Senior Theses 2003
Jenna LoDico (2003). Multi-proxy approach to distinguish
between past changes in sea surface temperature and melt water
input in the Gulf of Mexico
Faculty advisor: David Hastings
The Gulf of Mexico is part of the Western Hemisphere Warm Pool (WHWP) providing a source of heat and moisture to the North American continent and Northern high latitudes. In this thesis I am presenting paleoclimatic records from the Gulf of Mexico (GOM) which test the hypothesis that the tropical climate system is an important driver of past global climate change. Core MD02-255I from OrcaBasin situated in the northern GOM (26°56. 78'N 91°21.75') was recovered with 31.79 m of sediment. I present a multi-proxy approach using Mg/Ca and from foraminiferal calcite to determine past sea surface temperature (SST) and of sea water.
From.42.1 to 25 kyr BP SSTs indicated by white and pink Globigerinoides ruber range from low of 22.1 (± 0.2) °C and 23.3 (± 0.2) °C to highs of 26.3 (± 0.8) °C and 26.2 (± 0.06) respectively. The mean SST from 42.1 to 25 kyr BP based on white G. ruber is 23.8(± 0.l) and from pink 24.6(± 0.2) °c. During MIS 2 from 25 to 12 kyr BP the average SSTs for white G. ruber are 24.8 (± 0.2) °C and based on pink are 25.1 (± 0.2) °C. Average mean values during late Holocene based on both white and pink are 27.5 (± 0.2) °C, which is in agreement with modem day values for GOM. SSTs during glacial toInterglacial, varied by as much as 5.1 (± 0.3) °C, based on both white and pink G. ruber. This is significantly higher than previous estimates from CLIMAP (1976). Mid-Marine Isotope Stage Three (MIS 3) based on white G. ruber indicates a mean value of about 1.8 ‰ and pink indicate 1.1 ‰ (high variability of > 0.5 ‰). Both white and pink G. ruber for show a mean value of about 1.0 ‰ at the Last Glacial Maximum (low variability of < 0.5 ‰) and also indicate a mean value of about -1.3 ‰ during the Holocene (low variability of < 0.5 ‰)' The relationship between changing GOM SSTs and melt water input from the Laurentide Ice Sheet is evident from a sharp decrease in the of seawater at 12 kyr, which is preceded by a warming indicated by both white and pink of 3 ± (0.4 ) °C from 17.8 to 15.4 kyr BP. The record of GOM SSTs and of seawater show that the subtropics underwent a significant change from the last glacial maximum to the current interglacial.
PURPOSE OF PROJECTThe primary objective of this project is to create a record of sea surface temperatures (SSTs) from OrcaBasin in Gulf of Mexico from foraminiferal Mg/Ca from 42 kyr BP to the present. A second objective is to create a curve indicating salinity and ice volume from foraminiferal tests. Mg/Ca and were generated from the planktonic foraminifera Globigerinoides ruber. By using a multi-proxy approach I will be able to distinguish between the changes in sea surface temperatures and melt water input into the Gulf of Mexico up to mid-Marine Isotope Stage Three (MIS 3). By using Mg/Ca and from foraminiferal calcite past SSTs and (controlled by temperature, salinity and ice volume) can be separated. Isolating temperature will help establish the relationship between changing Gulf of Mexico SSTs and melt water input from the Laurentide Ice Sheet. This record will also be able to be compared with other paleoclimate records such as GISP2 (Greenland) and Byrd (Antarctica) ice core records. This will help clarify the relationship between subtropical changes in SST and the relationship to changes in Greenland and Antarctic air temperatures. Ideally, these data will provide insight into the role of the tropical climate system on global climate change.