Long title : Alexey Fedorov : The response of tropical Pacific mean state and ENSO to global warming
Resume : Alexey Fedorov (LOCEAN and Yale University) : The response of tropical Pacific mean state and ENSO to global warming.
Description :
The response of the tropical Pacific to rising atmospheric CO2 concentrations remains uncertain. In particular, the projected development of the eastern equatorial Pacific warming pattern, and the associated weakening of the Walker circulation, contracts the strengthening of the Walker cell that has been observed during the past 30-40 years. Here we discuss the key mechanisms that shape ongoing and future changes in the tropical Pacific on different timescales, including the role of ocean thermostat competing with the eastern equatorial Pacific warming. We also discuss the robust strengthening of ENSO predicted in a broad range of realistic and idealized global warming experiments and across different models within the CMIP6 archive.
begin date : 04/07/2022
info date :
Mon Jul 04 2022 15:00:00
place: Sorbonne Université LOCEAN Couloir 45-55 4e étage pièce 417
contact :
Long title : Phytoplankton community response to atmospheric dust addition in the Arabian Sea under different CO2 levels: An experimental Approach.
Resume : Haimanti BISWAS (National Institute of Oceanography – CSIR, Goa, India): Phytoplankton community response to atmospheric dust addition in the Arabian Sea under different CO2 levels: An experimental Approach.
Description :
The Indian Ocean receives nearly one-fourth of the global atmospheric dust deposition which is about 113 Mt. yr− 1 and the Arabian Sea is vulnerable to dust supply which can potentially modulate its surface water biogeochemical processes, particularly, phytoplankton communities. Importantly, the steady increase in Sea Surface Temperature (SST) of the Arabian Sea may intensify oligotrophy escalating the role of atmospheric dust for phytoplankton growth and community composition. Furthermore, the Arabian Sea is a natural source of atmospheric CO2 and with increasing atmospheric CO2 levels, the surface ocean may experience decreasing pH. There are studies based on satellite based measurement of dust plumes and corresponding enhancement in Chla as well as model based observations, highlighting the role of dust input on phytoplankton production from the Arabian Sea. But there was no experimental study showing how dust addition my impact the phytoplankton community in natural population. This study documented for the first time the impacts of atmospheric dust input under the simulated ocean acidification scenario on the natural phytoplankton communities from the Arabian Sea during winter monsoon. The results show that dust addition increased phytoplankton biomass (cell density and Chla) and community composition. The inputs of inorganic nitrogen and iron from dusts were likely to be the key growth-promoting factors that increased the relative contribution of micro and nanophytoplankton irrespective of the CO2 levels, whereas picophytoplankton decreased. The predominance of pennate diatoms and non-diatoms was mostly due to low dissolved silicate (DSi) availability. The cell density of the pennate diatoms Pseudo-nitzschia sp., Nitzschia sp., and Cylindrotheca closterium increased by several orders of magnitude in response to dust addition under high CO2 levels. The dinoflagellates, Alexandrium sp., and Gymnodinium sp. showed higher tolerance to high CO2 and proliferated in response to dust input. The present experimental conditions can be compared to the future ocean scenario (low DSi, OA, and dust input) where the proliferation of non-palatable/ toxigenic phytoplankton taxa may be expected which has the potential to impact ecological processes like trophic transfer, carbon cycling, and fisheries.
begin date : 28/06/2023
info date :
Date & Time: Wed Jun 28 2023 11:00:00 GMT+0200 (Central European Summer Time)
Room: salle du LOCEAN, couloir 45-55, 4ème étage, pièce 417
place: Sorbonne Université LOCEAN Couloir 45-55 4e étage pièce 417
contact : damien.cardinal@locean.ipsl.fr
Long title : Toward model consistent initialization of decadal climate predictions
Resume : Iuliia Polkova (Univ. Hambourg) : Presentation covers initialization of climate predictions in general.
Description :
Speaker: Iuliia Polkova (Univ. Hambourg)
Presentation covers initialization of climate predictions in general.
I will try not to bore audience with the analyses of skills or
mechanisms for predictability, though the presentation relies on such
in already published papers. Instead… it would be interesting to
have an interactive conversation on initialization, even though it
might not be everyone’s topic, and to talk about challenges of this
field of research and maybe identify interesting directions also with
input from the audience. As a teaser for discussion, I have collected
some ideas behind different initialization and assimilation methods
for decadal predictions and my speculations why they fulfilled or not
fulfilled the expectations of their developers. I also mention
whether uninitialized predictions can replace initialized predictions
and speculate about what we can try to learn from simpler climate
models in terms of initialization and data assimilation. I suppose the
presentation would be of interest for prediction system developers but
hopefully not only. If someone wants to know how observations enter
prediction systems and implications of this for the quality of
predictions, they should drop by. Hopefully, we can have interesting
discussions.
begin date : 20/04/2022
info date :
Please note this seminar has been postponed to: Wed Apr 20, 14:00, Salle 417
Ce séminaire a été reporté au : Mercredi 20 avril, 14:00, Salle 417
place: Sorbonne Université LOCEAN Couloir 45-55 4e étage pièce 417
contact :
Long title : The evolution of the Atlantic Meridional Overturning Circulation from Decades to Millenia
Resume : Levke Caesar (University of Maynooth): The evolution of the Atlantic Meridional Overturning Circulation from Decades to Millenia.
Description :
Speaker : Levke Caesar (University of Maynooth)
The Atlantic Meridional Overturning Circulation (AMOC), one of
Earth’s major ocean circulation systems, redistributes heat on our planet and has a major impact on climate. Its past and future strength are therefore of major interest, but the system is not easily measured. In my presentation I will present a consistent picture of the evolution of the AMOC over different time scales and from different sources: From the about 15 years of direct continuous observational data, over reanalysis products and ship measurements to temperature and ocean sediment proxy data. The overview shows that while the AMOC displays a large amount of natural variability over the different time scales, its behaviour over the last one to two hundred years is unprecedented compared to the last 1,600 years and it is fairly certain that the AMOC over the last decades has been weaker than ever before in that time period.
begin date : 10/05/2022
info date :
Tue May 10 2022 11:00:00 GMT+0200 (Central European Summer Time)
Room: IPSL Salle 201 Tour 44/45 2eme étage
place: Salle visioconférence IPSL, Tour 45-55, 2ème étage, Université Pierre et Marie Curie, 4 place Jussieu, 75005 Paris
contact :
Long title : A biological oceanographer's perspective on understanding future ocean states
Resume : Mark Ohman: A biological oceanographer’s perspective on understanding future ocean states
Description :
Ecological responses to climate change and climate
variability are often difficult to predict because of nonlinearities
in biotic responses. This presents the need for close integration of
process-oriented experimental investigations with long term time
series measurements and modeling studies. I will illustrate an
approach we have taken in the Northeast Pacific, integrating the
California Current Ecosystem Long-Term Ecological Research (CCE-LTER)
site with the remarkable CalCOFI time series. I will also show the
merits of breaking open the « black boxes » of N, P, and Z, which are
classically represented in models by one or a limited number of
biological compartments. The appropriate level of biological
granularity is highly dependent upon the question asked and the
physical scales considered. The seminar will also briefly introduce
the Zooglider. This is a novel autonomous instrument we have
developed that is particularly well suited to resolving fine scale
ocean phenomema, which are increasingly recognized as consequential
for ocean ecology and biogeochemistry.
begin date : 24/10/2023
info date :
Date & Room: mardi 24 octobre à 11h, salle du LOCEAN, couloir 45-55, 4ème étage, pièce 417
place: Sorbonne Université LOCEAN Couloir 45-55 4e étage pièce 417
contact : sara.labrousse@locean.ipsl.fr
Long title : Emergence of Changes in the El Niño Southern Oscillation and Teleconnection Patterns
Resume : Mat Collins (University of Exeter): Emergence of Changes in the El Niño Southern Oscillation and Teleconnection Patterns
Description :
Future changes in the mean climate of the tropical Pacific
and characteristics of the El Niño Southern Oscillation (ENSO) are
established as being likely. In this work we determine the time of
emergence of climate change signals from the background natural
variability. We find that the annual-mean sea surface temperature
(SST) signal across the whole tropical Pacific has already emerged,
but appears latest in the east, where the background noise is high.
The signal of a wetter annual-mean rainfall in the east Pacific is
expected to emerge by mid-century, with some sensitivity to emission
scenario. However, the signal of ENSO-related rainfall variability is
projected to emerge by about 2040 regardless of the emission scenario
followed. This is about 30 years earlier than ENSO-related SST
variability signal. These results are discussed in the light of recent
observed trends in SSTs in the tropical Pacific. We also discuss
changes in ENSO teleconnection patterns, i.e. the way that ENSO
impacts climate around the world.
begin date : 19/06/2023
info date :
Date & Time: Mon Jun 19 2023 16:00:00 GMT+0200 (Central European Summer Time)
Room: salle du LOCEAN, couloir 45-55, 4ème étage, pièce 417
place: Sorbonne Université LOCEAN Couloir 45-55 4e étage pièce 417
contact : Eric.Guilyardi@locean.ipsl.fr
Long title : Raisa Siqueira (BOREA) : pCO2 seasonal and spatial variability in a large mangrove-dominated delta
Resume : Raisa Siqueira (BOREA): pCO2 seasonal and spatial variability in a large mangrove-dominated delta
Description :
Speaker : Raisa Siqueira (BOREA)
Tropical estuarine systems are a key component in the transport of carbon to the open ocean and important sources of carbon dioxide (CO2) to the atmosphere. However, many large tropical estuaries are still unaccounted for regarding their carbon dynamics and, particularly, their water-atmosphere CO2 fluxes. In this study, we aimed to understand the seasonal and spatial variability of aquatic partial pressure of CO2 (pCO2) and water-atmosphere CO2 fluxes in the Parnaíba River Delta, the largest coastal delta in the Americas. This tropical delta is a pristine environment dominated by dense mangrove forests located on a climatic transitional coast, between humid and semi-arid climates, with marked seasonality in rainfall and river discharge. Continuous measurements of pCO2, temperature, salinity, and wind velocity were taken, while subsurface water samples were collected in discrete stations to analyze for pH, total alkalinity, dissolved inorganic carbon, dissolved oxygen, and chlorophyll-a. Our results indicated significant seasonal and spatial variability of pCO2 in the delta. The seasonal variability was mostly related to the intensity of the river discharge, while the high spatial variability indicated that the pCO2 is likely controlled by a combination of river and ocean water mixing, and biological processes (respiration and photosynthesis), in both seasons. The delta was a source of CO2, with averaged fluxes higher during the rainy season. Our results suggest that large tropical river deltas surrounded by extensive mangrove forests are important sources do CO2 to the atmosphere and that the seasonal variability of fluxes is important in the estimation of the annual contribution of CO2 by this type of system.
begin date : 21/06/2022
info date :
Date & Time: Tue June 21 2022 11:00
Location: IPSL Salle 201 Tour 44/45 2eme étage, https://zoom.us/j/94911316881?pwd=U1N3cEt0MStsVFFUM1c3cHFHYnNMQT09
place: IPSL, salle 201, 2e étage Tour 45-55, Sorbonne Universités, Campus Jussieu
contact : bruno.turcq@locean.ipsl.fr
Long title : Sr and Ca isotopic variability in the Bay of Bengal and the Godavari River, India
Resume : Ramananda Chakrabarti (Centre for Earth Sciences, Indian Institute of Science, Bengaluru): Sr and Ca isotopic variability in the Bay of Bengal and the Godavari River, India
Description :
Speaker : Ramananda Chakrabarti (Centre for Earth Sciences, Indian Institute of Science, Bengaluru)
In the first part of this talk, I will present Ca and Sr isotopic data for depth-bound samples from the Bay of Bengal. In the second part of this talk I’ll present seasonal variability in the geochemical and isotopic compositions of the basalt-draining portion of the Godavari River in peninsular India which drains into the Bay of Bengal. The results have implications for submarine groundwater discharge, carbonate precipitation, and silicate weathering.
begin date : 24/05/2022
info date :
Date & Time: Tue May 24 2022 11:00:00 GMT+0200 (Central European Summer Time)
Room: Salle de Conférence UFR TEB 46-56 2ème étage,
https://zoom.us/j/94498329182?pwd=djdxSlJhSEo0elhoOUZ2V0NtRHRPQT09
place: Salle de l'UFR TEB, Terre-Environnement-Biodiversité, Tour 46-56, 2e étage, Université Pierre et Marie Curie, 4 place Jussieu, 75005 Paris
contact : damien.cardinal@locean.ipsl.fr
Long title : Biases in coupled models on Indian Ocean Climate
Resume : Sebastian McKenna (University of New South Wales): Biases in coupled models on Indian Ocean Climate
Description :
Coupled climate models such as those in the Coupled Model
Intercomparison Project Phase 6 (CMIP6) suffer from biases in sea
surface temperature (SST) which affect the representation of impactful
climate phenomena. We investigate the surface layer heat budget to
diagnose the processes leading to monthly climatological SST biases in
historical simulation of 20 CMIP6 models. Our findings indicate that
SST biases are closely linked to biases in surface winds, although the
mechanisms leading to these biases vary across different regions. In
the west tropical Indian Ocean, weaker than observed winds reduce
surface currents which lead to warm SST biases. Over the Arabian Sea,
overly strong surface winds contribute to strong latent heat loss and
cool SST biases. In In the southeast tropical Indian Ocean, a cool
bias is likely caused by stronger winds, which drive higher levels of
offshore heat transport and upwelling compared to observations. These
relationships are consistent across models, shown by intermodel
relationships across different variables, which help to explain biases
in SST.
Previous works showed Pacific Ocean SST impacts the strength of Indian
Ocean variability in climate models, indicating that SST bias may
affect interannual variability. To explore the effect of removing SST
biases in the tropical Pacific Ocean, we conduct SST restoring
experiments using the coupled ACCESS-CM2 model. Initial results
indicate that restoring to observed climatology (no interannual
variability) reduces Indian Ocean SST relative to the control,
particularly around the maritime continent. We aim to find what impact
Pacific Ocean SST biases have on both seasonal cycle and interannual
variability of the Indian ocean.
begin date : 21/06/2023
info date :
Date & Time: Wed Jun 21 2023 11:00:00 GMT+0200 (Central European Summer Time)
Room: salle du LOCEAN, couloir 45-55, 4ème étage, pièce 417
place: Sorbonne Université LOCEAN Couloir 45-55 4e étage pièce 417
contact : pascal.terray@locean.ipsl.fr
Long title : The art of climate model evaluation: example of ENSO
Resume : Yann Planton (NOAA): The art of climate model evaluation: example of ENSO
Description :
Climate models help us understand the complexity of Earth’s climate, forecast the next seasons and predict the influence of anthropogenic forcings. It is therefore important to evaluate the performance of these models relative to observational datasets, to build confidence and to improve them.<br>Recently multiple ‘initial-condition large ensembles (LEs)’ have been computed to isolate the role of internal variability (natural variability arising from processes intrinsic to the coupled ocean–atmosphere–land–biosphere–cryosphere system). These LEs are particularly useful for the evaluation of modes of climate variability.
In this presentation I will discuss the art of climate model evaluation, using the example of El Niño–Southern Oscillation (ENSO). I will illustrate how internal variability affects ENSO evaluation and how LEs allow us to estimate the precision of the evaluation, which is necessary to decide on a new model version among multiple candidates. To deepen the discussion on the art of model evaluation, I will then illustrate the importance of choosing the right observational datasets for the right applications when evaluating and developing climate models.
begin date : 18/07/2023
info date :
Date & Time: Tue Jul 18 2023 11:00:00 GMT+0200 (Central European Summer Time)
Room: salle du LOCEAN, couloir 45-55, 4ème étage, pièce 417
place: Sorbonne Université LOCEAN Couloir 45-55 4e étage pièce 417
contact : Eric.Guilyardi@locean.ipsl.fr
Long title : Séminaire des doctorants du LOCEAN
Resume : Local drivers of marine heatwaves: A global analysis with an Earth System Model (Linus Vogt) & Linear Vorticity Balance validity and 3D vertical velocity reconstruction over the North Atlantic Ocean using OGCM climatology (Diego Cortes-Morales).
Description :
Linus Vogt – Local drivers of marine heatwaves: A global analysis with an Earth System Model. Marine heatwaves (MHWs) are periods of extreme warm ocean temperatures that can have devastating impacts on marine organisms and socio-economic systems. Despite recent advances in understanding the underlying processes of individual events, a global view of the local oceanic and atmospheric drivers of MHWs is currently missing. Here, we use daily-mean output of temperature tendency terms from a comprehensive fully coupled Earth system model to quantify the main local processes leading to the onset and decline of MHWs in the surface ocean. Our analysis reveals that net ocean heat uptake associated with more shortwave heat absorption and less latent heat loss is the primary driver of the onset of MHWs in the subtropics and mid-to-high latitudes. Reduced convective vertical mixing from the nonlocal portion of the KPP boundary layer scheme partially dampens the temperature increase. In contrast, ocean heat uptake is reduced during MHW onset in the tropics, where reduced vertical local mixing and diffusion cause the warming. In the subsequent decline phase, ocean heat loss to the atmosphere dominates the temperature decrease globally. The vertical local mixing process exhibits large seasonal variations, driving onset globally only during summer. Different types of MHWs with distinct driver combinations are identified within the large variability among events. Our analysis contributes to a better understanding of MHW drivers and processes and may therefore help to improve the prediction of high-impact marine heatwaves.
Diego Cortes-Morales- Linear Vorticity Balance validity and 3D vertical velocity reconstruction over the North Atlantic Ocean using OGCM climatology.
Ocean vertical velocities are several orders of magnitude smaller than the horizontal velocity field when looking at patterns larger than the sub-mesoscales, and for this reason, direct measurement in the ocean has not yet been possible. One method for estimating vertical velocity (w) field in the ocean interior is through a theoretical approach using more easily measured variables. The total Linear Vorticity Balance (TLVB: β(v_g+v_a)=f∂w/∂z) is tested in 56yr climatology from an eddy permitting OGCM to find out to what extent it explains the large-scale circulation in the North Atlantic basin and can be used to reconstruct the climatological w field. In the first part, we present a baroclinic analysis of the climatological TLVB. We find that it holds to first order within the thermocline (below the Mixed Layer), intermediate and bottom subtropical ocean when considered at spatial scales greater than approximately 7º at open ocean and 1º near the coast. Within western boundary currents, the equatorial band, and the subpolar gyre significant departures occur due to the importance of other terms in the vorticity budget such as nonlinearities or friction. We revisit the classical Sverdrup explanation of gyre dynamics by adding a baroclinic analysis of the North Atlantic thermocline major currents and water masses. In the second part, these results allow us to reconstruct w from the meridional velocity field to conclude with a discussion of similarities and discrepancies with two other existing estimates of w (one Omega Equation derived product and an ocean
reanalysis).
begin date : 15/03/2022
info date :
Tue Mar 15 2022 11:00:00 GMT+0100 (Central European Standard Time)
Room: Salle de l’UFR TEB, Tour 46/56 2ème étage
link: https://us02web.zoom.us/j/82793115215?pwd=QVIwMXVGeDVVNzZaLzN4WlRVWTRJdz09
place: Sorbonne Université LOCEAN Couloir 45-55 4e étage pièce 417
contact : lester.morgan-kwiatkowski@locean.ipsl.fr