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X-EBUS: Extreme Ocean Weather Events and their Role for Ocean Biogeochemistry and Ecosystems in Eastern Boundary Upwelling Systems

Applicant Gruber Nicolas
Number 175787
Funding scheme Project funding (Div. I-III)
Research institution Institut für Biogeochemie und Schadstoffdynamik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Oceanography
Start/End 01.09.2018 - 31.08.2022
Approved amount 800'000.00
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All Disciplines (2)

Discipline
Oceanography
Other disciplines of Environmental Sciences

Keywords (14)

Extreme Events; Regional Oceanic Modeling System (ROMS); Ocean Acidification; Ocean lower trophic level ecosystems; Ocean Warming; Ocean nitrogen cycle; Ocean carbon cycle; Ocean Biogeochemistry; Regional Weather Model COSMO; Eastern Boundary Upwelling Systems; Ocean Deoxygenation; Humboldt Current System; Regional Earth System Model; California Current System

Lay Summary (German)

Lead
Klimatische Extremereignisse haben oft einen grösseren Einfluss auf Ökosysteme als der langsam fortschreitende Klimawandel. Trotz dessen ist das jetzige Verständnis von Extremereignissen eher dürftig, insbesondere wenn es um solche Ereignisse in den Weltmeeren geht. Die bisher am besten untersuchten Extremereignisse sind marine Hitzewellen, d.h. Situationen wo die Meerestemperatur während Tagen bis Wochen weit oberhalb der Norm liegt. Diese führen, z.B., zur Ausbleichung von Korallenriffen und Verändern die Artenzusammensetzung im Ozean. Auch sehr relevant, aber bisher nicht untersucht, sind Extremereignisse im Zusammenhang mit der Ansäuerung der Meere und dem Verlust von Sauerstoff, d.h. die Bildung von sogenannten „Todeszonen“.
Lay summary
Inhalt und Ziel:

Das übergeordnete Ziel unserer Forschung ist es, solche marine Extremereignisse zu untersuchen und zu bestimmen, wie oft sie vorkommen und wie stark sie sind. Unser besonderes Augenmerk liegt auf dem Verständnis der Bedingungen, unter welchen solche Ereignisse entstehen, und wie sie sich auf biogeochemische Kreisläufe und Ökosysteme auswirken. Desweiteren wollen wir wissen inwiefern sich solche Extremereignisse schon geändert haben, und wie sie sich in der Zukunft möglicherweise entwickeln werden. Zum Erreichen unserer Ziele verwenden wir Beobachtungen und numerische Modelle, die die komplexen Wechselwirkungen zwischen der Atmosphäre, dem Ozean, und den biogeochemischen Prozessen abbilden. Wir fokussieren uns auf die Auftriebsgebiete im Pazifik vor den Küsten von Nord- und Südamerika, wo solche Extremereignisse verstärkt vorkommen.

Wissenschaftlicher und gesellschaftlicher Kontext:

Der menschgemachte Klimawandel ist mir grosser Wahrscheinlichkeit ein wichtiger Treiber für die Entstehung von marinen Extremereignissen. Es ist deshalb wichtig besser zu verstehen, wie sich diese Ereignisse im Zusammenhang mit dem Klimawandel entwickeln werden, und welche Ereignisse sich mit einer starken Absenkung der CO2 Emissionen verhindern lassen. 
 

Direct link to Lay Summary Last update: 17.07.2018

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
153452 SOGate: Phytoplankton ecosystem control of the Southern Ocean biogeochemical gate 01.09.2014 Project funding (Div. I-III)
149384 CALNEX: Quantifying the exchange of carbon and nutrients between the coastal and open seas: A comparative modeling study of the California and Canary Current Systems 01.02.2014 Project funding (Div. I-III)

Abstract

Extreme events on land are known to shape the structure of ecosystems and substantially affect their biogeochemical activity. But our understanding of the role of such events in the marine realm is very poor, especially for those associated with the marine stressors ocean warming, ocean acidification, and loss of oxygen. Given our expectation of the ocean to continue to warm and acidify, these extreme events very likely will become more frequent and intense in the future. Even though it is well understood that such events are the result of the interaction of ocean and atmosphere weather, we know presently very little about their characteristics and how they will impact marine ecosystems and ocean biogeochemistry. Regions of particular concern are the eastern boundary upwelling systems (EBUS) and especially the California and Humboldt Current Systems, as these highly productive ecosystems are known to be very susceptible to the joint effects of all stressors. Both systems are already today exposed to waters with very low pH and saturation states with regard to mineral CaCO3 and are underlain by waters containing very little to no oxygen. Thus, extreme weather can very quickly move these systems into conditions that are far outside the tolerable range for many organisms and initiate strong and potentially non-linear and possibly irreversible biogeochemical responses.Here, I propose to address the role of extreme ocean weather events associated with warming, ocean acidification and oxygen loss in these two EBUS by determining (i) the distribution and intensity of such events in the past, present and future, (ii) the processes governing these events and their return periods, (iii) the potential impact of these events on marine lower trophic level ecosystems and (iv) how these impacts feed back to the ocean's biogeochemical cycles. These objectives will be addressed by a model-based approach augmented with the analysis and interpretation of in-situ and remote sensing-based observations. The core tool we will employ is a high-resolution Regional Earth System Model (R-ESM) consisting of the regional atmospheric model COSMO coupled to the Regional Oceanic Modeling System (ROMS). The latter includes the Biogeochemical Elemental Cycling (BEC) model that we will extend to include a better representation of the sensitivity of key ecological processes to changes in temperature, oxygen and ocean acidification. This R-ESM will be configured for both the California and Humboldt Current Systems, and will be driven by reanalysis products (20th century to present) and outputs from global ESMs (future). Thanks to its kilometer-scale resolution, our R-ESM will simulate the oceanic weather and the associated extreme events with much higher fidelity than can be achieved with a global ESM, permitting us to assess the characteristics of these events with regard to their intensities, duration, severity, and return periods in an unprecedented manner. Of particular interest is the interaction between the highly dynamic structure of the multiple stressors in time and space with the dynamics of the ecosystems and the ocean's biogeochemical cycles. Key hypotheses we will investigate include (i) extreme events become more frequent and intense in a warmer, high CO2 ocean, (ii) these more frequent extreme events alter the lower trophic community structure, leading to a reduction of productivity owing to higher nutrient losses from the upwelling system, and (iii) these changes feedback to ocean biogeochemistry by increasing the loss of CO2 to the atmosphere and further increasing nutrient loss due to extreme event-induced enhanced denitrification.
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