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Hurricanes: How Big is BIG and how do we know? (gr 6-8)
Author Information
* Name: Jared Friedman (Masters Student), Dr. Emily Elliott (Assistant Professor), Jessica Laura (Undergraduate Student at Cal Poly San Luis Obispo)
* Affiliation: Department of Geography/New College, University of Alabama
Contact Information (Email, Twitter, Personal Website, etc.):
* Contact: Jmfriedman4 [at] crimson.ua.edu
@palmsarenttrees
* Year contributed: 2023
Categories
- Grade Level: grades 6 - 8
- Alabama Course of Study:
SCI.6.4.4 SCI.6.5.4 SCI.6.7.5
Abstract
Scientists believe that hurricanes are getting more intense as a result of climate change, but we need a strong record to compare modern data to these historic hurricanes. Prior to 1970, most of our hurricane records are based on observation, so are extremely unreliable. In order to try better understand hurricanes of the past, we combine natural records from the environment (i.e. tree-rings, sediments, corals, cave samples), which we call proxy records, to naturally record what is occurring in the environment over time. Not all proxy records are the same, as they vary on the time-scales they record and what they indicate about a record through time. It is important to understand what each proxy is indicating about the environment to select for the most effective ways to build certain periods of time in our dataset.
On the beach during a hurricane, sediment can ‘washover’ from the shoreface oceanside of the beach to the backshore into marshes or the back-barrier estuarine environment. This can leave behind coastal deposits/landforms known as overwash/overwash fans. Sediment cores of overwash deposits give us a good idea of hurricane intensity, as increases in wave energy from hurricane storm surge brings increased coarse sediment into the deposit. By understanding how different modern storm intensities and the sediment it brings to the overwash deposit it is possible to investigate the past and determine storm intensity from these overwash sediment proxy records.
Likewise, as trees grow, they record annual records of what is occurring in the area they are growing. By analyzing a trees-rings, it is possible to determine annually a record of storms, environmental conditions, among many other things. Tree-rings can give us precise dates, they record increased precipitation in the form of wider tree-rings in a given year, different seasonal changes in growth depending on the width of the ‘early’ or ‘late’ part of the rings growth in a given year, and trees can even record evidence of stressful events in their rings through changes in the rings structure through anatomical anomalies called “false rings.” In terms of hurricanes, tree-rings records can give a good indication of the overall regional hurricane frequency on an annual basis.
Different records can tell us different things and on different timescales. For hurricanes, we call proxy records ‘tempestites’ or storm records. Sediment tempestite records are good indicators of how ‘big’ the hurricane is in a specific area, and can record 1000’s of years, but are not very good at recording how often, the overall frequency, of when hurricanes occur. Tree-ring tempestite records on the other hand do a very good job of recording annual records of hurricane occurrence over a larger area but are limited by how long the tree can live (usually 100-500 yrs.) and cannot tell us about how intense a hurricane was over time. By combining these tempestite proxy records we aim to extend our current record of hurricanes back hundreds, potentially thousands of years. Through this combined record it is possible to get an overall understanding of both the frequency and intensity of hurricanes through time, ultimately helping us to understand how often big hurricanes have occurred in the past and helping us to better understand how climate change may impact hurricanes in the future.
