Lab 4

OEAS 108N Fall 2023 Understanding Global Climate Change Juli Sprague UIN# 01178616 LAB 4 – Sea Level Rise This lab will be due in Canvas by Sunday September 24, 2023 at 11 AM. As usual, type your answers in the space below each question and add extra spaces as needed (don’t worry about creating any extra pages in your final Word document). Sea level rise is one of the most immediate impacts of climate change, affecting coastlines around the world daily. As the ocean continues to warm and ice melts, sea level will continue to rise with its impacts becoming ever more severe. At the same time other factors also contribute to local changes in sea level. In this lab we will explore some of these factors and examine how the rate of sea level rise itself may have changed over the past century. We will also examine how sea level rise impacts two different, but very vulnerable cities – Norfolk, VA and New Orleans, LA. 1. In Canvas there is an Excel file called “sea level rise”. Download the file and look at the worksheet “GMSL”, which contains estimates of global mean sea level versus time obtained using tide gauge data. Tide gauge records go back into the 19 th century (and at some sites even earlier), although tide gauge records must be carefully corrected for a wide range of factors that can impact calculated rates of sea level rise. a . [ 5 points ] Graph A shows how relative mean sea level has varied from ~1880 until ~2013. Does the rate of sea level rise appear to be constant over this time period? Why or why not (based simply looking at this graph)? Note that you will come back and re-examine your answer here at the end of this question. The rate of sea level appears to be raising at a constant rate, as the points on the graph seem to make a straight line. b . [ 5 points ] Graph B shows a subset of the data in graph A for the time period 1880-1930 (note that the two graphs have been scaled differently). Use the “trend line” function in Excel to calculate the rate of sea level rise over the time period 1880-1930. What is this value (please be sure to include units)? 1.1384 mm/years c. [ 5 points ] Graph C is a subset of the data in graph A for the time period 1930-1980 (again note that the two graphs have been scaled differently). Use the “trend line” function in Excel to calculate the rate of sea level rise over the time period 1930-1980. What is this value (please be sure to include units)? 1

1.7847 mm/years d . [ 5 points ] Now look at graph D which plots a portion of the tide gauge data in Graph A from 1990-2013, and again use the “trend line” function in Excel to calculate the rate of sea level rise over this time period. What is the rate of sea level rise (again with proper units) during this time period? 3.299 mm/years e . [ 10 points ] Hopefully you saw that the rate of sea level rise has been increasing over time from 1880-2013 (i.e., sea level rise (1880-1930) < sea level rise (1930-1980) < sea level rise (1990-2013)). If this is not what you saw, go back and check your work. What might be causing this acceleration in the rate of sea level rise since 1880? (Hint: you may want to go back and look at material discussed in ch. 2 of your textbook). The rise in sea level is likely due to a rise in temperature, causing ice to melt. f . [ 3 points ] Is you answer to part e consistent with your answer to part a ? It should be, and if it is not, please go back and look at your answer to part a and adjust your answer accordingly. My answer to part e is consistent to my answer to part a, both show that the sea level rises at a constant rate. 2. In the same Excel file there is a second worksheet called “Sewells Point”. The data here comes from Sewells Point on Naval Station Norfolk (for more details see the map below, and https://tidesandcurrents.noaa.gov/stationhome.html?id=8638610 ). Tide gauge data at this site goes back to 1927 although here we only show data from 1928 until 1980 (relative to an average value of sea level in 1990). a . [ 5 points ] Using the graph on this page calculate the rate of sea level rise at Sewells Point 2

Overall, the amount of useable land decreases as the sea level rises. b. [ 5 points ] At what water level (i.e., amount of sea level rise) will Hampton Blvd. in front of the football stadium be under water? At around 6.5 ft underwater, Hampton Blvd. in front of the football stadium will be under water. c. [ 10 points ] List five ways your life would be different if the water level around Norfolk were to rise 10 feet? To answer this question, you may want to zoom the map out and look at the overall impact of sea level rise on the area. At 10 ft under water, a large portion of Southeast Virginia is underwater, so it would be nearly impossible for anyone to live around here. 5. a. [ 10 points ] Now search for New Orleans, LA, in the upper right corner of this web page. What does the map of New Orleans look like with 1 foot of sea level rise? What about 10 feet? At 1 ft of sea level rise, nearly all of the land outside of New Orlean’s levee is under water. Even while being 10 feet below sea level, the heart of New Orleans is still protected from drowning by the levees. b. [ 5 points ] On the far left of this page is a box labelled “Change Other Settings.” It should be set on “Exclude all potentially protected areas” (if not set it so this selected). Now set the water level to 10 ft and toggle between “Exclude all potentially protected areas” and “All land below water level”. Hopefully you will see a dramatic difference in the map of New Orleans and the surrounding areas for these two different settings. Why is this the case? When in the “exclude all potentially protected areas” setting, much of New Orleans is dry even when the water level is set to 10 ft. However, once the setting is changed to “all land below water 4

level, the entirety of New Orleans is shown to be under water. 6. [ 10 points ] How do these observations about sea level rise in New Orleans compare with those for Norfolk? Here you may want to go back to the map of Norfolk, raise the water level and toggle these same choices under “Change Other Settings.” What does this tell us about differences in the potential vulnerability of these cities to sea level rise? At a 10 ft water level, less of Norfolk is underwater than in New Orleans. This shows that the land in Norfolk is at a higher altitude than in New Orleans. 5