Sea‐Level Rise and Variability: Synthesis and Outlook for the Future

Abstract

Coastal zones have changed profoundly during the 20th century with growing populations and economies (Figure 1.2 ). Increasing urbanization was a major driver of this change. Today, many of the world ' s megacities are situated at the coast. At the same time, sea level has been rising and is projected to continue to rise further. However, coastal developments have generally occurred with little regard to the consequences of rising sea levels, even in developed regions such as Europe (Tol et al. 2008 ). An improved understanding of sea -level rise and variability is required to reduce the uncertainties associated with projections for sea -level rise, and hence contribute to more effective coastal planning and management.The preceding chapters have provided an overview of our understanding of sea -level change. These chapters benefi tted from the discussion of position papers at a workshop on sea -level rise and variability held under the auspices of the World Climate Research Programme (WCRP) at the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientifi c and Cultural Organization (UNESCO) in Paris in 2006. The workshop was attended by 163 scientists from 29 countries representing a wide range of expertise and supported by 34 organizations. The workshop prompted and underpinned new research initiatives. This chapter provides a synthesis of the fi ndings and recommendations from this community discussion, including a summary

Sea level trends, interannual and decadal variability in the Pacific Ocean

“…That is, the spatial pattern in Figure 1a can be approximated to the first order by a sea level trend as a result of aliasing of the decadal variability (Figure 4e) plus the global mean sea level rise rate of about 3.3 mmyr −1 over the current study period [ Zhang and Church , 2011]. Note the sea level rise rates associated with anthropogenic climate change are generally not expected to be geographically uniform [e.g., Church et al , 2010].…”

“…Many regions experience a higher or lower rate of sea level change than the global average. In some locations, the linear trend over 1993–2009 based on altimeter measurement can be five times the global average value [ Church et al , 2010]. Large‐scale climate phenomena induce regional climate variability on interannual, decadal and inter‐decadal time scales.…”

“…[2] Sea level changes occur over a wide range of temporal and spatial scales. High-quality long-term tide gauge data indicate the global mean sea level (GMSL) has been rising for the past 100+ years [e.g., Douglas, 2001;Church andWhite, 2006, 2011]. Since the launch of the Topex/ Poseidon altimeter, near-global altimeter measurements have been used to infer rising GMSL [e.g., Mitchum et al, 2010;Cazenave and Llovel, 2010].…”

“…Since the launch of the Topex/ Poseidon altimeter, near-global altimeter measurements have been used to infer rising GMSL [e.g., Mitchum et al, 2010;Cazenave and Llovel, 2010]. The temporal Linear Trend (LT) is a popular metric often used to quantify sea level change at both global and regional scales, despite the possible presence of nonlinear trends [e.g., Church andWhite, 2006, 2011;Jevrejeva et al, 2006;Woodworth, 2006;Merrifield et al, 2009;Woodworth et al, 2009;Merrifield, 2011]. There are many studies examining the regional sea level LT from the available altimeter data over time spans ranging from 3 to 18 years [e.g., Nerem, 1995;Cabanes et al, 2001;Wunsch et al, 2007;Cheng et al, 2008;Cazenave and Llovel, 2010;Bromirski et al, 2011].…”

The Lefkada barrier and beachrock system (NW Greece) — Controls on coastal evolution and the significance of extreme wave events

“…Since the deceleration of the eustatic sea-level rise in the midHolocene, coastal geomorphological processes along sedimentary coasts have been increasingly influenced by the interaction of erosion, supply and compaction of sediments as well as local tectonics (Stanley and Warne, 1994;Woodroffe and Nash, 1995;Morton, 2009;Church et al, 2010;Lambeck et al, 2010). As with landscapes in general, coastal systems tend to adjust towards or oscillate around equilibrium conditions (Scheidegger, 1994), involving an equilibrium geomorphology that changes over time.…”