MITHO logo

Author: Jon White

New publication – Positive correlation between the Po River discharge and ocean colour trends of Chl and TSM in the Adriatic Sea

Posted on by Jon White

Positive correlation between the Po River discharge and ocean colour trends of Chl and TSM in the Adriatic Sea

Abstract

Coastal areas represent delicate and complex environments due to the interconnection between land and sea, where marine, fluvial and anthropogenic stressors combine threatening and undermining coastal health. Sea level rise and increasing storminess, for instance, lead to more frequent coastal flooding and habitat loss due to erosion; sediment supply by rivers, on the other hand, helps coastal areas to balance and restore habitat loss. However, excessive riverine nutrient inputs may lead to coastal eutrophication phenomena, putting coastal ecosystem as well as coastal communities at serious risk. Here, we compute high resolution (300 m) Chlorophyll-a (Chl) and Total Suspended Matter (TSM, a proxy for sediment concentration) trends over the Adriatic Sea by using the single sensors MERIS (from 2003 to 2012) and OLCI (from 2017–2024) data, to study the response of the marine ecosystem to human and/or environmental pressures, and thus for detecting coastal areas likely subject to eutrophication and/or sediment starvation. Such an analysis is complemented by Po River discharge data to investigate the role of river outputs in shaping the observed trends within the Adriatic basin. Our results reveal Chl and TSM trends in the northern part of the Adriatic basin being positively correlated with the Po River discharge during the investigated period, for both MERIS and OLCI data. Increases/decreases in the Po River outflow resulted in positive/negative Chl and TSM trends. Although a negative trend of Chl was documented within the Adriatic Sea in the last 25 years, Po River load fluctuations regulate long- and short-term, local trends of both Chl and TSM in the North Adriatic basin. This result suggests a direct relationship existing between river discharge and statistical trends of TSM and Chl in delta areas.

Read the full publication

Vona I, Colella S, Sammartino M, Brando VE and Falcini F (2025) Positive correlation between the Po River discharge and ocean colour trends of Chl and TSM in the Adriatic Sea. Front. Remote Sens. 6:1574347. doi: 10.3389/frsen.2025.1574347

New publication – Monitoring the Multiple Stages of Climate Tipping Systems from Space: Do the GCOS Essential Climate Variables Meet the Needs?

Posted on by Jon White

Monitoring the Multiple Stages of Climate Tipping Systems from Space: Do the GCOS Essential Climate Variables Meet the Needs?

Abstract

Many components of the Earth system feature self-reinforcing feedback processes that can potentially scale up a small initial change to a fundamental state change of the underlying system in a sometimes abrupt or irreversible manner beyond a critical threshold. Such tipping points can be found across a wide range of spatial and temporal scales and are expressed in very different observable variables. For example, early-warning signals of approaching critical transitions may manifest in localised spatial pattern formation of vegetation within years as observed for the Amazon rainforest. In contrast, the susceptibility of ice sheets to tipping dynamics can unfold at basin to sub-continental scales, over centuries to even millennia. Accordingly, to improve the understanding of the underlying processes, to capture present-day system states and to monitor early-warning signals, tipping point science relies on diverse data products. To that end, Earth observation has proven indispensable as it provides a broad range of data products with varying spatio-temporal scales and resolutions. Here we review the observable characteristics of selected potential climate tipping systems associated with the multiple stages of a tipping process: This includes i) gaining system and process understanding, ii) detecting early-warning signals for resilience loss when approaching potential tipping points and iii) monitoring progressing tipping dynamics across scales in space and time. By assessing how well the observational requirements are met by the Essential Climate Variables (ECVs) defined by the Global Climate Observing System (GCOS), we identify gaps in the portfolio and what is needed to better characterise potential candidate tipping elements. Gaps have been identified for the Amazon forest system (vegetation water content), permafrost (ground subsidence), Atlantic Meridional Overturning Circulation, AMOC (section mass, heat and fresh water transports and freshwater input from ice sheet edges) and ice sheets (e.g. surface melt). For many of the ECVs, issues in specifications have been identified. Of main concern are spatial resolution and missing variables, calling for an update of the ECVS or a separate, dedicated catalogue of tipping variables.

View the full publication

Loriani, S., Bartsch, A., Calamita, E. et al. Monitoring the Multiple Stages of Climate Tipping Systems from Space: Do the GCOS Essential Climate Variables Meet the Needs?. Surv Geophys (2025). https://doi.org/10.1007/s10712-024-09866-4

New publication – Extreme Events Contributing to Tipping Elements and Tipping Points

Posted on by Jon White

Extreme Events Contributing to Tipping Elements and Tipping Points

Abstract

This review article provides a synthesis and perspective on how weather and climate extreme events can play a role in influencing tipping elements and triggering tipping points in the Earth System. An example of a potential critical global tipping point, induced by climate extremes in an increasingly warmer climate, is Amazon rainforest dieback that could be driven by regional increases in droughts and exacerbated by fires, in addition to deforestation. A tipping element associated with the boreal forest might also be vulnerable to heat, drought and fire. An oceanic example is the potential collapse of the Atlantic meridional overturning circulation due to extreme variability in freshwater inputs, while marine heatwaves and high acidity extremes can lead to coral reef collapse. Extreme heat events may furthermore play an important role in ice sheet, glacier and permafrost stability. Regional severe extreme events could also lead to tipping in ecosystems, as well as in human systems, in response to climate drivers. However, substantial scientific uncertainty remains on mechanistic links between extreme events and tipping points. Earth observations are of high relevance to evaluate and constrain those links between extreme events and tipping elements, by determining conditions leading to delayed recovery with a potential for tipping in the atmosphere, on land, in vegetation, and in the ocean. In the subsurface ocean, there is a lack of consistent, synoptic and high frequency observations of changes in both ocean physics and biogeochemistry. This review article shows the importance of considering the interface between extreme events and tipping points, two topics usually addressed in isolation, and the need for continued monitoring to observe early warning signs and to evaluate Earth system response to extreme events as well as improving model skill in simulating extremes, compound extremes and tipping elements.

Read the full publication

Romanou, A., Hegerl, G.C., Seneviratne, S.I. et al. Extreme Events Contributing to Tipping Elements and Tipping Points. Surv Geophys (2024). https://doi.org/10.1007/s10712-024-09863-7

New publication – Opportunities for Earth Observation to Inform Risk Management for Ocean Tipping Points

Posted on by Jon White

Opportunities for Earth Observation to Inform Risk Management for Ocean Tipping Points

Abstract

As climate change continues, the likelihood of passing critical thresholds or tipping points increases. Hence, there is a need to advance the science for detecting such thresholds. In this paper, we assess the needs and opportunities for Earth Observation (EO, here understood to refer to satellite observations) to inform society in responding to the risks associated with ten potential large-scale ocean tipping elements: Atlantic Meridional Overturning Circulation; Atlantic Subpolar Gyre; Beaufort Gyre; Arctic halocline; Kuroshio Large Meander; deoxygenation; phytoplankton; zooplankton; higher level ecosystems (including fisheries); and marine biodiversity. We review current scientific understanding and identify specific EO and related modelling needs for each of these tipping elements. We draw out some generic points that apply across several of the elements. These common points include the importance of maintaining long-term, consistent time series; the need to combine EO data consistently with in situ data types (including subsurface), for example through data assimilation; and the need to reduce or work with current mismatches in resolution (in both directions) between climate models and EO datasets. Our analysis shows that developing EO, modelling and prediction systems together, with understanding of the strengths and limitations of each, provides many promising paths towards monitoring and early warning systems for tipping, and towards the development of the next generation of climate models.

View the full publication

Wood, R.A., Baker, J.A., Beaugrand, G. et al. Opportunities for Earth Observation to Inform Risk Management for Ocean Tipping Points. Surv Geophys (2024). https://doi.org/10.1007/s10712-024-09859-3

Teaching students about ocean colour

Posted on by Jon White
Student holding a mbile phone with specilist mount

MiTHO project participant Dr Victor Martinez-Vicente led the activities for the week, with a focus on introducing students to the use of ocean colour measured from satellites and how it is (in practice) related to the properties of water constituents.

The Plymouth coastal water was simulated with a 1000 litre tank, filled with water and sediments from the Plymouth Sound sea floor in the UK.

In this gallery of photos, you can see an experiment from the week where they simulated coastal water and their own “satellite”.

The “satellite” was a hyperspectral radiometer, which follows similar measurement principles to the real satellites under construction by the European Space Agency, ESA. They added different amounts of sediment to increase the turbidity (the relative clarity or cloudiness) of the water and measured the increased turbidity using the “model satellite”.

In the experiment, they also used measurements that anyone can use – citizen science tools – useful for monitoring the coast where satellites have blind spots (e.g. very close to land).

The students took high-tech citizen science smartphone camera measurements through the HydroColor App – which uses a phone’s digital camera to determine the reflectance of natural water bodies and also measurements with very ancient tools, such as the Secchi Disk.

Student using the smartphone to take measurements

A Secchi disk, historically called a “dinner plate” by sailors, is a simple water quality monitoring tool that has been used since the mid 19th Century. Secchi disks are used in the open ocean to measure water turbidity, they work by lowering the white disk into the water and recording the depth at which it disappears, and this tool is still useful to ocean scientists today, even in the age of satellites.

Dr Victor Martinez-Vicente shows the student the Secchi disk

The work links with the work of the MiTHO project but also the ESA-funded HyperBOOST projects, which involve monitoring marine ecosystem health and threats by using in-situ hyperspectral bio-optical and satellite measurements.