Survey strategies to quantify and optimize detecting probability of a CO2 seep in a varying marine environment

AbstractDesigning a marine monitoring program that detects CO2 leaks from subsea geological storage projects is challenging. The high variability of the environment may camouflage the anticipated anisotropic signal from a leak and there are a number of leak scenarios. Marine operations are also costly constraining the availability of measurements. A method based on heterogeneous leak scenarios and anisotropic predictions of chemical footprint under varying current conditions is presented. Through a cost function optimal placement of sensors can be given both for fixed installations and series of measurements during surveys. Ten fixed installations with an optimal layout is better than twenty placed successively at the locations with highest leakage probability. Hence, optimal localizations of installations offers cost reduction without compromising precision of a monitoring program, e.g. quantifying and reduce probabilities of false alarm under control. An optimal cruise plan for surveys, minimizing transit time and operational costs, can be achieved

Assessing Model Uncertainties Through Proper Experimental Design

This paper assesses how parameter uncertainties in the model for rise velocity of CO2 droplets in the ocean cause uncertainties in their rise and dissolution in marine waters. The parameter uncertainties in the rise velocity for both hydrate coated and hydrate free droplets are estimated from experiment data. Thereafter the rise velocity is coupled with a mass transfer model to simulate the fate of dissolution of a single droplet. The assessment shows that parameter uncertainties are highest for large droplets. However, it is also shown that in some circumstances varying the temperature gives significant change in rise distance of droplets.publishedVersio

Decadal trends in ocean acidification from the Ocean Weather Station M in the Norwegian Sea

The Ocean Weather Station M (OWSM) is situated at a fixed position in the Norwegian Sea, one of the major basins of the Nordic Seas, which represents an important area for uptake of atmospheric CO2 as well as deep water formation. At OWSM, the inorganic carbon cycle has been regularly monitored since 2001, and significant interannual changes of the carbonate system have been determined. Data collected at this site since the 1990s have been included, and over the 28 last years the surface fugacity of CO2 (fCO2) has increased by 2.92 ± 0.37 μatm/yr, while surface pH and aragonite saturation (ΩAr) have decreased by -0.0033 ± 0.0005/yr and -0.018 ± 0.003/yr, respectively. This corresponds to a surface pH change of -0.092 over 28 years, which is comparable to the global mean pH decrease of -0.1 since the onset of the industrial revolution. Our estimates suggest that 80% of the surface pH trend at OWSM is driven by uptake of CO2 from the atmosphere. In the deepest layer, ΩAr has decreased significantly (-0.006 ± 0.001/yr) over the last 28 years, now occasionally reaching undersaturated values (ΩAr < 1). As a rough estimate, the saturation horizon has shoaled by 7 m/yr between 1994 and 2021. The increase in surface fCO2 is confirmed by semi-continuous measurements of CO2 from the site (2.69 ± 0.14 μatm/yr), and thus, the area has become less of a net sink for atmospheric CO2, taking into consideration an atmospheric CO2 increase at OWSM of 2.27 ± 0.08 μatm/yr.publishedVersio

PVTx Properties of a Two-phase CO2 Jet from Ruptured Pipeline

Span and Wagner equation of state (SW EOS) have been used to investigate changes in the thermodynamic properties of CO2 during a depressurization process from a pipeline into marine environment. The process is assumed to be isenthalpic, as only the thermodynamic change at the moment of depressurization is considered. The calculations show that the depth location of the pipeline influences greatly the density, temperature and volume changes, because of the difference in the surrounding pressures. In general the two-phase area is reached at depths shallower than 600 meters, which yields for the Norwegian Continental Shelf, as it is mainly shallower than 500 meters depth. There is a rapid decrease in density in the two-phase area causing a rapid expansion in the volume of CO2 from 4 MPa to 1 MPa. At the shallowest depth considered (100m) the volume fraction consist almost entirely of gas, and the density change give a significant increase in volume.publishedVersio

The Nordic Seas carbon budget: Sources, sinks, and uncertainties

A carbon budget for the Nordic Seas is derived by combining recent inorganic carbon data from the CARINA database with relevant volume transports. Values of organic carbon in the Nordic Seas' water masses, the amount of carbon input from river runoff, and the removal through sediment burial are taken from the literature. The largest source of carbon to the Nordic Seas is the Atlantic Water that enters the area across the Greenland-Scotland Ridge; this is in particular true for the anthropogenic CO2. The dense overflows into the deep North Atlantic are the main sinks of carbon from the Nordic Seas. The budget show that presently 12.3 ± 1.4 Gt C yr−1 is transported into the Nordic Seas and that 12.5 ± 0.9 Gt C yr−1 is transported out, resulting in a net advective carbon transport out of the Nordic Seas of 0.17 ± 0.06 Gt C yr−1. Taking storage into account, this implies a net air-to-sea CO2 transfer of 0.19 ± 0.06 Gt C yr−1 into the Nordic Seas. The horizontal transport of carbon through the Nordic Seas is thus approximately two orders of magnitude larger than the CO2 uptake from the atmosphere. No difference in CO2 uptake was found between 2002 and the preindustrial period, but the net advective export of carbon from the Nordic Seas is smaller at present due to the accumulation of anthropogenic CO2

Layout of CCS monitoring infrastructure with highest probability of detecting a footprint of a CO2 leak in a varying marine environment

Monitoring of the marine environment for indications of a leak, or precursors of a leak, will be an intrinsic part of any subsea CO2 storage projects. A real challenge will be quantification of the probability of a given monitoring program to detect a leak and to design the program accordingly. The task complicates by the number of pathways to the surface, difficulties to estimate probabilities of leaks and fluxes, and predicting the fluctuating footprint of a leak. The objective is to present a procedure for optimizing the layout of a fixed array of chemical sensors on the seafloor, using the probability of detecting a leak as metric. A synthetic map from the North Sea is used as a basis for probable leakage points, while the spatial footprint is based on results from a General Circulation Model. Compared to an equally spaced array the probability of detecting a leak can be nearly doubled by an optimal placement of the available sensors. It is not necessarily best to place the first in the location of the highest probable leakage point, one sensor can monitor several potential leakage points. The need for a thorough baseline in order to reduce the detection threshold is shown.publishedVersio

Direct measurements of CO2 flux in the Greenland Sea

During summer 2006 eddy correlation CO2 fluxes were measured in the Greenland Sea using a novel system set-up with two shrouded LICOR-7500 detectors. One detector was used exclusively to determine, and allow the removal of, the bias on CO2 fluxes due to sensor motion. A recently published correction method for the CO2-H2O cross-correlation was applied to the data set. We show that even with shrouded sensors the data require significant correction due to this cross-correlation. This correction adjusts the average CO2 flux by an order of magnitude from -6.7 x 10⁻² mol m⁻² day⁻¹ to -0.61 x 10⁻² mol m⁻² day⁻¹, making the corrected fluxes comparable to those calculated using established parameterizations for transfer velocity

Tilførselsprogrammet 2011. Overvåking av forsuring av norske farvann

Denne rapporten gjelder undersøkelser av havforsuring som er utført av IMR, NIVA og BCCR i oppdrag fra Klif i 2011. Den er basert på målinger mellom Bergen-Kirknes og Tromsø-Longyearbyen utført av NIVA. Prøvetaking av vertikalen fra Torungen-Hirtshals, Svinøy-NW, Gimsøy-NW og Fugløya-Bjørnøya er utført av IMR. Resultatene fra Norskehavet viser en klar sesongvariasjon i øvre 100 m av vannsøylen, som for det meste er styrt av styrken på primærproduksjonen. I tillegg påvirkes karboninnholdet av kystvannet som brer seg vestover i løpet av sommeren. Metningsgraden for aragonitt (Ar) er mellom 1.95 til 1.6 på 300 m dyp. I Norskehavet befinner =1.6 seg på 500 m dyp, og i Nordsjøen på ca 200 m. I Norskehavet er det undermetning fra like under 1500 meters dyp av aragonitt og overmetning av kalsitt i hele vannsøylen. I Barentshavet lå Ar mellom 1.07-2.62 med min. verdier i kystområdet mellom Kirkenes og Tromsø i januar (1.07-2.03), mens Ar var 1.49-2.52 i desember, og karakterisert av en stor variasjon fra 1.67 til 2.62 som skyldes en økt biologisk produksjon. Historiske data er sammenlignet på Havforskningens hydrografiske seksjoner i 2011 og CARINA databasen. Primært ble data fra 1997-2011 i nord-vestlig retning fra Gimsøy og Svinøy benyttet for å studere trender i Norskehavet, men analysen omfatter også data fra Barentshavet. Trender viser en økning av karbonkonsentrasjonene målt i 2011 relativt til historiske data. Dette gjenspeiler hovedsakelig havets opptak av menneskeskapt CO2. Konklusjonen er at de fleste områder studert i denne rapporten er mettet i forhold til kalsitt, og undermetning av aragonitt viser seg på 1500 meters dyp i Norskehavet.Kli

Toward a Comprehensive and Integrated Strategy of the European Marine Research Infrastructures for Ocean Observations

Research Infrastructures (RIs) are large-scale facilities encompassing instruments, resources, data and services used by the scientific community to conduct high-level research in their respective fields. The development and integration of marine environmental RIs as European Research Vessel Operators [ERVO] (2020) is the response of the European Commission (EC) to global marine challenges through research, technological development and innovation. These infrastructures (EMSO ERIC, Euro-Argo ERIC, ICOS-ERIC Marine, LifeWatch ERIC, and EMBRC-ERIC) include specialized vessels, fixed-point monitoring systems, Lagrangian floats, test facilities, genomics observatories, bio-sensing, and Virtual Research Environments (VREs), among others. Marine ecosystems are vital for life on Earth. Global climate change is progressing rapidly, and geo-hazards, such as earthquakes, volcanic eruptions, and tsunamis, cause large losses of human life and have massive worldwide socio-economic impacts. Enhancing our marine environmental monitoring and prediction capabilities will increase our ability to respond adequately to major challenges and efficiently. Collaboration among European marine RIs aligns with and has contributed to the OceanObs’19 Conference statement and the objectives of the UN Decade of Ocean Science for Sustainable Development (2021–2030). This collaboration actively participates and supports concrete actions to increase the quality and quantity of more integrated and sustained observations in the ocean worldwide. From an innovation perspective, the next decade will increasingly count on marine RIs to support the development of new technologies and their validation in the field, increasing market uptake and produce a shift in observing capabilities and strategies.Peer reviewe