Academic journal article Science Scope

Flooded! an Investigation of Sea-Level Rise in a Changing Climate

Academic journal article Science Scope

Flooded! an Investigation of Sea-Level Rise in a Changing Climate

Article excerpt

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Increasing atmospheric greenhouse gas concentrations and the effects on Earth systems are better understood due to the attention being given by the world community to their regional impacts. Of particular concern are the implications of melting ice for sea-level rise, the significance of ocean acidification for marine ecosystems, and the risks to global agriculture and water supply posed by the expanding tropical belt.

Simply stated, sea-level rise (SLR) is a rise in the water level of the Earth's oceans. Most people would agree that melting ice would generate more water; however, not all ice melt affects SLR. There are two major kinds of ice in the polar regions: sea ice and land ice. Land ice contributes to SLR and sea ice does not. In this article, we -will explore the characteristics of sea ice and land ice and provide some hands-on activities to help clear up any misconceptions about melting ice.

Sea-level rise and its consequences

For the last 3,000 years, sea level has remained nearly stable (Rignot and Cazenave 2009). As available measurements and accuracy have increased in recent decades, significant SLR has been observed during the late 1800s and into the 1900s. Since the early 1990s, sea-level variations have also been accurately measured by satellite altimetry. According to the Global Outlook for Ice and Snow published by the United Nations Environment Programme (UNEP), sea level is rising at an increasing rate (2007). The average rate of SLR for the 20th century was 1.7 mm per year. That rate is currently up to 3.1 mm per year and is expected to continue increasing. From the mid1990s to 2008, melting glaciers constituted about 28% of the observed SLR, with melting glaciers in Alaska alone accounting for about one-third of this percentage (Rignot and Cazenave 2009). The Greenland and Antarctic ice sheets contributed roughly 17%, and the remaining 50% of the rise in sea level during this same time period can be explained by ocean warming and thermal expansion (water expands when it heats up).

Consequences of climate changes can include, but are not limited to, increased drought, increased flooding, extreme temperatures (hot and cold), and SLR. When a portion of landscape becomes inhospitable for any number of reasons, people must move to different locations. These environmental refugees are being displaced by climate change. This impacts the economies of the current and future homes of a population in a variety of ways. SLR caused by climate change is already causing changes in physical processes, economic activity, and social systems in coastal regions (Li et al. 2009). SLR is a major concern for populations living in low-lying coastal regions (about 25% of humans), because it "will give rise to inundation (both temporary and permanent flooding), wetland loss, shoreline erosion, and saltwater intrusion into surface freshwater bodies and aquifers, and it will raise water tables. Figure 1 shows the estimated population impacted by a uniform one-meter rise in sea level.

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C[O.sub2] remains in the atmosphere for more than 400 years (Solomon et al. 2007), a process referred to as residence time. Greenhouse gas emissions are thus still in the atmosphere, meaning there is already a certain amount of SLR locked in for the next several decades. These rising sea levels have already affected millions of people and will potentially affect millions more, especially those on small islands and coastlines worldwide.

Sea ice vs. land ice

At first glance, the formation or type of ice does not appear to be a complicated concept. However, upon further investigation, the formation of ice and its physical properties can vary quite a lot. As water cools, it contracts until the temperature of maximum density is reached. Further cooling actually results in expansion. Sea ice forms when the surface cools such that water begins to freeze. …

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