Global Climate Change Impact on the Upper Texas Coast

April 7, 2014 3:50 pm6 comments

Very few scientists still question global warming and the role humans have had in the process, while outside the science community it is largely viewed as a prediction. The reality is that climate change and associated accelerated sea-level rise are not predictions. Tide gauge records are supported by satellite data telling us that the rate of rise has significantly increased within the past two centuries.

Great_Egret_by_Sarowen_Flickr

Sarowen via Flickr

These combined results indicate that the rate of global sea-level rise averages ~3.0 mm/yr, although the actual rate varies regionally (Rahmstorf et al., 2007; Church et al., 2011; Carlson, 2011). However, within the northwestern Gulf of Mexico, subsidence contributes to relative sea-level rise with rates in east Texas as high as 6.0 mm/yr (Paine, 1993). Regardless of the actual value, this is a multifold increase over the long-term rate of the past few thousand years of ~0.40 to 0.60 mm/yr (Milliken et al., 2008).

Pine Island Glacier rift and break off series.

A massive rift and break off of Pine Island Glacier in Western Antartica, beginning in 2011.  Credit: USGS LandSat (top), NASA ICE via Flickr (middle), USGS (bottom).

The only mechanisms that can cause such a rapid increase in the rate of sea-level rise are heating and expansion of the oceans and melting of glaciers and ice sheets; both are known to be occurring at unprecedented rates. The main uncertainty in predicting the actual magnitude of sea-level rise is the contribution from the Greenland and Antarctic ice sheets, but both ice sheets are exhibiting signs of instability.

It is generally accepted that the rate of sea-level rise will continue to increase during the 21st century given rates of heat uptake by the oceans, the fact that the vast majority of glaciers have shifted to a negative mass balance and recent observations indicating a negative mass balance for large portions of the Greenland and West Antarctic ice sheets (Rignot et al., 2011).

While an increase of only a few millimeters per year may seem insignificant, numerical models indicate that an increase of just 1 mm/yr in the rate of rise can result in an increase in the rate of shoreline retreat of several meters per year. It has been more than 7,000 years since sea level was rising as fast as the current rate. At that time the upper Texas coast experienced episodes of retreat as high as 60 m/yr (Figure 1, Rodriguez et al., 2004 ). Indeed, most modern barrier islands and modern bays did not form until after the rate of sea-level rise had slowed to less than 1 mm/yr (Anderson, 2007). Add to the equation the impacts of human alteration to sediment delivery to the coast, such as construction of dams that prevent sediment being carried to our bays and coastal lands, and it is easy to understand why our coast is experiencing such dramatic change.

Anderson Figure 1Anderson Figure 2Current rates of shoreline erosion along the upper Texas coast range from 0 to 4 m/yr. The variability in erosion rates is largely due to differences in the rate of sand supply to the coast, differences in rates of subsidence and human alteration of the shoreline.

One of the more problematic impacts of global climate change is increased frequency and magnitude of severe storms (Elsner et al. 2008; Emanuel, 2005; Webster et al., 2005). While the scientific community is still divided on this issue, studies of the geological record of severe storm impacts indicate no notable variation in storm impacts across the northwestern Gulf of Mexico coast during the past few thousand years (Wallace and Anderson, 2010). In addition, there have been no significant differences in the landfall probabilities between the eastern and western Gulf of Mexico, suggesting that storm steering mechanisms have not varied during this time.

Texas is currently experiencing extended droughts, which severely impacts our water supplies, landscape, and economy. Here again, there are lessons to be learned from geological history. Paleoclimate records from around the state reveal a history of climate variability between warm/dry and cool/wet cycles that reflect natural climate variability over millennial time scales. There is a dire need for additional research to understand the natural climate variability along the upper Texas coast to test numerical models for predicting climate change in the region.

The acceleration of sea-level rise, coupled with minimal sediment supply to the coast, has resulted in increased rates of coastal erosion, both along the Gulf Coast and within bays, and loss of wetlands (Morton et al., 2006; Paine et al., 2012). Thus, the first line of defense against storm surge in more inland areas is being removed. At the same time, the population of the greater Houston area continues to push south and into areas that are highly vulnerable to storm surge. The highly vulnerable Port of Houston and petrochemical industry at the head of Galveston Bay continues to expand. The City of Galveston refuses to adopt a setback policy for new construction along the Gulf shoreline. We are truly living in a “state of denial.”

The Maeslantkering seagate in the Netherlands. Source: Chron.com.

The Maeslantkering sea gate in the Netherlands, built to prevent a tidal or storm surge from flooding Rotterdam. Former Kemah mayor and other civic leaders in Texas are advocating for the construction of a much larger version of the dike at the mouth of the Houston Ship Channel between Bolivar Peninsula and Galveston Island. Source: Chron.com.

One of the greatest obstacles facing the scientific community is communicating knowledge about global climate change and its impacts to policy makers. In Louisiana, where the problems are more chronic, there is far greater awareness of the issue.
As a result, that state has already developed a comprehensive coastal management plan, which is a requirement for future federal funding related to the BP settlement. The Texas General Land Office has just begun working on a comprehensive coastal management plan, but to date that process has resulted in little more than a color brochure and a long shopping list of projects that require attention. We are far behind in our ability to predict coastal response to global climate change, and this is an essential requirement for a comprehensive coastal management plan. Without a comprehensive plan, there will be less money for research and without research there can be no real comprehensive plan. We must break this cycle.

In the past few years there has been an increased effort on the part of the science community to become better organized, share information about the potential impacts of global climate change on coastal environments, and convey scientific knowledge to policy makers (Anderson, 2013). For the most part, these efforts have failed at the city to the state level. Texas has an outstanding academic knowledge base to provide scientific input to the development of a comprehensive coastal management plan. The most widely published academic coastal scientists have joined together in the “Gulf Coastal Science Consortium” intended to provide scientific information and advise on coastal issues (https:// shellcenter.rice.edu/Content.aspx?id=2147483966). To date, there has been minimal effort on the part of the General Land Office of Texas to seek input from its leading coastal scientists in preparing a comprehensive coastal management plan. We need to continue to explore ways to inform policy makers about the realities of global climate change, its ongoing impact on our coast, and potential environmental and socio-economic impacts of continued denial of these issues. We owe it to future generations.

Editor’s Note: This article was first published in Cite, a quarterly magazine by the Rice Design Alliance, and will soon be featured on their website, OffCite. Gracious thanks to the Rice Design Alliance for allowing the re-posting of this article in Climate Change National Forum.

REFERENCES

Anderson, J.B., 2007. The Formation and Future of the Upper Texas Coast. Texas A&M Press, College Station, Texas.

Anderson, J.B., 2013. Coastal Processes and Environments Under Sea-Level Rise and Changing Climate: Science to Inform Management. GSA Today, 23, p. 13-14.
Anderson, J.B., Rodriguez, A.B. (Eds.), 2008. Response of Upper Gulf Coast Estuaries to Holocene Climate Change and Sea-Level Rise. Geological Society of America Special Paper 443, 146 pp.

Carlson, A. E., 2011. Ice Sheets and Sea Level in Earth’s Past. Nature Education Knowledge 3, 3.

Church, J. A., White, N. J., 2011. Sea-level rise from the late 19th to the early 21st century. Surveys in Geophysics 32, 585–602.

Elsner, J.B., Jagger, T.H., and Liu, K.B., 2008b. Comparison of hurricane return levels using historical and geological records. Journal of Applied Meteorology and Climatology, 47, 368–374.

Emanuel, K., 2005. Increasing destructiveness of tropical cyclones over the past 30 years. Nature, 436, 686–688.

Milliken, K.T., Anderson, J.B., and Rodriguez, A.B., 2008a. A new composite Holocene sea-level curve for the northern Gulf of Mexico. In:

Anderson, J.B., Rodriguez, A.B. (Eds.), Response of Upper Gulf Coast Estuaries to Holocene Climate Change and Sea- Level Rise. Geological Society of America Special Paper 443, p. 1-11.

Morton, R.A., Bernier, J.C., Barras, J.A., 2006. Evidence of regional subsidence and associated interior wetland loss induced by hydrocarbon production, Gulf Coast region, USA. Environmental Geology 50, 261–274.

Paine, J.G., 1993. Subsidence of the Texas coast: inferences from historical and late Pleistocene sea levels. Tectonophysics 222, 445–458.

Paine, J.G., Sojan, M. Tiffany, C., 2012. Historical shoreline change through 2007, Texas Gulf Coast: rates contribut- ing causes, and Holocene context. Gulf Coast Association of Geological Societies Journal 1, 13-26.

Rahmstorf, S., Cazenave, A., Church, J.A., Hansen, J.E., Keeling, R.F., Parker, D.E., Somerville, R.C.J., 2007. Recent cli- mate observations compared to projections. Science 316, 709.

Rignot, E., Velicogna, I., van den Broeke, M.R., Monaghan, A., Lenaerts, J.T.M., 2011. Acceleration of the contri- bution of the Greenland and Antarctic ice sheets to sea level rise. Geophysical Research Letters 38, L05503, doi:10.1029/2011GL046583.

Rodriguez, A.B., Anderson, J.B., Siringan, F.P., and Taviani, M.,2004, Holocene evolution of the east Texas coast and inner continental shelf: along-strike variability in coastal retreat rates, Journal of Sedimentary Research, v. 74, p. 406-422.

Wallace, D.J., Anderson, J.B., 2010. Evidence of similar proba- blility of intense hurricane strikes for the Gulf of Mexico over the late Holocene. Geology 38, 511–

Webster, P.J., Holland, G.J., Curray, J.A., and Chang, H.R., 2005, Changes in tropical cyclone number, duration, and intensity in a warming environment. Science, 309, 1844–1846.

Surfside Beach, Texas (6/8/2014) by Tony Kamel. Used courtesy of creator. All rights reserved.

Surfside Beach, Texas (6/8/2014) by Tony Kamel. Used courtesy of creator. All rights reserved.

THE FORUM'S COMMENT THREAD

  • I’d like you to clarify “The only mechanisms that can cause such a rapid increase in the rate of sea-level rise are heating and expansion of the oceans and melting of glaciers and ice sheets; both are known to be occurring at unprecedented rates.”

    First, what’s the scope of “unprecedented”? Presumably, since sea levels were rising at a similar rate 7,000 years ago, expansion and/or melting were proceeding at a similar rate too.

    Second, in principle aquifer depletion could cause sea level rise of the observed magnitude, too. Doesn’t it come down to comparing specific measurements and estimates for the contributions from the various sources?

    • I might be showing my ignorance here, but what’s the mechanism for aquifer depletion leading to sea level rise? Is is just increased land subsidence?
      (In the interest of CCNF’s mission of showing what real scientific discourse is like, I’m doing what I normally do when a colleague says something which sounds like something I’m supposed to already know: I’m asking the question … but usually the internet isn’t watching while I do it!)

      • Sean –
        That’s okay. It’s important for the public to know that scientists don’t pretend to know everything.

        Aquifer depletion means water that used to be underground is no longer underground. That water must now be somewhere else. Since the capacity of the atmosphere to store water is extremely limited, the water that used to be underground ends up in the ocean.

        If an aquifer is used sustainably, so that it is recharged as quickly as it’s used, the overall amount of water underground doesn’t change.

  • One of the most visible aspects of sea level rise on the east coast is the number of beaches that have been and are being renourished. We are spending billions on beach renourishment , which is no surprise to geologists examining the issue, but still most people are unaware of this current cost of climate change.

    We have sufficient measurements of glacier mass balance on alpine glaciers, and with GRACE on the ice sheets to quantify the increasing role of melting glacier ice. GRACE can also measure aquifer depletion of course. This year in the section on alpine glaciers I write for BAMS State of the Climate it is the 23rd consecutive year of mass balance losses.

  • I’m working with a small community in coastal Massachusetts on adapting to sea level rise, and much of what is written here still rings true 2000 miles away. Thanks for a nice article, John. I think our state government in Massachusetts — and most of our local governments — are on board with the reality of the situation, and are ready to listen to and support fact-based coastal planning. So, in that sense, maybe we’re in a better position than what you describe in Texas. As a local group, however, we also need to work right at ground level with the individual property owners. Many of these people feel the threat of climate change very acutely, and too commonly feel “these government scientists” are part of the threat instead of part of the solution, especially when some of our proposed solutions involve personal sacrifice on their part. For people who are scared to lose all they have, even the very communities they love, it’s a real trick to convince them that we are actually on their side. Maybe we could learn something from how our medical colleagues convince a patient to accept a course of treatment which may be more painful than the disease in the short term.

  • John Anderson

    Here are my responses to your comments

    1. By unprecedented I am referring to rates of the past few thousand years. It is well known that prior to this time shrinking ice sheets were the main contributor to sea level rise. In fact, the total rise in sea level that was due mainly to shrinking ice sheets was ~120 meters over the past 17,000 years. Until recently, the contribution of ice sheets to sea-level rise remained unknown and is still debated, but the current acceleration of sea-level rise is attributed to heating of the oceans and melting of land glaciers which is supported by measurements of ocean temperatures and the behavior of mountain glaciers, the vast majority of which are retreating or exhibit signs of instability. With this said, ice sheets are by far the largest potential contributor to sea-level rise. The Antarctic Ice Sheet currently holds the equivalent of 60 meters of sea-level rise in its massive ice sheet, so even minor fluctuations in its mass are important.

    2. As for the groundwater contribution to sea-level rise, this is a potential contributor, but a very hard one to assess. Hence there is debate about the magnitude of groundwater depletion on a global scale. With this said, scientists have have attempted to estimate the contributions from observed warming of the oceans and mountain glaciers and these contributions are large enough to explain most of the observed acceleration.

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PUBLIC COMMENT THREAD

  • http://atmo.tamu.edu/profile/JNielsen-Gammon John Nielsen-Gammon

    I’d like you to clarify “The only mechanisms that can cause such a rapid increase in the rate of sea-level rise are heating and expansion of the oceans and melting of glaciers and ice sheets; both are known to be occurring at unprecedented rates.”

    First, what’s the scope of “unprecedented”? Presumably, since sea levels were rising at a similar rate 7,000 years ago, expansion and/or melting were proceeding at a similar rate too.

    Second, in principle aquifer depletion could cause sea level rise of the observed magnitude, too. Doesn’t it come down to comparing specific measurements and estimates for the contributions from the various sources?

    • http://web.mit.edu/physics/people/academic/robinson_sean.html Sean Robinson

      I might be showing my ignorance here, but what’s the mechanism for aquifer depletion leading to sea level rise? Is is just increased land subsidence?
      (In the interest of CCNF’s mission of showing what real scientific discourse is like, I’m doing what I normally do when a colleague says something which sounds like something I’m supposed to already know: I’m asking the question … but usually the internet isn’t watching while I do it!)

      • http://atmo.tamu.edu/profile/JNielsen-Gammon John Nielsen-Gammon

        Sean –
        That’s okay. It’s important for the public to know that scientists don’t pretend to know everything.

        Aquifer depletion means water that used to be underground is no longer underground. That water must now be somewhere else. Since the capacity of the atmosphere to store water is extremely limited, the water that used to be underground ends up in the ocean.

        If an aquifer is used sustainably, so that it is recharged as quickly as it’s used, the overall amount of water underground doesn’t change.

  • http://glacierchange.wordpress.com/ Mauri Pelto

    One of the most visible aspects of sea level rise on the east coast is the number of beaches that have been and are being renourished. We are spending billions on beach renourishment , which is no surprise to geologists examining the issue, but still most people are unaware of this current cost of climate change.

    We have sufficient measurements of glacier mass balance on alpine glaciers, and with GRACE on the ice sheets to quantify the increasing role of melting glacier ice. GRACE can also measure aquifer depletion of course. This year in the section on alpine glaciers I write for BAMS State of the Climate it is the 23rd consecutive year of mass balance losses.

  • http://web.mit.edu/physics/people/academic/robinson_sean.html Sean Robinson

    I’m working with a small community in coastal Massachusetts on adapting to sea level rise, and much of what is written here still rings true 2000 miles away. Thanks for a nice article, John. I think our state government in Massachusetts — and most of our local governments — are on board with the reality of the situation, and are ready to listen to and support fact-based coastal planning. So, in that sense, maybe we’re in a better position than what you describe in Texas. As a local group, however, we also need to work right at ground level with the individual property owners. Many of these people feel the threat of climate change very acutely, and too commonly feel “these government scientists” are part of the threat instead of part of the solution, especially when some of our proposed solutions involve personal sacrifice on their part. For people who are scared to lose all they have, even the very communities they love, it’s a real trick to convince them that we are actually on their side. Maybe we could learn something from how our medical colleagues convince a patient to accept a course of treatment which may be more painful than the disease in the short term.

  • John Anderson

    Here are my responses to your comments

    1. By unprecedented I am referring to rates of the past few thousand years. It is well known that prior to this time shrinking ice sheets were the main contributor to sea level rise. In fact, the total rise in sea level that was due mainly to shrinking ice sheets was ~120 meters over the past 17,000 years. Until recently, the contribution of ice sheets to sea-level rise remained unknown and is still debated, but the current acceleration of sea-level rise is attributed to heating of the oceans and melting of land glaciers which is supported by measurements of ocean temperatures and the behavior of mountain glaciers, the vast majority of which are retreating or exhibit signs of instability. With this said, ice sheets are by far the largest potential contributor to sea-level rise. The Antarctic Ice Sheet currently holds the equivalent of 60 meters of sea-level rise in its massive ice sheet, so even minor fluctuations in its mass are important.

    2. As for the groundwater contribution to sea-level rise, this is a potential contributor, but a very hard one to assess. Hence there is debate about the magnitude of groundwater depletion on a global scale. With this said, scientists have have attempted to estimate the contributions from observed warming of the oceans and mountain glaciers and these contributions are large enough to explain most of the observed acceleration.

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