The Last Interglacial in the Central North Atlantic as Shown by Foraminiferal Abundance Amanda Perrone, Hofstra University GES; Rania Khan, Sewanhaka High School; George Paraskevas, Hofstra University Engineering; E. Christa Farmer, Hofstra University GES; Jerry McManus, LDEO of CU; Yuxin Zhou, UCSB; Erin Walsh, H. Frank Carey High School in Franklin Square, NY; Anthony Johnson, Triumvirate Environmental, Queens, NY; Sela Lewis, Washington University, St. Louis, MO; Kshan Pandey, East Meadow High School
Results: Introduction:
When was the last interglacial period? The last interglacial began about 127,000 years ago, and the last interglacial maximum is also known as the Eemian (Shackleton, 1969). Why do we study the last interglacial? This is the most recent time for when temperatures are the most like the present. Studying how sea-surface temperature (SST) has varied in the past helps us to understand the Earth’s natural response to climate change. What are we studying here? Marine Isotope Stage (MIS) 5 covers the entire last interglacial period and is divided into 5 parts to differentiate the smaller magnitude warming and cooling trends (Shackleton, 1969). These sections are referred to as MIS 5a-e and are defined by their peaks. The Eemian is categorized as MIS 5e. The foraminifera species Neogloboquadrina pachyderma (figure 3) can be used to plot SST since the percentage of N. pachyderma found increases as the water gets colder while the percentage of N. incompta (figure 4) decreasing proportionally (Darling et al., 2006). The question we are answering here is: Does our data
correspond with 5 substages in MIS 5?
Figure 1: IODP drilling ship, JOIDES Resolution.
• Our N. pachyderma % data has more fluctuations than the Smith et al. data. • Peaks in N. pachyderma % generally coincide with the MIS peaks and fit similar fluctuation patterns to the ∂18O data. • The MIS substage peak appears slightly younger than the regional peaks in ∂18O.
• Samples were collected by the JOIDES Resolution off the coast of the Azores in the North Atlantic Ocean (Figure 1, Figure 5). • From a representative sample, the percentage of N. pachyderma is calculated from dividing the total count of planktonic foraminifera by the amount of N. pachyderma identified. • Using age and meters composite depth (MCD) data within the IODP report (Expedition 336 Scientists, 2013), I plotted a line of best fit for the ages at the MCDs our samples cover. • From there, I used the MIS boundaries dataset (Lisiecki & Raymo, 2004) and the line of best fit equation to calculate the MCD within U1313 samples that would correspond to the MIS boundaries.
samples and plots the peaks of each MIS 5 substage.
MIS 5 Peaks of IODP Site U1313 Smith et al. N. pachyderma %
4.24
4.74
5.24
5.74
6.24 -10 -8
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MIS Substage Peaks
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Figure 4:
N. Incompta Sample from MCD 4.62.
Future outcomes: As more samples are picked and more N. pachyderma% data is collected, we can piece together a better idea for the millennial cycles within MIS 5 and other MIS stages. With more data points in MIS 5, perhaps more definitive substage boundaries can be created.
We gratefully acknowledge support for this research from National Science Foundation Award #1911514, the Hofstra University Faculty Research and Development Fund and the Hofstra University Rabinowitz Honors College Research Assistant Program. Thank you to the IODP for collecting the samples. We appreciate the contributions of the Hofstra University GEOL135 Sedimentation class of Fall 2021, and the GEOL140 Paleoclimatology class of Spring 2022, who also worked on this dataset. Thank you to Jason Williams for teaching us how to use the SEM!
References:
-4
N. pachyderma %
∂18O (‰)
0
What does our data tell us? Compared to the data from Smith et al. 2013, we have a higher resolution in our data. A higher resolution has the potential to hint at the millennial cycles to come due to natural climate change. The slight deviance between the MIS substage peaks and the ∂18O data could be because the MIS dataset is determined through global benthic foraminifera data rather than the local planktonic foraminifera data (Lisiecki & Stern, 2016).
Acknowledgments:
HU N. pachyderma %
Meters Composite Depth 3.74
N. pachyderma sample from MCD 4.62.
Discussion:
Methods:
Figure 2: This graph compares the faunal data collected to the ∂18O and the faunal data from other U1313 Smith et al. G. bulloides ∂18O
Figure 3:
- Darling, Kate F., et al. "A resolution for the coiling direction paradox in Neogloboquadrina pachyderma." Paleoceanography 21.2 (2006). - Expedition 306 Scientists, “Site U1313.” Proceedings of the IODP (2006). - Lisiecki, Lorraine E., and Maureen E. Raymo. "A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records." Paleoceanography 20.1 (2005). - Lisiecki, Lorraine E., and Joseph V. Stern. "Regional and global benthic δ18O stacks for the last glacial cycle." Paleoceanography 31.10 (2016): 1368-1394. - Sakaguchi, Arito. “JOIDES Resolution.” joidesresolution.org, 12 November 2012, joidesresolution.org/public/in-search-of-earths-secrets/drill-down-deeper/. - Shackleton, Nicholas John. "The last interglacial in the marine and terrestrial records." Proceedings of the Royal Society of London. Series B. Biological Sciences 174.1034 (1969): 135-154. - Smith, M., et al. "Data report: oxygen isotopes and foraminifer abundance record for the last glacial–interglacial cycle and marine isotope Stage 6 at IODP Site U1313." Proceedings of Integrated Ocean Drilling Program 303.306 (2013): 306.
Figure 5: Map
Showing the location of IODP sediment core site U1313 about 240 miles northwest of the Azores in the North Atlantic. Figure from Expedition 306 Scientists, 2006.