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It’s an Emergency: What It Means to Be a Scientist in an Era of Climate and Ecological Breakdown

Date:
30
Sunday
March
2025
Lecture / Seminar
Time: 13:00-14:00
Title: IES- Institute For Environmental Sustainability Initiative seminar series 2025-2026
Location: Nella and Leon Benoziyo Building for Plant and Environmental Sciences
Lecturer: Dr. Avner Gross
Organizer: The Institute for Environmental Sustainability

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    Reduced N-fixation in the Low Latitude Atlantic during the Warmer Pliocene

    Date:
    23
    Sunday
    March
    2025
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Maayan Yehudai
    Abstract: N2 fixation is the primary pathway by which bioavailable nitrogen is added to th ... Read more N2 fixation is the primary pathway by which bioavailable nitrogen is added to theoceans. However, the drivers of N2 fixation on orbital timescales are uncertain. Wepresent high-resolution foraminifera-bound (FB) δ15N records from the Westernand Eastern tropical Atlantic Ocean (WTA and ETA respectively) throughout thelate Pliocene (~3.60 to ~1.97 Ma), where WTA ODP Site 999 represents N2fixation changes and EEA ODP Site 662 represents changes in pycnocline δ15N.Our results show that, compared to the past 160 ka, N2 fixation in the WTA wassignificantly lower throughout the late Pliocene as reflected by an average of ~2 ‰higher FB-δ15N values. A possible explanation to the higher Pliocene FB-δ15N inthe WTA could be lower rates of global denitrification that were balanced by lowerglobal N2 fixation levels. We suggest that this reduced N2 fixation was due todecreased excess P in the pycnocline/subsurface ocean, driven by lower globalwater column denitrification. This finding implies a coupling between decreasedwater column denitrification and reduced level N2 fixation rates under warmerclimates.On orbital timescales, our N2 fixation record display obliquity-paced cycles thatprogressively intensified after the Northern Hemisphere glaciation intensification ~2.8 Ma, and the onset of equatorial upwelling pulses documented during glacialperiods in the EEA (ODP Site 662; [1]). The observed changes in N2 fixation of thelast 160 ka were previously explained by precession-paced upwelling in the EEAthat imported excess P into the oligotrophic WTA [2]. However, precessionalcyclicity is not dominant in the Pliocene FB- δ15N, which calls for other candidatesto explain the variations after 2.8 Ma. The best explanation is a response to sealevelpaced sedimentary denitrification. Glacial lower sea levels exposedcontinental shelves, reducing regional benthic denitrification and inhibiting thesupply of excess P, thereby limiting N2 fixation in the WTA, whereas interglacialsubmerged shelves increased excess P availability.
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    The Holocene temperature and CO2 conundrum: a long-term perspective from earlier interglacials

    Date:
    16
    Sunday
    March
    2025
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Yair Rosenthal
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: The pre-industrial Holocene is unique among pastinterglacials due to a modest, b ... Read more The pre-industrial Holocene is unique among pastinterglacials due to a modest, but notable increase inatmospheric CO2 and methane (CH4) during the latter halfof the period despite an expected decrease given orbitalparameters. Although the causes for this increase,anthropogenic or natural are debated, all climate modelssimulate an increase in global mean temperature inresponse to the increase in the greenhouse gases. Yet,many proxy reconstructions, interpreted to reflect themean annual temperatures, indicate peak temperatures inthe first half of the Holocene, arguably exceeding modernmean annual temperatures followed by cooling through thepreindustrial period. This significant model-datadiscrepancy, known as the Holocene temperatureconundrum, and the debate on the cause of the CO2increase has undermined confidence in future climatemodel predications. In this talk I’ll offer new perspectiveson both issues.
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    The Clore Center for Biological Physics

    Date:
    23
    Sunday
    February
    2025
    Lecture / Seminar
    Time: 13:15-14:30
    Title: What can microbes tell us about their environment
    Location: Nella and Leon Benoziyo Physics Library
    Lecturer: Dr. David Zeevi
    Contact: debbie.hen@weizmann.ac.il
    Abstract: Microbial communities act as living sensors of their environment, continuously a ... Read more Microbial communities act as living sensors of their environment, continuously adapting to and recording changes in their surroundings across temporal and spatial scales. This capacity, combined with their central role in global biogeochemical cycles, makes microbes ideal indicators of ecosystem health. However, our understanding of how these communities respond to anthropogenic perturbations remains limited. In this talk, I will present two complementary approaches to decode environmental information from microbial communities. First, I will show that environmental temperature can be accurately predicted from microbial DNA composition alone, revealing fundamental principles of genome-wide thermal adaptation that transcend ecosystem boundaries. This work uncovers how evolutionary pressures shape microbial genomes across diverse habitats and provides insights into long-term community responses to climate change. Second, I will introduce a novel approach for measuring real-time bacterial growth rates in natural environments from a single sample, without prior knowledge on community composition. This method could enable us to track immediate ecological responses to environmental perturbations. By combining these evolutionary and ecological perspectives, we can begin to establish universal principles governing microbial responses to environmental change across different timescales. This multi-scale understanding is crucial for predicting and potentially mitigating the impacts of human activities on microbial ecosystems, from soil degradation to climate change.FOR THE LATEST UPDATES AND CONTENT ON SOFT MATTER AND BIOLOGICAL PHYSICS AT THE WEIZMANN, VISIT OUR WEBSITE: https://www.biosoftweizmann.com/
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    Submesoscale ocean circulation: plenty of room at the bottom

    Date:
    23
    Sunday
    February
    2025
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Aviv Solodoch
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: Sub-mesoscale (SMS, <10 km scale) ocean circulation is characterized by high ... Read more Sub-mesoscale (SMS, <10 km scale) ocean circulation is characterized by high vorticity and deviation from geostrophic balance. It can result in large effects on biology and chemistry due to the large vertical velocities (x10-100 than mesoscale) and resulting down/up welling circulations, as well as significant effects on material retaining and dispersion. Modelling and observing the Submesoscale is challenging due to stringent demands on spatio-termpoal resolution, and due to its strong interactions with both larger (mesoscale) and smaller (turbulence and waves) circulations. I will report on the first Sub-mesoscale-resolving numerical modelling study in the East Mediterranean Sea, and (likely universal) findings on the patterns of cross-scale energy exchange between the Sub-Mesoscale and mesoscale circulation, which controls the seasonal evolution of both circulations. Secondly I will show in the model boundary current variability can spawn Sub-Mesoscales year-round (while open ocean formation is largely limited to winter). This will be backed by our (and the first) systematic observations of a Sub-mesoscale vortex formed in summertime via boundary current meandering.  
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    Interactions between cyclones and mesoscale eddies in the Mediterranean Sea

    Date:
    16
    Sunday
    February
    2025
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Ehud Strobach
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: Mesoscale eddies dominate global ocean kinetic energy and are responsible for ef ... Read more Mesoscale eddies dominate global ocean kinetic energy and are responsible for efficiently transferring ocean properties. The influence of ocean eddies in the western boundary currents on storm tracks has been studied in recent years, and their importance in regulating mid-latitude precipitation is now recognized. Unlike western boundary currents, mesoscale eddies in the Mediterranean Sea (MS) are smaller and less intense. Yet, the MS is rich in mesoscale activity, and its proximity to densely populated regions suggests that even a small change may have a large impact, which remains underexplored. In this talk, I present several recent studies in which we investigated the interactions between mesoscale eddies and cyclones in the Mediterranean region. These studies focused on specific Mediterranean tropical-like cyclones (medicanes), analyzing their evolution under different sea conditions using observations and model simulations. We find that mesoscale eddies in the MS can change the intensity and track of cyclones and, consequently, affect their resulting rainfall distribution over land. In general, warm-core eddies tend to intensify cyclones and increase precipitation above them relative to cold-core eddies. Additionally, we observe a general increase in surface ocean biogeochemical properties, such as phytoplankton and chlorophyll, following cyclone passages. This increase is driven by upwelling and vertical mixing, though the relative importance of these processes differs between warm- and cold-core eddies.
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    Climate and Solar Variability: A Critical Evaluation

    Date:
    09
    Sunday
    February
    2025
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Nathan Steiger
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: It has been claimed that solar variability is the largest driver of climatic var ... Read more It has been claimed that solar variability is the largest driver of climatic variability across thePhanerozoic eon and that it accounts for ½ to ⅔ of20th century warming. Apparent evidence insupport of these claims has been mustered frommodeling work along with paleoclimatic, oceanographic, and other observational datasets.Here I will show that this research fails to replicate. I additionally find that many studies claiming tosupport a strong solar-climate link suffer from fundamental statistical and conceptual errors thatinvalidate their results.
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    Methane mitigation by unique redox couplings in freshwater sediments

    Date:
    02
    Sunday
    February
    2025
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Orit Sivan
    Abstract: This talk tests the ability of natural freshwater lakes and margins to attenuate ... Read more This talk tests the ability of natural freshwater lakes and margins to attenuate the emissions ofthe greenhouse gas methane (CH4) to the atmosphere under warming climate. I will show howmicrobial communities manage to survive and mitigate methane emissions under energylimited, highly reduced conditions of deep methanogenic lake sediments, through redoxcouplings of methane to Mn-Fe-N. Complex redox couplings between those species were alsoexplored in thermokarst lakes and margins, which are extensively formed by permafrost thawin the Arctic. The cycles were quantified using geochemical and microbial profiles, togetherwith stable isotope probing experiments close to natural conditions. The profiles andincubations show active microbial population that exhibit surprisingly both aerobic andanaerobic methane oxidation in methanogenic sediments and upland Arctic soils, fueled bynitrogen and iron redox cycles.
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    Allochthonous groundwater microorganisms affect coastal seawater microbial abundance, activity and diversity

    Date:
    19
    Sunday
    January
    2025
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Sussman building
    Abstract: Submarine groundwater discharge (SGD) is a globally important processsupplying n ... Read more Submarine groundwater discharge (SGD) is a globally important processsupplying nutrients and trace elements to the coastal environment, thusplaying a pivotal role in sustaining marine primary productivity. Along withnutrients, groundwater also contains allochthonous microbes that aredischarged from the terrestrial subsurface into the sea. Currently, little isknown about the interactions between groundwater-borne and coastalseawater microbial populations, and groundwater microbes' role uponintroduction to coastal seawater populations. In the current study weinvestigated seawater microbial abundance, activity and diversity in a sitestrongly influenced by SGD. In addition, through laboratory-controlledbottle incubations, we mimicked different mixing scenarios betweengroundwater and seawater. Our results demonstrate that the addition of0.1 μm filtered groundwater stimulated heterotrophic activity andincreased microbial abundance compared to control coastal seawater,whereas 0.22 μm filtration treatments induced primary productivity andSynechococcus growth. 16S rRNA gene sequencing showed a strongshift from a SAR11-rich community in the control samples toRhodobacteraceae dominance in the <0.1 μm treatment, in agreementwith Rhodobacteraceae enrichment in the SGD field site. These resultssuggest that microbes delivered by SGD may affect the abundance,activity and diversity of intrinsic microbes in coastal seawater, highlightingthe cryptic interplay between groundwater and seawater microbes incoastal environments, which has important implications for carboncycling.
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    Making Climate Tech Work – Policies that Drive Innovation

    Date:
    22
    Sunday
    December
    2024
    Lecture / Seminar
    Time: 13:00-14:00
    Location: Nella and Leon Benoziyo Building for Plant and Environmental Sciences
    Lecturer: Prof. Alon Tal
    Organizer: Sustainability and Energy Research Initiative (SAERI)
    Contact: merav.hagag@weizmann.ac.il

    Multi-level ecosystem response to drying climate trends

    Date:
    22
    Sunday
    December
    2024
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Ehud Meron
    Abstract: Climate change and the development of drier climates threatenecosystems’ healt ... Read more Climate change and the development of drier climates threatenecosystems’ health and the services they provide to humans.Understanding ecosystem response to drier climates may provide clueson improving their functioning and resilience. This response is likely toinvolve mechanisms operating at different levels of ecologicalorganization. At the single-plant level, phenotypic changes can occur; atthe population level, spatial patterns can form; and at the communitylevel, community reassembly and biodiversity changes can occur.These mechanisms must affect one another, as stress relaxation byone mechanism weakens the driving forces of other mechanisms, butcomplex ecosystem responses involving coupled mechanisms havehardly been studied. In this talk I will focus on the interplay betweenphenotypic changes and spatial patterning and between spatialpatterning and community reassembly. Using mathematical models ofwater-limited plant communities, I will show that incorporatingphenotypic plasticity into vegetation pattern-formation theory canresolve two outstanding puzzles associated with the fascinatingNamibian fairy circle phenomenon and describe a predicted bufferingeffect of spatial patterning on community composition along rainfallgradients. Possible implications of these results to ecosystemfunctioning in stressed environments will be discussed.
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    ABC CHATS: Shira Eting

    Date:
    18
    Wednesday
    December
    2024
    Lecture / Seminar
    Time: 14:00-15:30
    Title: Based on values, Delivering value
    Location: George and Esther Sagan Students' Residence Hall
    Lecturer: Shira Eting - Vintage Investment Partners
    Contact: Reut.magor@weizmann.ac.il
    Abstract: During her conversation, Shira will share her personal journey and share what ha ... Read more During her conversation, Shira will share her personal journey and share what has led her to each decision and what are her key learnings.She will also share more about her position today as a Partner at Vintage, leading their investments in Healthcare and Climate.Join our ABC CHATS, Where CEOs share their ABC’s on scientific leadership, breakthroughs and failures throughout their personal stories
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    Multi-level ecosystem response to drying climate trends

    Date:
    17
    Tuesday
    December
    2024
    Lecture / Seminar
    Time: 16:46-17:46
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Ehud Meron

    Fundamentals of Remote Sensing and Machine Learning for Earth Science

    Date:
    01
    Sunday
    December
    2024
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Anna Brook
    Organizer: Department of Earth and Planetary Sciences
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: Our Laboratory focuses on research that drives technological, environmental and ... Read more Our Laboratory focuses on research that drives technological, environmental and social change. It includes advanced technologies in the social aspect of environment management, embracing the complexity of the human-environment relationship, and physical model development for complex and non-trivial real-world problems in the era of climate change. Our ultimate goal is to bridge the gap between machine learning and geoscience for sustainability and environmental management at the national and international (mainly in the Mediterranean) scales. We understand that machine learning, in general, and deep learning, in particular, offer promising tools to build new data-driven models for Earth system components and thus build our understanding of ecosystems. Yet, accepting that data-driven machine learning approaches in geoscientific research cannot replace physical modelling but strongly complement and enrich it. Our primary scientific interests are developing hybrid approaches, coupling physical processes (physical laws and physics-domain-specific knowledge) with the versatility of data-driven machine learning, also known as physics-aware machine learning, to better understand the ecosystems, biodiversity, dynamic processes and environmental responses to stressors, and emphasizing sustainability and decision support system development aligned with the UN Sustainable Development Goals (SDGs).
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    PhD thesis defense- Avia Mizrachi

    Date:
    11
    Monday
    November
    2024
    Lecture / Seminar
    Time: 14:00-15:00
    Title: Phenotypic variability and cell fate determination in marine diatoms in response to environmental stress
    Location: Nella and Leon Benoziyo Building for Plant and Environmental Sciences
    Lecturer: Avia Mizrachi
    Organizer: Department of Plant and Environmental Sciences
    Contact: avia.mizrachi@weizmann.ac.il

    Late Oxygenation of Marine Environments Revealed by Dolomite U-Pb Dating

    Date:
    10
    Sunday
    November
    2024
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Uri Ryb
    Organizer: Department of Earth and Planetary Sciences
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: causal relationships between evolution and oxygenation of the ocean are vigorou ... Read more causal relationships between evolution and oxygenation of the ocean are vigorously debated. At the heart of these uncertainties are inconsistencies among reconstructed timelines for the rise of O2 in marine habitats. Attempts to reconstruct the timing of marine oxygenation are often based on redox-sensitive geochemical proxies that are prone to post-depositional alteration. Thus, developing new proxies, more resistant to such alteration, is an important direction forward for constraining major changes in atmospheric and marine oxygen levels. Here, we utilize U–Pb dating in dolomite to reconstruct their (re)crystallization ages and initial 207Pb/206Pb ratios; we find that they are systematically younger and lower than expected, respectively. These observations are explained by the resetting of the U–Pb system long after deposition, followed by further evolution in a closed system. Initial 207Pb/206Pb ratios have decreased from expected terrestrial values in the interval between deposition and (re)crystallization, consistent with U decay, and can therefore be used to reconstruct the initial 238U/206Pb ratios during deposition. Within our dataset initial 238U/206Pb ratios remained low in Proterozoic to mid-Paleozoic samples and increased dramatically in samples from the late-Paleozoic–early- Mesozoic Eras. This rise is attributed to a higher ratio of U to Pb in seawater that in turn influenced the fluid composition of carbonate crystallization sites. Accordingly, we interpret the temporal shift in initial 238U/206Pb ratios to reflect a late-Paleozoic increase in oxygenation of marine environments, corroborating previously documented shifts in some redox-sensitive proxies. This timeline is consistent with evolution-driven mechanisms for the oxygenation of late Paleozoic marine environments and with suggestions that Neoproterozoic and early Paleozoic animals thrived in oceans that overall and on long time scales were oxygen-limited compared to the modern ocean.
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    Data synthesis to assess the effects of climate change on agricultural production and food security

    Date:
    30
    Sunday
    June
    2024
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: David Makowski
    Organizer: Department of Earth and Planetary Sciences
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: Climate change is having an impact on agricultural production and food security ... Read more Climate change is having an impact on agricultural production and food security. Rising temperatures, changes in rainfall patterns and extreme weather events can reduce crop yields, sometimes dramatically. However, climate change can also offer new opportunities, by generating more favorable climatic conditions for agricultural production in certain regions that were previously less productive. In order to assess the positive and negative impacts of climate change on agriculture and identify effective adaptation strategies, scientists have produced massive amounts of data during the last two decades, conducting local experiments in agricultural plots and using models to simulate the effect of climate on crop yields. In most cases, these data are not pooled together and are analyzed separately by different groups of scientists to assess the effects of climate change at a local level, without any attempt to upscale the results at a larger scale. Yet, if brought together, these data represent a rich source of information that are relevant to analyze the effect of climate across diverse environmental conditions. The wealth of data available has led to the emergence of a new type of scientific activity, involving the retrieval of all available data on a given subject and their synthesis into more robust and generic results. In this talk, I review the statistical methods available to synthesize data generated in studies quantifying the effect of climate change on agriculture. I discuss both the most classic methods - such as meta-analysis - and more recent methods based on machine learning. In particular, I show how this approach can be used to map the impact of climate change on a large scale (national, continental and global) from local data. I illustrate these methods in several case studies and present several research perspectives in this area.
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    Plan A+ - How geoengineering using stratospheric aerosols could play a role in climate policy

    Date:
    16
    Sunday
    June
    2024
    Lecture / Seminar
    Time: 13:00-14:00
    Location: https://weizmann.zoom.us/j/98884644964?pwd=SUF0cnVEZndYWmw1azFPQlhrTStuQT09
    Lecturer: Dr. Peter Irvine
    Organizer: Sustainability and Energy Research Initiative (SAERI)
    Contact: yuval.rosenberg@weizmann.ac.il
    Details: https://weizmann.zoom.us/j/98884644964?pwd=SUF0cnVEZndYWmw1azFPQlhrTStuQT09 Mee ... Read more https://weizmann.zoom.us/j/98884644964?pwd=SUF0cnVEZndYWmw1azFPQlhrTStuQT09 Meeting ID: 988 8464 4964 Password: 149775
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    Floods in a warming climate: what are the missing puzzle pieces?

    Date:
    19
    Sunday
    May
    2024
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Efrat Morin
    Organizer: Department of Earth and Planetary Sciences
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: Flood is the outcome of complex processes interacting at a range of scales. Floo ... Read more Flood is the outcome of complex processes interacting at a range of scales. Flood generation and its magnitude depend on different precipitation and surface properties. As the climate becomes warmer globally, precipitation patterns are changing and, consequently, altering flood regimes. Resolving the expected changes in flood properties requires examining projections of precipitation features most correlated with floods. While the redistribution of mean annual precipitation amounts is generally known, the trends in many other essential factors controlling floods are yet to be resolved. For example, flash flood magnitude is sensitive to space-time rainstorm properties such as areal coverage or storm speed. Still, knowledge of how these properties are affected by global warming is lacking. Maximal rain rates for duration relevant to the watershed’s response time are also crucial parameters controlling the flood discharge. There is some understanding of how extreme rain rates change, but the magnitude and sign depend on the rain duration considered. Changes in frequency and the intra-seasonal distribution of precipitation events also affect flood regimes. Finally, watersheds of different properties are sensitive to different precipitation features, and thus, different watersheds may respond differently to global warming. In this talk, we will present the complexity of flood response under global warming and then focus on two questions: 1) how does global warming affect heavy precipitation events (HPEs) in the eastern Mediterranean, and 2) how these effects are imprinted in the resulting floods in small-medium Mediterranean watersheds. We simulated 41 eastern Mediterranean HPEs with the high-resolution weather research and forecasting (WRF) model. Each event was simulated twice: under historical conditions and at the end of the 21st-century conditions (RCP8.5 scenario) using the “pseudo global warming” approach. Comparison of precipitation patterns from the paired simulations revealed that heavy precipitation events in our region are expected to become drier and more spatiotemporally concentrated, i.e., we expect higher rain rates on smaller coverage areas and shorter storm durations that, in total, yield lower amounts of rainfall. These effects have some contradicting signs, and their full hydrological impact on streamflow peak discharge and volume was further explored. Ensembles of spatially-shifted rainfall data from the simulated HPEs were input to a high-resolution distributed hydrological model (GB-HYDRA) representing four small-medium-size watersheds (18–69 km2) in the eastern Mediterranean (Ramot Menashe). Flow volume is significantly reduced in future HPEs, while the change in flood peak is more complicated due to the combined effect of precipitation amount (decreasing) and precipitation rate (increasing). For the watersheds examined in this research, which are mostly agricultural, flood peaks at the watershed outlets are mostly reduced. The dynamics of flood generation at sub-watersheds of different sizes and properties are further examined in this research to understand scenarios for lowering or increasing flood peaks. This study emphasizes that detecting and quantifying global warming impact on space-time precipitation patterns is essential for flood regime projection.
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    Lake Kinneret in a Changing Environment

    Date:
    12
    Sunday
    May
    2024
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Yael Amitai
    Organizer: Department of Earth and Planetary Sciences
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: Located in a highly sensitive subtropical climate area and a densely populated a ... Read more Located in a highly sensitive subtropical climate area and a densely populated area, Lake Kinneret is poised to undergo both natural and human-induced transformations in the coming decades. The lake is thermally stratified throughout most of the year and mixes thoroughly each winter when the epilimnion (upper layer) water temperature reaches equilibrium with the hypolimnion (bottom layer) water temperature by surface cooling and turbulence. Both the stratified and the fully mixed periods has a significant role in the Kinneret’s ecological system. Observation shows that air above the Lake is warming in a rate of 0.4oC/decade, while the epilimnion and hypolimnion are warming in a rate of 0.3oC/decade and 0.1oC/decade, respectively, for the last 50 years. Therefore, stratification strength and duration is anticipated to change and impact the lake’s ecosystem. Additionally, the sequence of drought periods and the expected future rise in water demands from Lake Kinneret formed the basis for the government's decision to channel desalinated water, via the natural course of the Tzalmon Stream, to the lake to ensure its operational functionality at high levels. Using a 3D hydrodynamic model forced by short and long-term forecasts the above scenarios are examined and analyzed. A simulation forced by regional atmospheric RCP4.5 climate change scenario spanning from 2010-2070 show continuous warming followed by abrupt cooling of the lake water around the year 2065. This result, presumably due to enhanced latent heat loss, suggest a restrain the dramatic anticipated change in the lake stratification.
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    Benthic side control on the chemical composition of the ocean

    Date:
    07
    Sunday
    April
    2024
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Zvi Steiner
    Organizer: Department of Earth and Planetary Sciences
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: The sediment – bottom-water interface is suggested as a key control on the ch ... Read more The sediment – bottom-water interface is suggested as a key control on the chemical composition of the ocean by studies of trace elements in the ocean water-column, yet data regarding trace element fluxes and interactions taking place in the top ten cm of abyssal sediments are scarce. To bridge this gap, I analysed the trace and major element composition of porewater and sediment of red-clay sediment from the abyssal North Pacific, and hydrothermally influenced sediment from the Mid-Atlantic Ridge. The top sediment at both study regions is aerobic, nevertheless, there is large variability in the porewater concentrations of many elements at the top five cm. The North Pacific red-clay sediment is a source of cobalt, nickel, copper, arsenic, vanadium and barium to the deep-ocean, the magnitude of these fluxes is consistent with fluxes calculated based on the water-column distribution of most elements, and are equivalent to the global supply of these elements by rivers. The hydrothermally influenced sediment is a strong source of copper, zinc and cobalt up to three km from the vent due to oxidation of sulfide minerals. Close to the vents, the sediment is high in iron oxyhydroxides that adsorb the oxyanions vanadate, arsenate and phosphate, acting as a sink for these elements. The results of this study highlight the importance of red-clay sediment in shaping the chemical composition of the ocean, and suggest an important role for hydrothermally influenced sediment in modulating the contributions of hydrothermal vents to ocean biogeochemistry.
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