A recipe for desert : analysis of an extended Klausmeier model

In drylands, water is a crucial ingredient for the sustenance of vegetation. Due to climate change, dry areas are projected to become dryer, which puts the vegetation under increasing environmental pressure. If environmental conditions deteriorate, the amount of vegetation may become critical, beyond which the vegetation suddenly disappears. We study a phenomenological model - the extended Klausmeier model - which models the interaction between water and vegetation in drylands. In this spatially explicit model, due to drought, homogeneous vegetation transforms into a spatial pattern. We study different scenarios under which subsequent patterns form under decreasing rainfall conditions, eventually leading to a bare desert state.NWO ComplexityUBL - phd migration 201

Chapter 1.2: Tipping points in the cryosphere

Drastic changes in our planet’s frozen landscapes have occurred over recent decades, from Arctic sea ice decline and thawing of permafrost soils to polar amplification, the retreat of glaciers and ice loss from the ice sheets. In this chapter, we assess multiple lines of evidence for tipping points in the cryosphere – encompassing the ice sheets on Greenland and Antarctica, sea ice, mountain glaciers and permafrost – based on recent observations, palaeorecords, numerical modelling and theoretical understanding. With about 1.2°C of global warming compared to pre-industrial levels, we are getting dangerously close to the temperature thresholds of some major tipping points for the ice sheets of Greenland and West Antarctica. Crossing these would lock in unavoidable long-term global sea level rise of up to 10 metres. There is evidence for localised and regional tipping points for glaciers and permafrost and, while evidence for global-scale tipping dynamics in sea ice, glaciers and permafrost is limited, their decline will continue with unabated global warming. Because of the long response times of these systems, some impacts of crossing potential tipping points will unfold over centuries to millennia. However, with the current trajectory of greenhouse gas (GHG) emissions and subsequent anthropogenic climate change, such largely irreversible changes might already have been triggered. These will cause far-reaching impacts for ecosystems and humans alike, threatening the livelihoods of millions of people, and will become more severe the further global warming progresses. The scientific content of this chapter is based on the following manuscript in preparation: Winkelmann et al., (in prep