Rising water can be caused by both sea level rise and subsidence of the Earth's surface. The combination of these two factors compose the "relative rise in sea level".
The rise in sea level is expected to significantly contribute to the impact of coastal hazards. Potential impacts are expected to be significant. Land subsidence can increase flood risk in low-altitude areas, which in turn has significant consequences (economic, environmental as well as human health impacts), inject of salty water, change wetlands and coastal ecosystems, and damage to infrastructure and historical monuments. These impacts are increased due to population growth and urbanization. The impact depends not only on the intensity and extent of coastal changes, but also on human response and adaptability to hazards. Due to the fact that land subsidence contributes to the relative rise in sea level, it is important to understand why, where and with which rate the event occurs, both in the present and in the future.
Over the last few years, the technique of interferometry from radar satellites has proven to be a powerful tool for the detection and measurement of Earth's ground deformation.
Multitemporal SAR interferometry is exploited to measure the deformation rate in the Delta of Evros and the city of Alexandroupolis (Fig. 1) in Greece for the years 1992 to date using the full archive of ERS, ASAR/ENVISAT and SENTINEL-1 acquisitions. The study areas are urban and rural, respectively, thus both relative techniques Persistent Scatterers interferometry and Small Baseline Subset as well as their combination are calculated (using STaMPS/MTI software).
The results of the mutlitemporal interferometry are combined with the change in sea level from altimetry measurements, derived from ASAR/ENVISAT mission as well as with morphological and land cover data.
The aim of the relative study is the contribution to the assessment of the relative hazard. Moreover it feeds a scenario of future relative sea level rise mapping for the purpose of spatio-temporal assessment of vulnerability of coastal areas leading to the effective management of coastal areas for the purpose of adaptation, increasing of the resilience and minimizing impacts.
Based on the particular physiographic features and bibliographic data, the coastal area in Northern Greece, including the city of Alexandroupolis and the Evros transboundary Delta (Fig.1), was selected as pilot area.
This study co-financed by the European Union (European Social Fund – ESF) and Greek national funds through the Sectoral Operational Program "Human Resources Development, Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF).

Lake ecosystems have a long history of disturbance, most prominently eutrophication from anthropogenic nutrient loading, and runoff regime alteration and desiccation due to hydro-engineering interventions. Both drivers imply spatially explicit downstream effects. In contrast, climate change effects occur globally and independently of anthropogenic watershed disturbances. To generate an understanding of the effects of these environmental changes, and to understand the responses of lakes worldwide as part of the Earth system, we need to integrate satellite Earth observations with existing biological and physical concepts. Accordingly, new approaches and updated requirements are needed where the upscaling of known concepts exceeds current capabilities of spaceborne remote sensing.

Since May 2018, the Copernicus Global Land Service (C-GLOPS) made available water quality, quantity and temperature data for lakes worldwide, based on the latest Sentinel satellites as well as 10 years of historical ENVISAT observations. For many lakes, this data represents the first continuous biophysical record available to a larger scientific community, allowing for the first spatially unbiased studies of ecosystem service and resilience assessment at a global scale. Available parameters to date include lake surface water temperature, turbidity, preliminary productivity indicators, water extent and level (large lakes only). We provide a preliminary review of selected parameters, and a comparison with theoretical expectations (Scheffer et al., 2009).

Global lake surface water temperature has increased over the past 30 years at an average rate of 0.34° C per decade (O’Reilly et al., 2015). This overall warming trend can result in extreme changes in both physical and biological properties of whole-lake ecosystems, affecting for example the duration of seasonal stratification or thermocline depth (Adrian et al., 2009) and resulting primary productivity and phytoplankton blooms. In less resilient systems, warming may shut down vertical mixing, causing dramatic changes in primary productivity patterns, deep water hypoxia and, eventually, fish kills (Odermatt et al., 2018). Likewise, in case of changing precipitation regimes, lake turbidity changes can impair vertical lake mixing behaviour by reducing mixed layer thickness through attenuation of sunlight penetration (Kirillin and Shatwell, 2016).

The C-GLOPS data allows for the first time the possibility to assess the extent to which anthropogenic warming and eutrophication conspire to alter the mixing behaviour of lakes at a global scale. Since mixing behaviour is a fundamental property determining lake ecology, a shift from well-mixed to more strongly stratified lakes may drive important changes in lake ecological function and the availability of ecosystem services such as water quality and fisheries. Against the background of such potentially irreversible dynamics, we investigate indicative spatio-temporal patterns accessible by C-GLOPS data, comparable datasets and ancillary data, with the aim of characterizing recent and future shifts in lake biophysical properties, and identifying whether such shifts are continuous, gradual and reversible in nature, or not.


Adrian, R., O’Reilly, C.M., Zagarese, H., Baines, S.B., Hessen, D.O., Keller, W., Livingstone, D.M., Sommaruga, R., Straile, D., Van Donk, E., et al. (2009). Lakes as sentinels of climate change. Limnol. Oceanogr. 54, 2283–2297.

Kirillin, G., and Shatwell, T. (2016). Generalized scaling of seasonal thermal stratification in lakes. Earth-Sci. Rev. 161, 179–190.

Odermatt, D., Danne, O., Philipson, P., and Brockmann, C. (2018). Diversity II water quality parameters from ENVISAT (2002–2012): a new global information source for lakes. Earth Syst. Sci. Data 10, 1527–1549.

O’Reilly, C.M., Sharma, S., Gray, D.K., Hampton, S.E., Read, J.S., Rowley, R.J., Schneider, P., Lenters, J.D., McIntyre, P.B., Kraemer, B.M., et al. (2015). Rapid and highly variable warming of lake surface waters around the globe. Geophys. Res. Lett. 42, 10773–10781.

Scheffer, M., Bascompte, J., Brock, W.A., Brovkin, V., Carpenter, S.R., Dakos, V., Held, H., van Nes, E.H., Rietkerk, M., and Sugihara, G. (2009). Early-warning signals for critical transitions. Nature 461, 53.

Updating of surface subsidence using SAR interferometry after counter measures by activating an old reservoir for water consuming control.
Issaak Parcharidis1 & Asimakis Fylaktos1
Harokopio University, Athens, Greece
Land subsidence caused by compaction of overdrafted aquifer systems is a worldwide problem in agricultural heavily dependent on ground water supplies. The overdraft of aquifer systems containing fine-grained silt and clay layers (aquitards) results in a vast, one-time release of water of compaction from the aquitards.During this typically slow drainage process, permanent land subsidence occurs primarily due to the irreversible (inelastic) compaction of aquitards.
Eastern Thessaly plain (Central Greece) represents a tectonic depression of Quaternary age. The plain corresponds to a gently SE dipping, nearly planar surface covered by a thick (up to 50 m deep) alluvium layer, relict of a Quaternary Lake, which was gradually restricted to the Karla Lake, at its lowest, SE part. This lake was artificially drained in the 1960s to provide cultivated land. The SE part of the plain (former Karla lake), lower energy deposits, mostly clay and silt predominate are identified, deriving from erosion of Neogene sediments at the SW margins of the plain.A consequence of drying and decline of rainfall was the rapid fall of groundwater which provoked high rates of subsidence as previous research studies show.
As a result of all the above, and following strong protests by the local populations, it was the decision of construction of a 42,000-acre reservoir in the lower part of the former Karla Lake near the village of Kanalia. On 2010 started the refilling and the generation of the new Karla lake aiming the rise of the underground aquifers and the restoration of the water potential.
This study aiming to update the previous investigations (Parcharidis et al. 2011, Benekos et al. 2014, Foumelis et al. 2016) about subsidence, due to overpumping and drought, occurred in the area after the recharge of the lake and verifying or not the phenomenon of deceleration probability. For this purpose Sentinel 1 A & B SLC IW scenes Dual Polarization (vertical Transmit and Vertical Receive) mode, in ascending orbit, covering the period 2014-2018, In total 89 SAR scenes were used to create deformation maps following the Persistent Scattrers Interferometry technique. The process was conducted in SARPROZ software (developed by Dr. Perissin, Purdue University, WestLafayette, IN, USA written in Matlab, Perissin et al. 2011).The final outcome was geocoded to and displayed in Google Earth.Additionally, optical data from Landsat program and Copernicus Sentinel 2 will be used to monitor the evolution of water recharge of the new lake as well as seasonal changes in the level for one year and compare with the corresponding annual interferometric results.
References
Benekos G., Derdelakos K. , Bountzouklis Ch. , Parcharidis I. 2014. Monitoring the subsidence in the plain of south Thessaly with SAR interferometry. Proceedings of 10th International Geographical Congress, i-xvi, 1-1866, p. 1313-1321.
Foumelis, M., Papageorgiou, E. & Stamatopoulos C., 2016. Episodic ground deformation signals in Thessaly Plain (Greece) revealed by data mining of SAR interferometry time series. International Journal of Remote Sensing, 37 (16), 3696-3711, doi: 10.1080/01431161.2016.1201233
Parcharidis, I., Foumelis, M. & Katsafados, P., 2011. Seasonal ground deformation monitoring over Southern Larissa Plain (Central Greece) by SAR interferometry. 9th International Hydrogeological Congress, In: Advances in the Research of Aquatic Environment, N. Lambrakis, G. Stournaras & K. Katsanou (eds), Environmental Earth Sciences, Springer, vol. 2, 497-504.
Perissin D., Z. Wang, and T. Wang, “SARPROZ InSAR Tool for Urban Subsidence/manmade Structure Stability Monitoring in China, The,” in Proc. of ISRSE 2011, Sidney (Australia), 2011

Cerema (centre d'études et d'expertise sur les risques, l'environnement, la mobilité et l'aménagement) is a French public entity in charge of supporting national and local authorities in terms of sustainable development, environment, transports and urbanism. The organization is a center of technical and scientific resources involved in the design, implementation and assessment of public policies.
Since 2013, Cerema has been working, in support of the French Embassy in Indonesia, on the problematic of the city of Semarang. Semarang, which is a coastal city, is the capital and largest city of Central Java province in Indonesia. It faces significant marine flooding due to the combination of two phenomena: sea level rise and subsidence, which reaches 14 cm/year in some areas of the city.
The subsidence is related to the fact that the city of Semarang was developed on sediments which are recent and therefore affected by compaction. This natural phenomenon is worsened by human activities. Subsidence rates can reach 10 to 14 cm/year in some areas, in particular along the coastal strip. At the same time, sea level rises by an average of 1 cm per year. The coastal strip is then subject to frequent marine flooding, impacting 200,000 to 600,000 people, especially in periods of heavy rainfall combined with tidal.

The Cerema project aims at developing a local dynamic of resilience to natural risks associated with subsidence. Cerema is participating in setting up relations between Dipanegoro University (UNDIP) and local decision-makers in order to help them move from scientific knowledge to effective risk mitigation.
It’s in this framework that TRE ALTAMIRA, world leader in SAR Interferometry, has carried out, in partnership with Cerema, an historical study of ground motion over Semarang. Sentinel-1 data acquired from October 2014 to July 2018 have been processed with the SqueeSARTM chain to retrieve ground motion over the city of Semarang. The results show a large subsidence pattern with motion reaching 12.5 cm/year along the satellite line of sight. InSAR data, integrated with Cerema knowledge about the site and other in situ measurements, will be presented and discussed, highlighting the importance of regular satellite observations over coastal areas severely affected by climate changes and the complementarity of InSAR with conventional geodetic data.

The Copernicus Imaging Microwave Radiometer (CIMR) is a High Priority Candidate Mission for the Copernicus Space Component Expansion programme, which would fly on a Sentinel satellite at the horizon of 2025. It is planned that CIMR will provide observations in the microwave spectrum from L- to Ka-band (1.4 to 37 GHz), at much higher spatial resolution and accuracy than past or future missions. CIMR’s focus is on retrieval of sea ice parameters and sea surface temperature (SST) in polar regions. As a Sentinel mission with a long-term operation period CIMR will provide observations of the predicted “New Arctic” by the mid-century and beyond.
The Arctic experienced an unpreceded warming and decrease of sea ice in recent decades. Climate models predict a continuation of the current retreat of sea ice cover and lengthening of the melting season for the next decades and beyond (Collins et al., 2013). This will make Arctic waters more attractive and accessible for shipping and off-shore activities (e.g., Melia et al., 2016). Predictions suggest that shipping from Europe to Asia via the Arctic becomes 10 days faster by mid-century, i.e., during the CIMR operational period. By late century, moderately ice-strengthened vessels likely can travel through the Arctic almost year-round (10–12 months). The retreating sea ice will allow the shipping routes to extend further north and further away from coastlines, which will increase the need in spatial coverage of satellite observation systems. The extended open ocean areas will also allow increased fishing activities in the Arctic Ocean and marginal seas. Larger all-year around open water areas might become attractive for offshore industries like oil industry.
For these activities timely information about the ice coverage and short-term forecast of ice situation for the complete Arctic will be needed. The demands for marine safety will increase to provide timely response to accidents like oil spills in ice covered waters.
With its relatively high spatial resolution of <4 km, sub-daily coverage of all polar regions without any unobserved areas around the pole (no pole hole), CIMR is ideally suited to address these needs in operational applications. CIMRS capabilities are especially applicable for model initialization for short to medium-range sea ice forecasts.
Here we will show how the shipping and off-shore industries will benefit from CIMR observations in a predicted future Arctic with reduced sea ice cover. Exemplary future sea ice scenarios from CMIP5 model simulations are analysed in combination with current AMSR2 sea ice concentration on a 3 km grid as a substitute for CIMR to demonstrate what benefit such an observing system would bring for Copernicus and the EU. The following questions are addressed:
• What benefits will the higher resolution of CIMR bring in comparison to the 25 km sea ice concentrations expected from the MWI instrument on the MetOp-SG satellites?
• What future shipping routes and potential fishing grounds are predicted to open up and what will be the CIMR contribution to monitor these, especially close to the pole and within archipelagos?
• How will the CIMR high temporal resolution of sub-daily coverage help to better monitor the polar regions?
• How will CIMR help to address the EU Arctic Policy, CMEMS, Polar Code, and MSAR?

References:
Melia, N., K. Haines, & E. Hawkins (2016). Sea ice decline and 21st century trans-Arctic shipping routes. Geophys. Res. Lett., 43, 9720-9728. doi:10.1002/2016gl069315

Collins, M., R. Knutti, J. Arblaster, J.-L. Dufresne, T. Fichefet, P. Friedlingstein, X. Gao, W.J. Gutowski, T. Johns, G. Krinner, M. Shongwe, C. Tebaldi, A.J. Weaver and M. Wehner, 2013: Long-term Climate Change: Projections, Com- mitments and Irreversibility. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA

Services supporting risk management are commonly divided according to the different step of the disaster management cycle. These include: (1) prevention, to minimize future losses; (2) preparedness and crisis management, often focused on saving lives, and (3) recovery and post-crisis management aiming at reestablishing services supporting human activities. As boundary conditions are changing with climate change (e.g., sea level rise, mean and extreme temperatures and precipitations), hazards are evolving in turn and new needs for information are emerging. These needs include: (1) detection and attribution to climate change; (2) understanding and quantifying future impacts of climate change; (3) supporting adaptation to climate change.

Space-based Earth Observations have long provided essential information in support to risk management and climate impacts in the areas of soil and coastal erosion, coastal and inland flooding, as well as geohazards such as ground motions, landslides, earthquakes and volcanic eruptions. Earth Observation is also an obvious resource in the area of detection and attribution of impacts of climate change. However, less attention has been given so far regarding how Earth Observation can support impact assessments and adaptation.

Based on a literature review and examples of studies in the area of coastal, hydro-meteorological and geo-hazards, this presentation examines how space-based Earth Observations:
- have addressed the needs for information in the area of risk management so far: we show that efforts have essentially focused on hazard assessments or supporting crisis management, whereas a number of needs still remain partly fulfilled in the area of vulnerability and exposure mapping.
- support detection and attribution of climate change: as already highlighted in the 5th assessment report of the IPCC (WG2, Ch18), we show that the lack of data often prevents from being conclusive in this area.
- support future impact assessments: while it is counter-intuitive, observations are in fact embedded in any future impact assessment studies, and lack of observations may in fact hamper the possibility to identify when impacts of climate change have or will emerge from the current variability of events.
- help understanding and evaluating adaptation options and needs, which is an area where research is needed at the interface between social and economic sciences and Earth Observations.

Overall, our review demonstrates that the full potential of space-based Earth Observations has not been fully used so far: some phenomena with important impacts for the society remain incompletely observed (e.g., shrinking and swelling of clays), and many needs of adaptation practitioners still need to be addressed. For programmes such as Copernicus and the Sentinel constellation of satellites, this offers research opportunities and raises challenges in the areas of sensor development and algorithm developments.