Rising Seas

by Owen Dubeck

Coral Davenport summarizes the effects of rising sea levels across Kiribati, Greenland, Panama, Fiji and the United States. Kiribati, a chain of islands northwest of Australia, will see some of the worst consequences. Given the island’s low elevation, it could be completely underwater by 2100. Fortunately, the government has urgently responded, buying over 6,000 acres of land in Fiji. This land can function both as a source of crops and possibly a new home. Continue reading

Multi-millennial climate change projection

by Simon Bjerkholt

What will the world look like due to humankind’s mistreatment of the environment in 100 years? 1000? 10000? Peter U. Clark et al. (2016) attempt to answer these questions in their article “consequences of twenty-first-century policy for multi-millennial climate and sea-level change” in the journal Nature Climate Change. According to their research and projections, the long term future of our climate looks very dreary. Continue reading

Climate Change Threatens the Javanese Way of Life

 

by Blaine Williams

In the face of climate change and rising sea levels, atolls––rings of islands formed by coral reefs––are some of the most vulnerable human-inhabited regions. In the atoll of Ontong Java, the world’s largest atoll, climate change has begun to affect the quality of life for the locals, and will create more hardship in the years to come. The highest point of the Ontong Java atoll is 10 feet above sea level, and with sea levels rising at a rate of a few millimeters a year, the islands are losing more and more land to the ocean. Faced with issues such as irregular weather patterns and imminent land loss, a key struggle for the inhabitants of Ontong Java is adapting to these changes and attempting to take them in stride. Continue reading

Sea-Level Rise Puts Indo-Pacific Mangrove Forests at Risk

by Grace Stewart

Mangroves provide an array of ecosystem services, from coastal protection to fishery support to carbon sequestration, all of which are at risk in the Indo-Pacific region due to sea-level rise (SLR). SLR can lead to inundation of these habitats and shoreline retreat. Lovelock et al. (2015) analyzed recent trends in mangrove surface elevation, finding that SLR could be combated when sediment availability allowed for soil-surface elevation gain at a rate that exceeded SLR. However, in 69% of the sites studied, SLR rate was exceeding the rate of soil-surface elevation gain. Lovelock et al. also presented a model based on field data that suggests submergence of forests with low tidal range and low sediment supply as early as 2070. Continue reading

Are Major U.S. Cities Doomed by Rising Sea Levels?

by Pushan Hinduja

As climate change becomes more and more of a threat, people around the world worry about the fate of US coastal cities that might one day be entirely submerged. Matthew E. Kahn, a visiting professor of economics and spatial science at the University of Southern California argues that these cities shouldn’t worry, as they will adapt and rise above the effects of climate change. Khan begins by citing a Rolling Stone article published in 2013 that predicted Miami, “the nation’s urban fantasy land” turning into an “American Atlantis.” Interestingly enough, this threat is not unique to Miami: the majority of Americans live within 50 miles of an ocean, whether that be in New York, Seattle, San Francisco, or Los Angeles, among many more. An economist by training, Khan argues that based on his understanding of how people invest their money during times of crisis and uncertainty, US coastal cities will successfully adapt to climate change and thus be “just fine.”

To be more specific, coastal city residents and firms are currently all aware that the dangers of rising sea levels are imminent. As a result, there is a huge market incentive for adaptation and the development of innovative solutions to these problems. Additionally, thanks to the “invisible hand,” homeowners will feel the pressure to take self-interest and protect their properties as best as they can to try to maintain value. Khan compares this to the increase in research in the pharmaceutical industry when there is expected demand for a certain drug.

In terms of actual adaptation to the rising sea levels, cities around the US will employ a variety of different tactics, ranging from the upgrading of existing structures to construction of new climate change-resilient structures using modular materials. Khan argues that the rising demand for these new developments will recruit young and new talent into the field, which will lower overhead costs for adaptation, ultimately making the whole system even more sustainable. Another key component of adaptation to climate change is the ability to move to “higher ground.” Khan argues that loss of land due to rising sea levels will not reduce the population in an urban area, because of the ability to retreat and develop on lower risk high ground.

Coastal cities as America’s economic hubs won’t be affected either, as the “physical place” is not what defines an economic hub; instead it is the human capital that clusters in any specific location that makes that place an economic hub. Thus rising sea levels may cause the economic hubs to change locations, perhaps only slightly, but will not negatively harm the U.S. economy.

Ultimately, Khan argues that although rising sea levels due to climate change will play an important role in defining coastal cities in the future, it will not render them underwater wastelands. In fact, US coastal cities will undergo a renaissance of “market-driven adaptation” that will cause both the economy and the population that currently resides in these ‘high threat’ areas to thrive.

Kahn, Matthew E., 2016. Rising Sea Levels Won’t Doom U.S. Coastal Cities. Harvard Business Review.

https://hbr.org/2016/01/rising-sea-levels-wont-doom-u-s-coastal-cities

 

China’s Sea Level Change

by Xiaoshi Zhu

As climate change becomes more dramatic in recent years, the rising sea level has begun to threaten more countries in the world. Among these regions, China has the largest population that will be affected by the likely inundation—a staggering 85 million people. In his article China’s Sea Change published in December 2015 on The Globe and Mail, Nathan VanderKlippe talks about how serious the problem has become and the actions that the Chinese government has taken to improve the bad situation. Continue reading

Interdisciplinary Asessment of Sea-Level Rise and Climate Change Impacts on the lower Nile Delta, Egypt

by Rebecca Herrera

The Mediterranean region will continue to experience climate change in much of the same way as other arid regions around the world. Susnik et al. (2014) set our to find our how the Nile River delta in Egypt experiences more intense droughts and water shortages, rising regional temperatures, an increased frequency of flash flood events, and sea level rise. It is critical to understand of how these climactic changes will impact the people residing in the delta. Susnik et al. take an integrated and interdisciplinary approach to studying the effects of sea level rise (SLR) on the lower Nile delta and the greater Alexandria areas by analyzing the results of three complementary projects; which reveal that water overexploitation exacerbates land subsidence and accelerates saline intrusion of soils and groundwater which has radiating effects on employment as well as placing additional pressure on agricultural lands and regional development. Continue reading

A Public Health Policy Approach To Rising Sea Levels

by Sarah Whitney

Robin Kundis Craig (2010) concludes that it is absurd to expect governments to put policies in place now that predict and manage the long-term effects of rising sea levels. Craig argues that governments can prevent the extent of damages caused by rising sea levels by implementing a policy focusing directly on public health. She notes that scientists are still unsure exactly how high the seas will rise. Their predictions, she states, are uncertain as they are based upon scientific assumptions and factors like the effect of current and future mitigation methods, (the methods combating greenhouse gas emission). Craig also states that it is unreasonable to define adaptive measures to govern climate change almost three centuries from now as new information will inevitably arise. One can reasonably assume however, that humans will still retain the same basic desires such as health and comfortable living conditions in the distant future. This assumption can be used to form a preventative policy that benefits society without the need to fully comprehend all the uncertainties of rising sea levels. A public health approach aimed at the needs and concerns of humans is an adaptable policy that can remain stable as the discoveries and effects of climate change arise. Continue reading

Sea Level Rise and the Uncertainty of Future Climate Conditions

Sea level rise (SLR) is one major consequence of global warming and the resulting climate change. Sea levels have already risen 1.8 cm/decade during the 20thcentury and this trend is expected to increase rapidly in the coming years. Sea level rise is mostly controlled by temperature and salinity changes in the oceans and continental ice sheet buildup and melting. As such, a rise in sea level is seen when there is warmer and less saline water as well as when continental ice melts.  Hu and Deser (2013) were able to analyze SLR rates for the future by using the Community Climate System Model Version 3 (CCSM3). This system was able to present 40 different climate change projections in order to understand the uncertainty that is related to the future climate variability.  The results of this experiment show the extreme uncertainty of the climate moving forward and that the SLR varies by a factor of 2 depending on global location with large increases in sea level in some areas and decreases in others. —Chloe Mayne

Hu, A. and Deser, C., 2013. Uncertainty in future regional sea level rise due to internal climate variability. Geophysical Research Letters 40, 2768—2772

Hu and Deser used the Community Climate System Version 3 (CCSM3) in order to model the rates of future sea level rise.  This system used 40 projections, called ensemble members, and began at the end of the 20th century. Each projection included similar levels of greenhouse gases, ozone, solar and aerosol over a period of 60 years from 2000—2006. In addition, the states of the ocean, sea ice, and land were also static. The differences in projections came from using atmospheric conditions found on days between December 1999 and February 2000. to encompass the variety of atmospheric conditions that are plausible over the next 60 years. It is, of course, impossible to predict future precisely, but this model is able to represent an array of future possibilities for sea level rise as greenhouse gas concentrations continue to rise and add to global warming.
The result of Hu and Deser’s study looked at the mean SLR over the last 20 years of the 60-year period. The global mean SLR was very similar for most cities at around 11+/- 0.2cm for the 20 year period.  On a more local scale, the regional SLR varied by a factor of 2. An example of the local scale SLR can be seen when looking at the large range for San Francisco, which was 4.3-9.6 cm.  Some of the ranges seen showed a peak in the distribution frequency (a large range for the SLR) while other cities showed no peak at all, with a constant rate of SLR.
The geographic distribution of the sea level projections was found to be positive across the globe, except for in the Southern Ocean. In the North Atlantic and Arctic the rate of SLR was projected to be around 5 cm/decade while only about 1-2 cm in the Pacific and 2-3 cm in the Atlantic. These numbers are due to the increase in the amount of heat that the ocean can store as less heat is being lost to the atmosphere. Most uncertainty is found in the high and middle latitudes around the Arctic Ocean, Southern Ocean, North Atlantic and North Pacific. Less uncertainty is found in areas that are tropical as well as in the North Indian Ocean.
Sea level rise is also associated with changes in ocean circulation, which are considered a dynamical component. These changes occur as a result of wind and buoyancy forcing.  Looking at two specific projections for SLR, it is possible to see the trends of sea level pressure, SLP, which is a measure of wind forcing. The results showed that SLP was weaker or stronger depending on which ocean basins were considered, probably resulting in different ocean circulation patterns and differences in sea level rise.  In addition to wind, buoyancy forcing, as a result of the Atlantic Meridional Overturning Circulation (AMOC), plays a large factor in ocean circulation. The AMOC moves warm waters north where they become cold and dense and sink deep down into the ocean. These waters then eventually move south and are cycled through the ocean conveyor belt. As GHG emissions continue to grow, it is expected that the AMOC will slow down and sea levels will increase in the Atlantic without the cold water in the north being forced deep into the ocean.

Disregarding ice melt, the primary increase in sea level rise was found to be expansion of seawater as the temperatures rise but it is clear from their study that there is a great amount of uncertainty as to future SLR. 

Sea Levels and Ocean Thermal Expansion

Data show that sea levels have been rising significantly over the past half century. The contributions from thermal expansion of the oceans, the melting of glaciers, and loss of ice masses in Greenland and Antarctica are commonly studied, but together they do not account for the total sea level rise (SLR). The rate of SLR is ~1.8 mm yr–1, but the total contributions from these sources is estimated to be about ~1.1 mm yr–1, which leaves ~0.7 mm yr–1 unaccounted for. Pokhrel et al. (2012) examined terrestrial water storage, namely reservoir water impoundment and unsustainable groundwater irrigation, and found that these types of sources likely contribute about 0.77 mm yr–1 to SLR. Thus, anthropogenic water uses contribute greatly to changing sea levels, and can help close the gap in the global sea level rise.¾Olivia Jacobs
Pokhrel, Y.N., Hanasaki N., Yeh, P.J., Yamada, T.J., Kanae, S., Oki, T. Model estimates of sea-
level change due to anthropogenic impacts on terrestrial water storage. Nature
Geoscience 5, 389392.

Pokhrel et al. (2012) used an integrated water resource assessment modeling framework to analyze the potential contributions of anthropogenic sources to global sea level change (SLC). They estimated many values such as the amount of water lost to seepage in reservoirs, the number of years to fill a reservoir, and the rate of change in loss over time, because no real values are currently available. Using these estimates and data from numerous supplementary sources, they concluded that the global reservoir capacity is about 8,000 km3. They also estimated unsustainable groundwater use based on total water demand and the availability of water from near-surface sources, which they concluded gave them an accurate estimate of groundwater contributions to SLR.
                  By comparing their estimated values with other model simulations, Pokhrel et al.were able to estimate the relative contributions from different types of terrestrial water storage (TWS) to SLC. They focused on artificial reservoir impoundment and unsustainable groundwater use and found that these two variables can close the gap in SLC quite successfully. Artificial reservoirs generally cause a drop in the sea level by holding water over land, and this study estimated that the cumulative contributions of reservoir capacity and storage to SLC was ~22 and ~15 mm, respectively. Further, when seepage from reservoirs was accounted for, the estimates of artificial reservoir capacity was ~31 mm, and the actual estimated contribution was ~21 mm. In both of these scenarios, the scientists noted a large discrepancy between reservoir capacity and reservoir storage.
Unsustainable groundwater use contributes to SLR because water is removed from the ground and eventually ends up in the oceans. Here, the scientists estimated groundwater depletion (GWD) has contributed ~48 mm to cumulative SLR. Also, climate-driven terrestrial water storage (TWS), including soil moisture and snow and river storage exclusive from Greenland and Antarctica, has a net contribution of ~8 mm to global SLR. Thus, while climate-driven TWS has significant decadal and annual variation, the long-term contributions to global SLR are relatively small and anthropogenic redirecting of water contributes to SLR much more significantly. Pokhrel et al. also considered the uncertainty in their estimates, and found that the uncertainty of net TWS, including groundwater depletion, climate-driven TWS, and reservoir storage, could be as high as 30%.
Overall, the annual estimated contribution of these TWS sources to SLC was +0.77 mm yr–1, which is close to the previously unexplained gap in SLR of 0.70 mm yr–1. Individually, the estimates were +1.05 mm yr–1 from groundwater, +0.08 mm yr–1 from climate-driven TWS,       –0.39 mm yr–1 from reservoir storage, and +0.03 mm yr–1 from the Aral Sea, which was a main source of water diversion for irrigation. Comparatively, the contribution from thermal expansions of the oceans was ~0.42 mm yr–1, ~0.5 mm yr–1came from glaciers and ice caps melting, and ~0.19 mm yr–1 from ice-mass loss in Greenland and Antarctica.
The trends in TWS over the past 50 years indicate that groundwater depletion has been increasing significantly over time and may increase more in the future, and the climate-driven TWS has also been increasing in recent years. Reservoir impoundment has also recently leveled off, so there may be an even greater contribution to SLR from TWS sources in the future, and while there is obvious uncertainty in estimations used in this study, they are all within the plausible limits for many countries. The scientists note that some sources, such as the effects of deforestation and wetland drainage, were not considered, but these sources have previously been shown to contribute very little to global SLR. Thus, these TWS sources can help close the gap in estimations of global sea-level change, and can help shed light on the future forecasts for global SLR.