎Remote sensing ‎applications integrated with innovative artificial intelligence techniques ‎could make ‎fundamental discoveries for sustainable environmental management. Thus, ‎the seminar ‎aims to present advanced remote-sensing applications for agriculture and ‎forest to climate ‎change adaptation. Four case studies will be presented, including (1) ‎mapping woody ‎species distribution and richness along the climatic gradient; (2) ‎developing canopy ‎geometry traits to characterize and monitor tree structure using LiDAR ‎applications; and (3) ‎Incorporation winter tree physiology in deciduous orchard into ‎forecast- models of bloom ‎and yield, and (4) leaf to landscape approach to study ‎forest responses to drought.
    Close abstract

    Radiocarbon and geochemical investigation of corals from the northern Indian Ocean

    Date:
    04
    Thursday
    March
    2021
    Lecture / Seminar
    Time: 11:30
    Location: https://weizmann.zoom.us/j/6168548886 Passcode: 976012
    Lecturer: Dr. Harsh Raj

    Adventures in the Critical Zone: from carbon fluxes to wildfires

    Date:
    02
    Tuesday
    February
    2021
    Lecture / Seminar
    Time: 10:00
    Location: https://weizmann.zoom.us/j/7621438333?pwd=c0lpdlQzYSthellXWG9rZnM0ZDRFZz09
    Lecturer: Antonello Provenzale
    Organizer: Department of Earth and Planetary Sciences
    Abstract: The Hadley circulation is a key element of the climate system. It is traditional ... Read more The Hadley circulation is a key element of the climate system. It is traditionally defined as the zonally averaged meridional circulation in the tropics, therefore treated as a zonally symmetric phenomenon. However, differences in temperature between land and sea cause zonal asymmetries on Earth, dramatically affecting the circulation. This longitudinal dependence of the meridional circulation evokes questions about where and when the actual large scale tropical circulation occurs. Here, we look into the connection between the longitudinally dependent meridional circulation, and the actual large scale transport of air in the tropics using a coupled Eulerian and Lagrangian approach. Decomposing the velocity field into rotational and divergent components, we identify how each component affects the actual circulation. We propose an alternative definition for the circulation, that describes the actual path of air parcels in the tropics, as a tropical atmospheric conveyor belt. We further investigate this definition, analyzing the circulation under climate change and its effect on precipitation changes. We show that in order to predict future climate, the regionality and three-dimensionality of the large-scale tropical circulation must be taken into account. We find that the changes in the circulation vary significantly over longitude, and are overlooked when analyzing the zonally averaged meridional circulation. The circulation is strengthening and expanding in the center of the Pacific, a region where the circulation barely existed in past. On the other hand, the circulation is weakening in the Indo-Pacific region, where it was the most significant in the past. These differences appear as a shift in the region of ascent of the conveyor belt, that is revealed when analyzing the decomposed vertical wind. The pattern of weakening of the ascent in the Indo-Pacific and strengthening in the center of the Pacific explains the projected changes in precipitation. The Indo-Pacific region is drying, while the precipitation in the center of the Pacific is intensifying.
    Close abstract

    Viral impacts in the marine world: from single-cells to planktonic ecosystems

    Date:
    26
    Tuesday
    January
    2021
    Lecture / Seminar
    Time: 11:30-12:30
    Title: Dept. Seminar via Zoom
    Location: https://weizmann.zoom.us/j/92760289710?pwd=SEROejJMWUtBQU5PMGZ5Ri9Ud0hNZz09 Password: 740144
    Lecturer: Dr. Flora Vincent
    Organizer: Department of Plant and Environmental Sciences
    Details: Host: Prof. Assaf Vardi

    Marine electrical imaging reveals novel freshwater transport mechanism in Hawaiʻi

    Date:
    26
    Tuesday
    January
    2021
    Lecture / Seminar
    Time: 11:00
    Location: https://weizmann.zoom.us/j/7621438333?pwd=c0lpdlQzYSthellXWG9rZnM0ZDRFZz09
    Lecturer: Eric Attias
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Conventional hydrogeologic models employed to compute ocean island sustainable y ... Read more Conventional hydrogeologic models employed to compute ocean island sustainable yields and aquifer storage neglect the nearshore and onshore submarine environment’s complexity. However, the onshore aquifer at the island of Hawaiʻi exhibits a significant volumetric discrepancy between high-elevation freshwater recharge and coastal discharge. This study presents a novel transport mechanism of freshwater moving from onshore to onshore via a multilayer formation of water-saturated layered basalts with interbedded low-permeability layers of ash/soil, as revealed by marine-controlled source electromagnetic (CSEM) imaging. We propose that this newly discovered transport mechanism of fresh water may be the governing mechanism in other volcanic islands. Additionally, our water column CSEM imaging detects multiple vertical freshwater plumes extending from the seafloor to the ocean surface. These findings provide valuable information to elucidate hydrogeologic and oceanographic rocesses affecting biogeochemical cycles in coastal waters worldwide.
    Close abstract

    MicroEco 2020

    Date:
    06
    Wednesday
    January
    2021
    -
    07
    Thursday
    January
    2021
    Conference
    Time: 08:00
    Location: David Lopatie Conference Centre

    Guest Seminar via Zoom - Plant and Environmental Sciences Dept.

    Date:
    05
    Tuesday
    January
    2021
    Lecture / Seminar
    Time: 11:30-12:30
    Title: Wild emmer wheat alleles promote drought adaptation mechanisms for changing climate
    Location: https://weizmann.zoom.us/j/97676258635?pwd=VGRFM3F1dXVMWFN4OFRvVzZZVlh3QT09 Password: 118210
    Lecturer: Harel Bacher
    Organizer: Department of Plant and Environmental Sciences
    Details: Host: Dr. Assaf Gal

    A coupled Eulerian-Lagrangian analysis of the large-scale tropical atmospheric circulation and its implication for climate change

    Date:
    27
    Sunday
    December
    2020
    Lecture / Seminar
    Time: 11:00
    Lecturer: Dana Reiter
    Organizer: Department of Earth and Planetary Sciences
    Abstract: The Hadley circulation is a key element of the climate system. It is traditional ... Read more The Hadley circulation is a key element of the climate system. It is traditionally defined as the zonally averaged meridional circulation in the tropics, therefore treated as a zonally symmetric phenomenon. However, differences in temperature between land and sea cause zonal asymmetries on Earth, dramatically affecting the circulation. This longitudinal dependence of the meridional circulation evokes questions about where and when the actual large scale tropical circulation occurs. Here, we look into the connection between the longitudinally dependent meridional circulation, and the actual large scale transport of air in the tropics using a coupled Eulerian and Lagrangian approach. Decomposing the velocity field into rotational and divergent components, we identify how each component affects the actual circulation. We propose an alternative definition for the circulation, that describes the actual path of air parcels in the tropics, as a tropical atmospheric conveyor belt. We further investigate this definition, analyzing the circulation under climate change and its effect on precipitation changes. We show that in order to predict future climate, the regionality and three-dimensionality of the large-scale tropical circulation must be taken into account. We find that the changes in the circulation vary significantly over longitude, and are overlooked when analyzing the zonally averaged meridional circulation. The circulation is strengthening and expanding in the center of the Pacific, a region where the circulation barely existed in past. On the other hand, the circulation is weakening in the Indo-Pacific region, where it was the most significant in the past. These differences appear as a shift in the region of ascent of the conveyor belt, that is revealed when analyzing the decomposed vertical wind. The pattern of weakening of the ascent in the Indo-Pacific and strengthening in the center of the Pacific explains the projected changes in precipitation. The Indo-Pacific region is drying, while the precipitation in the center of the Pacific is intensifying.
    Close abstract

    Reducing the Uncertainty of Extreme Weather and Climate Predictions

    Date:
    22
    Tuesday
    December
    2020
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Assaf Hochman
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Weather and climate extremes such as cold spells, heat waves, heavy precipitatio ... Read more Weather and climate extremes such as cold spells, heat waves, heavy precipitation or windstorms have long been considered challenging to adequately predict a few days in advance. Even at shorter time scales, it is sometimes difficult to estimate the magnitude and impact area accurately. Therefore, they have been selected as one of the grand challenges by the World Climate Research Program. Several studies suggest that extreme temperatures or heavy precipitation events may become more frequent and more intense with climate change, making this topic even more pertinent. The ability to predict the development of any dynamical system (a system that evolves in time), depends on: 1) its persistence, meaning that a persistent system will be easier to predict and 2) the number of options the system can develop into/from, meaning that systems with a small number of options will be easier to predict. Recent advances in dynamical systems theory allow to efficiently compute these metrics from model data. Our earlier findings show that the dynamical systems metrics can serve as an extremely informative qualitative method for evaluating the predictability and dynamics of synoptic systems over the Eastern Mediterranean. The talk will discuss this novel dynamic approach and its recent applications in extreme weather forecasting, as well as in climate model projections over the Eastern Mediterranean.
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    PHD Thesis Defense by Zoom - Plant and Environmental Sciences Dept.

    Date:
    15
    Tuesday
    December
    2020
    Lecture / Seminar
    Time: 13:00-14:00
    Title: The paradoxical role of the DMSP lyase enzyme during predator-prey interactions in the ocean
    Location: https://weizmann.zoom.us/j/92396176383?pwd=aVNKdEtZekhWWXhVZkVLeVF0YjBidz09 - password 866083
    Lecturer: Adva Shemi
    Organizer: Department of Plant and Environmental Sciences
    Details: Host: Prof. Assaf Vardi

    The diverse roles of bacterial chemical messengers: shaping marine communities and protecting phytoplankton against viral mortality

    Date:
    24
    Tuesday
    November
    2020
    Lecture / Seminar
    Time: 16:00
    Title: Guest Seminar by Zoom
    Location: https://weizmann.zoom.us/j/97551963167?pwd=ZWNFWjk3bmU3UThMV3habUdId085dz09 Meeting ID: 975 5196 3167 Password: 971660
    Lecturer: Dr. Kristen Whalen
    Organizer: Department of Plant and Environmental Sciences
    Details: Host: Dr. Einat Segev
    Abstract: Microbes have emerged as key players integrating a variety of external and inter ... Read more Microbes have emerged as key players integrating a variety of external and internal signals that simultaneously influence eukaryotic physiology. The coevolutionary history of microbes and their hosts has selected for a range of interactions from symbiotic to pathogenic, often driven by small molecule chemical messengers that shape community dynamics and govern ecosystem trajectories. However, an ongoing fundamental challenge for the field is identifying bacterial chemical signals and linking their mechanisms of action in the host with resultant ecological consequences in the field. Here, I will describe the mechanisms by which the bacterial quorum sensing signal 2-heptyl-4-quinolone (HHQ) induces immediate, yet reversible, cellular stasis (no cell division nor mortality) in the model coccolithophore, Emiliania huxleyi. Using ultrastructural observations and diagnostic biochemical assays integrated with transcriptomic and proteomic studies, I will describe the molecular targets of this bacterial signal and the mechanism(s) by which bacterial signals assist phytoplankton evasion from viral death. Since interactions between bacteria and eukaryotic phytoplankton play a central role in mediating biogeochemical cycles and global climate, this work provides a new mechanistic framework for how bacterial cues mediate interkingdom behaviors.
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    Insights on Processes in Polar Supercooled Cloud Lifecycles from Observations and Cloud Resolving Model Simulations

    Date:
    17
    Tuesday
    November
    2020
    Lecture / Seminar
    Time: 16:15
    Location: https://weizmann.zoom.us/j/98304295504?pwd=UmlnM3FMVG5pRHBTSFhhVTZEc3RRQT09
    Lecturer: Israel Silber
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Supercooled clouds substantially impact polar surface energy budgets but large-s ... Read more Supercooled clouds substantially impact polar surface energy budgets but large-scale models often underestimate their occurrence, which motivates accurately establishing metrics of basic processes. A polar stratiform cloud’s lifecycle is determined by a set of complex interactions and feedbacks between different micro-physical and macro-physical processes, some of which are not fully understood or quantified, leading to uncertainty in climate predictions. These polar clouds are commonly presupposed as being turbulent as a result of intense cloud-top longwave radiative cooling, while experiencing desiccation dominated by precipitating ice. In this talk, I examine some of these underlying assumptions and provide applicable guidance for large-scale model evaluation. I first present observations of persistent formation of drizzle drops at cloud temperatures below -25 °C detected over McMurdo Station, Antarctica. These supercooled drizzle observations supported by large-eddy simulations (LES) used to examine the cloud’s formation and evolution under initially stable, nonturbulent conditions, suggest that drizzle can be common over polar regions and serve as the main cloud moisture sink even well below the freezing temperature. A persistent nonturbulent cloud state suggested by the LES leads to the examination of nonturbulent cloud occurrence in observational datasets from Arctic and Antarctic ground-based sites. Such stable, nonturbulent conditions, surmised to preferentially occur early in cloud lifecycles, are estimated to prevail in a quarter of cloud occurrences over these polar sites. I use LES sensitivity tests to examine how short to intermediate period gravity waves, which are supported by such stable conditions, may catalyze turbulence formation when aerosol particles available for activation are sufficiently small. The observational datasets are also utilized to examine ice precipitation processes, and show that the vast majority of polar supercooled clouds are at least weakly precipitating ice at the cloud base even when they are not seeded from above, consistent with commonly observed supercooled cloud longevity. These results indicate that supercooled cloud layers are a sustained source of ice precipitation, and suggest that ground-based statistics offer valuable guidance for large-scale models. Finally, as an example of how some of these observational and modeling results may be used to evaluate the representations of polar clouds in large-scale models, I briefly describe using the GISS E3 climate model in single-column model (SCM) mode applied to the supercooled drizzle case study.
    Close abstract

    Why are there colors in the ocean?

    Date:
    10
    Tuesday
    November
    2020
    Lecture / Seminar
    Time: 14:30
    Title: Guest Seminar via Zoom
    Lecturer: Dr. Derya Akkaynak
    Organizer: Department of Plant and Environmental Sciences
    Details: https://weizmann.zoom.us/j/94626252637?pwd=VFBud0k2RGlFb1RhUzZ0bFpPdk9PQT09 Mee ... Read more https://weizmann.zoom.us/j/94626252637?pwd=VFBud0k2RGlFb1RhUzZ0bFpPdk9PQT09 Meeting ID: 946 2625 2637 Password: 637971
    Close details

    CANCELLED!! Guest Seminar via Zoom

    Date:
    03
    Tuesday
    November
    2020
    Lecture / Seminar
    Time: 11:30
    Title: Wild emmer wheat alleles promote drought adaptation mechanisms for changing climate
    Lecturer: Harel Bacher
    Organizer: Department of Plant and Environmental Sciences
    Details:

    Braginsky Center for the Interface between Science and the Humanities zoom lecture with Prof. Mario Livio

    Date:
    19
    Monday
    October
    2020
    Lecture / Seminar
    Time: 16:00-17:00
    Title: GALILEO and the Science Deniers
    Location: https://weizmann.zoom.us/j/99300972953?pwd=cWJ1Z2ZnUzh5MWJUNjB3enlCaWJUUT09
    Lecturer: Prof. Mario Livio
    Organizer: Braginsky Center for the Interface between Science and the Humanities
    Abstract: A fresh biography of Galileo Galilei which puts his scientific discoveries in co ... Read more A fresh biography of Galileo Galilei which puts his scientific discoveries in context. Disturbed by rampant science denial in America—and around the world—that has only intensified in recent years, I began researching the life, ideas, and actions of this brilliant man who encountered similar pressures centuries ago. The result is a biography filled with lessons relevant for today—whether with respect to trusting the advice given by scientists in relation to COVID-19, the reality of climate change, the efficacy of vaccines, or the teaching of creationist theories in schools. I will discuss these topics in this talk.
    Close abstract

    Why are there colors in the ocean?

    Date:
    10
    Thursday
    September
    2020
    Lecture / Seminar
    Time: 09:00
    Location: https://weizmann.zoom.us/j/94960131201?pwd=ZjB3RkdIYnRhNFB3U056Y0lzaUltZz09
    Lecturer: Derya Akkaynak
    Organizer: Department of Earth and Planetary Sciences

    Life and death in a pinch of salt: chronology, sedimentology, and geobiology of the Messenian Salinity Crisis deposits in the deep Levant Basin

    Date:
    31
    Sunday
    May
    2020
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Aaron Meilijson
    Organizer: Department of Earth and Planetary Sciences
    Abstract: The Messinian Salinity Crisis (MSC; 5.97-5.33 Ma) is considered an extreme envir ... Read more The Messinian Salinity Crisis (MSC; 5.97-5.33 Ma) is considered an extreme environmental event driven by changes in climate and tectonics, which affected global ocean salinity and shaped the biogeochemical composition of the Mediterranean Sea. Yet, after more than 50 years of research, MSC chronology and events remains controversial. Recently drilled offshore wells in the Levant Basin retrieved for the first time a complete sedimentary record of the deep-basin Mediterranean MSC salt deposits and the underlying Pre-Evaporite unit. Analysis of this dataset changes the way these deposits have been perceived since the 1970’s, when they were first penetrated in their uppermost part during DSDP expeditions. Using sedimentology, chemistry, seismic interpretation, biostratigraphy, and astronomical tuning we show that Messinian salt deposition in the Eastern Mediterranean began during stage 1, and not stage 2 of the MSC. In contrast to the present paradigm, salt was deposited synchronously with gypsum deposition in the marginal and intermediate-depth basins. This occurred significantly earlier than the 50 kyr interval coined as the ‘MSC acme event’, ~300 kyr after the crisis began. The one-kilometer-thick lower part of the evaporitic unit is composed of essentially pure halite, except for a thin transitional anhydrite layer at its base. The halite is undisturbed and homogeneous, lacking diverse features apparent in more proximal sections, indicating a deep-sea depositional environment. We find that distinct, meters-thick non-evaporitic intervals interbedded with the halite, previously thought to be clastic layers, are diatomites. While XRD analysis confirms an increase in clastic components in these sediments, they are composed primarily of well-preserved marine and freshwater planktonic diatoms. The occurrence of marine planktonic diatoms in these intervals indicates the input of Atlantic waters into the Mediterranean Basin during the deposition of the massive halite unit. In the second part of this talk I will couple lipid biomarker analysis with faunal and taxonomic evaluation of the diatom assemblages to try and answer the following question: why do we see this extreme abundance of diatoms, but a complete absence of calcareous-shelled forms of life within the MSC salt deposits? This study demonstrates that brine formation, salt precipitation, and faunal extinction occurred at least in part in a deep, non-desiccated basin, with a restricted yet open Mediterranean-Atlantic connection that allowed inflow of oceanic water. A coeval onset of basinal halite and marginal gypsum precipitation calls for a revaluation of global-scale climatic and oceanographic models of the MSC, while substantially altering our understanding of the mechanisms governing the deposition of salt giants.
    Close abstract

    Prof. Yohai Kaspi - How does the climate system work?

    Date:
    19
    Tuesday
    May
    2020
    Lecture / Seminar
    Time: 12:00
    Title: How does the climate system work?
    Location: Dolfi and Lola Ebner Auditorium
    Lecturer: Prof. Yohai Kaspi
    Organizer: Communications and Spokesperson Department
    Details: The lecture is in Hebrew

    Canceled: From an atomic-resolution mill to new engineering solutions for the climate crisis

    Date:
    29
    Sunday
    March
    2020
    Lecture / Seminar
    Time: 13:00-14:00
    Title: SAERI - Sustainability and Energy Research Initiative
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Dr. Ye Tao
    Organizer: Feinberg Graduate School
    Details: Canceled: Host: Prof. Ron Milo Light refreshments will be served at 12:40

    Exploring the limits of Earth’s habitability by scientific ocean drilling: The impact of temperature on microbial life and carbon flow in deep sub-seafloor sediments

    Date:
    23
    Sunday
    February
    2020
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Verena Heuer
    Organizer: Department of Earth and Planetary Sciences

    Special Guest Seminar

    Date:
    05
    Wednesday
    February
    2020
    Lecture / Seminar
    Time: 11:30-12:30
    Title: “Mining the marine microbiome for remediation targets: lessons from the human microbiome”
    Location: Arthur and Rochelle Belfer Building for Biomedical Research
    Lecturer: Dr. David Zeevi
    Organizer: Department of Molecular Genetics,Department of Plant and Environmental Sciences

    What will we eat tomorrow ? Food security in the 21st century

    Date:
    21
    Tuesday
    January
    2020
    Lecture / Seminar
    Time: 10:00-10:30
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Moshe Goldsmith
    Organizer: Department of Biomolecular Sciences
    Abstract: The world’s population is expected to grow by 25% in the next 30 years, reachi ... Read more The world’s population is expected to grow by 25% in the next 30 years, reaching 9.6 billion by 2050. In order to feed such a large population, there is a global need to increase food production from crops alone by 56%. In addition, global warming is expected to reduce crop yields in low and middle latitude areas and to increase climate instability. A partial solution can be found by transitioning to more resilient and nutritious food crops such as millets and legumes. However, some of these crops contain toxic compounds that pose a health risk if consumed at high amounts. Here we present our attempts to identify and eliminate such a plant toxin in order to produce a cultivar that is safe for large scale consumption.
    Close abstract

    “Exploring climate sensitivity using living and fossil plants”

    Date:
    07
    Tuesday
    January
    2020
    Lecture / Seminar
    Time: 11:30-12:30
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Dr. Margret Steinthorsdottir
    Organizer: Department of Plant and Environmental Sciences
    Details: Host: Dr. Tamir Klein

    The Critical Role of Chronology in Understanding Past Climate Change: Precisely Reconstructing Holocene Climate at Mono Lake, California

    Date:
    05
    Sunday
    January
    2020
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Susan R. H. Zimmerman
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Recent droughts and floods in California have drawn attention to the vulnerabili ... Read more Recent droughts and floods in California have drawn attention to the vulnerability of our water-supply system to present and future climate variability. A recent analysis of climate-model simulations suggests that wet and dry conditions in California may be predictably linked to tropical and high-latitude conditions, a hypothesis that should be testable using paleoclimate records. Abundant paleoclimate evidence indicates that natural whiplash between wet and dry conditions characterized California’s climate throughout the last 4000 years, especially during the Medieval Climate Anomaly (~AD 950 to 1250), but the chronologies of the records are not precise enough to correlate to tropical and high-latitude records in order to test the model prediction. Our recent work at Mono Lake, a climatically sensitive lake on the arid eastern side of the Sierra Nevada mountain range, has focused on exploring and developing radiocarbon dating of pollen purified by flow cytometry as a tool for high-resolution dating of lake records. Our results suggest that pollen can be reliably separated and dated, but (like everything in lakes) must be interpreted within the specific geologic system where it was produced, deposited, and preserved. If pollen dating proves robust in many lake systems, it may provide the high-precision chronologies required for spatial mapping of past terrestrial climate changes.
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    A mechanism for positive lapse-rate feedback in polar regions

    Date:
    30
    Monday
    December
    2019
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Prof. Rodrigo Caballero
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Observations and climate simulations show that polar regions warm faster than th ... Read more Observations and climate simulations show that polar regions warm faster than the rest of the globe in response to radiative forcing. Feedback diagnostics in models show that a large fraction of this enhanced polar warming is due to strong positive lapse-rate feedback. However, there is little mechanistic understanding for why this feedback is positive and what controls its strength. Here, I discuss a mechanism for high-latitude lapse rate feedback and show it functioning in a set of simplified GCM simulations. The mechanism hinges crucially on low cloud response. In this sense, high-latitude lapse-rate feedback is a cloud feedback in disguise.
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    Science-based policy and knowledge gaps regarding Israel's Marine Environment

    Date:
    15
    Sunday
    December
    2019
    Lecture / Seminar
    Time: 13:00-14:00
    Title: SAERI - Sustainability and Energy Research Initiative
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Dr. Dror Zurel
    Organizer: Feinberg Graduate School
    Details: Host: Prof. Ron Milo Light refreshments will be served at 12:40

    Science-based policy and knowledge gaps regarding Israel's Marine Environment

    Date:
    15
    Sunday
    December
    2019
    Lecture / Seminar
    Time: 13:00-14:00
    Title: SAERI - Sustainablity and Energy Research Initiative Seminar Series
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Dr. Dror Zurel
    Organizer: Feinberg Graduate School
    Details: Host: Prof. Ron Milo Light refreshments will be served at 12:40

    Evaporation from the ocean: A new Lagrangian model and its application to observations

    Date:
    15
    Sunday
    December
    2019
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Natan Paldor
    Organizer: Department of Earth and Planetary Sciences

    Internal Waves in the Ocean - what we know, and what we don't

    Date:
    26
    Tuesday
    November
    2019
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Yuri V Lvov
    Organizer: Department of Earth and Planetary Sciences

    Isotopic diagenesis of biogenic silica in marine sediments and implications for Cenozoic climate

    Date:
    24
    Sunday
    November
    2019
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Anastasia Yanchilina
    Organizer: Department of Earth and Planetary Sciences
    Abstract: The oxygen isotopic signature of marine deep-sea cherts was previously used to r ... Read more The oxygen isotopic signature of marine deep-sea cherts was previously used to reconstruct past ocean temperature and bottom water δ18O through the Cenozoic and Mesozoic periods. Oxygen isotopes of deep-sea cherts, which were never exposed to meteoric water, exhibit a wide range of values indicating that the evolution and maturation of biogenic amorphous opal (opal-A) to opal-CT and microquartz chert is accompanied by isotopic changes. We measured δ18O of diatom opal-A, opal-CT, and microquartz chert from deep sea cores retrieved from the Japan Sea. The δ18O of opal-CT and microquartz chert phases correspond to the depth in the sediments where these transitions occur, ~400 m and 40 °C for opal-A to opal-CT and ~500 m and 60 °C for opal-CT to microquartz chert. The δ18O values of opal-CT and microquartz chert appear to reflect equilibrium formation temperatures of silica, corresponding to the geothermal gradient and the local porewater δ18O. The δ18O of opal-CT and microquartz chert are controlled by the geothermal gradient and compositions of pore waters during polymorphic transformations deep within the sediment, indicating that the δ18O of these phases cannot be used to determine temperature or composition of seawater during diatom growth. Opal-A is the most susceptible phase for isotope alteration. We separated opal-A (i.e., diatoms, radiolaria, and siliceous sponge spicules) of Cenozoic age and measured its isotope composition. The results do not indicate any significant change in δ18O. This will be discussed within the general framework of global climatic change.
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    Distinctive aspects of carbon, water and energy partitioning in a semi-arid forest ecosystem

    Date:
    18
    Monday
    November
    2019
    Colloquium
    Time: 11:00-12:15
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Dan Yakir
    Organizer: Faculty of Chemistry
    Abstract: Arid and semi-arid regions belong to the most vulnerable climate change “hot s ... Read more Arid and semi-arid regions belong to the most vulnerable climate change “hot spots” while also contributing to global scale variations in the carbon and water cycles. In particular, this is because of their high sensitivity to changes in precipitation and surface energy budgets and to the large changes in land-use taking place in these regions. This requires improving the representation of these ecosystems in land surface and ecosystem models. Improving observational approaches is also required to assess variations in their water carbon and energy exchange and to identify underlying processes. The more exotic observational sites, such as those at the semi-arid ‘timber-line’, do not always fit the large-scale patterns, but provide important test beds for predicted changes in ecosystem functioning. I will review a few examples from the Yatir site operating at the edge of the Negev desert for past 20 years, to demonstrate distinctive ecosystem response to environmental conditions and its implications.
    Close abstract

    Ocean Worlds of the Outer Solar System: Life as we know it or life as we don’t?

    Date:
    03
    Sunday
    November
    2019
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Alex Hayes
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Recent discoveries have shown that habitable environments likely exist in subsur ... Read more Recent discoveries have shown that habitable environments likely exist in subsurface water oceans within the outer planet moons of Europa and Enceladus. On Titan, the largest moon of Saturn, lakes and seas of liquid hydrocarbon exist in addition to a vast subsurface water ocean. These places represent ideal locations for hydrothermal environments that could sustain life as we know it and, in Titan’s case, perhaps even life as we don’t. The next generation of uncrewed planetary spacecraft will be designed to search for the signs of life in one or more of these worlds. This lecture will begin with a brief review of the discoveries that have motivated a renewed importance for Ocean World exploration, before diving into Titan's lakes and seas to discuss recent findings related to its hydrocarbon-based hydrologic cycle and setting the stage for the newly selected Dragonfly quadcopter set to explore Titan in the mid 2030s.
    Close abstract

    Forecast Skill and the Impact of Equatorial Waves in Two Operational Weather Prediction Systems

    Date:
    18
    Wednesday
    September
    2019
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: George N. Kiladis
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Equatorially trapped waves account for a large portion of the perturbations with ... Read more Equatorially trapped waves account for a large portion of the perturbations within the tropical atmosphere and ocean. In the atmosphere, these disturbances are coupled to convection and determine a significant amount of rainfall variability on synoptic to intraseasonal time scales. Numerical models used for both weather and climate forecasting universally still have great difficulty simulating these convectively coupled disturbances. We assess the quantitative precipitation forecasts (QPF) skill of NOAA's Global Forecast System (GFS) and the European Centre for Medium Range Weather Forecasting Integrated Forecast System (IFS) operational models used for short term forecasts out to 10 days. Forecast skill was assessed by comparison with virtually independent GPM and CMORPH satellite precipitation estimates. Skill was quantified using a variety of metrics including pattern correlations for various latitude bands, temporal correlation at individual grid points, and space-time spectra of forecast precipitation over the global tropics and extratropics. Results reveal that, in general, initial conditions are reasonably well estimated in both forecast systems, as indicated by relatively good scores for the 6-12 hour forecasts. Since precipitation estimates are not directly assimilated into these systems, this indicates that the initialization of dynamical and thermodynamical fields is able to produce a reasonable QPF field, at least for the larger scales. We present evidence that the specification of the mass circulation rather than the moisture field is the primary source of this initial skill. Model skill is substantially better overall in the extratropics, however, tropical QPF in both systems is not considered useful by typical metrics much beyond a few days. A portion of this lack of tropical skill in can be traced back to inadequate treatment of equatorial wave activity coupled to convection. It is also demonstrated that extratropical forecast skill is positively correlated to preceding tropical skill, strongly suggesting that improvements in the treatment of tropics will lead to improved extratropical forecasts on the weekly and longer timescale.
    Close abstract

    Learning to Love CO2: Carboxylation, Catalysis, and Desalination

    Date:
    03
    Tuesday
    September
    2019
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Helen and Milton A. Kimmelman Building
    Lecturer: Prof. Ji-Woong Lee
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: Currently, more than 40 gigatonnes of CO2 are released annually into the atmosph ... Read more Currently, more than 40 gigatonnes of CO2 are released annually into the atmosphere as a result of fossil fuel combustion, causing ocean acidification and climate unpredictability. Anthropogenic CO2 emission is seemingly hard to diminish in the near future and, therefore, CO2 -capture and sequestration or CO2 -functionalization can be viable solutions to address this issue. To use CO2 as a chemical feedstock, namely as a C1 building block, it is essential to equip the process with a nucleophilic catalyst or a highly active reagent, as exemplified by Grignard carboxylation reactions and some recent progress in metal-catalyzed reactions. In this seminar, I will display how we can utilize CO2 not only as a chemical feedstock and a catalyst but also as a stimulus for a desalination process. The obtained knowledge in CO2 activation and desalination will be beneficial in supramolecular chemistry, biology, CO2functionalization catalysis and CO2 sequestration processes.
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    PhD Thesis Defense:

    Date:
    10
    Wednesday
    July
    2019
    Lecture / Seminar
    Time: 11:00-12:00
    Title: From cellular processes to ecological impact – Investigating bacterial interactions with the bloom-forming marine phytoplankter Emiliania huxleyi
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Noa Barak-Gavish
    Organizer: Department of Plant and Environmental Sciences

    The role of clouds in extratropical climate change and variability

    Date:
    02
    Sunday
    June
    2019
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: David Thompson
    Organizer: Department of Earth and Planetary Sciences

    Biogeochemical cycling of trace elements in the oceans: lessons from coeval time series of dust, marine particulates and seawater in the Red Sea

    Date:
    07
    Tuesday
    May
    2019
    Lecture / Seminar
    Time: 11:30
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Dr. Adi Torfstein
    Organizer: Department of Plant and Environmental Sciences
    Details: Host: Dr. Einat Segev

    The pathway of atmospheric water from ocean evaporation to rainout in extratropical weather systems

    Date:
    05
    Sunday
    May
    2019
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Heini Wernli
    Organizer: Department of Earth and Planetary Sciences

    Period doubling as an early warning signal for desertification

    Date:
    29
    Monday
    April
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Omer Tzuk
    Organizer: Department of Physics of Complex Systems
    Abstract: The predictions for a warmer and drier climate and for increased likelihood of c ... Read more The predictions for a warmer and drier climate and for increased likelihood of climate extremes raise high concerns about the possible collapse of dryland ecosystems, and about the formation of new drylands where native species are less tolerant to water stress. Using a dryland-vegetation model for plant species that display different tradeoffs between fast growth and tolerance to droughts, we find that ecosystems subjected to strong seasonal variability, typical for drylands, exhibit a period-doubling route to chaos that results in early collapse to bare soil. We further find that fast-growing plants go through period doubling sooner and span wider chaotic ranges than stress-tolerant plants. We propose the detection of period-doubling signatures in power spectra as early indicators of ecosystem collapse that outperform existing indicators in their ability to warn against climate extremes and capture the heightened vulnerability of newly-formed drylands.
    Close abstract

    The genetics of epigenetics

    Date:
    16
    Tuesday
    April
    2019
    Lecture / Seminar
    Time: 11:30
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Prof. Magnus Nordborg
    Organizer: Department of Plant and Environmental Sciences
    Details: Host: Tal Dahan If you wish to meet Prof. Nordborg, please contact tal.dahan@we ... Read more Host: Tal Dahan If you wish to meet Prof. Nordborg, please contact tal.dahan@weizmann.ac.il
    Close details
    Abstract: Epigenetics continues to fascinate, especially the notion that it blurs the line ... Read more Epigenetics continues to fascinate, especially the notion that it blurs the line between “nature and nurture” and could make Lamarckian adaptation via the inheritance of acquired characteristics possible. That this is in principle possible is clear: in the model plant Arabidopsis thaliana (thale cress), experimentally induced DNA methylation variation can be inherited and affect important traits. The question is whether this is important in nature. Recent studies of A. thaliana have revealed a pattern of correlation between levels of methylation and climate variables that strongly suggests that methylation is important in adaptation. However, somewhat paradoxically, the experiments also showed that much of the variation for this epigenetic trait appears to have a genetic rather than an epigenetic basis. This suggest that epigenetics may indeed be important for adaptation, but as part of a genetic mechanism that is currently not understood. Genome-wide association studies revealed a striking genetic architecture of methylation variation, involving major-effect polymorphisms in many genes involved in silencing, and this can be utilized to determine whether the global pattern of methylation variation has a genetic or an epigenetic cause, and to elucidate the ultimate cause of the global pattern of variation: natural selection.
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    Digitally draining the oceans (so we can see what’s inside)

    Date:
    08
    Monday
    April
    2019
    Lecture / Seminar
    Time: 10:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Derya Akkaynak
    Organizer: Department of Earth and Planetary Sciences

    Growth, exudation, death and zombihood in abundant marine phytoplankton

    Date:
    29
    Tuesday
    January
    2019
    Lecture / Seminar
    Time: 11:30
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Dr. Daniel Sher
    Organizer: Department of Plant and Environmental Sciences
    Details: Host: Dr. Einat Segev