TY - JOUR

T1 - Evolution of mean ocean temperature in Marine Isotope Stage 4

AU - Shackleton, Sarah

AU - Menking, James A.

AU - Brook, Edward

AU - Buizert, Christo

AU - Dyonisius, Michael N.

AU - Petrenko, Vasilii V.

AU - Baggenstos, Daniel

AU - Severinghaus, Jeffrey P.

PY - 2021/10/27

Y1 - 2021/10/27

N2 - Deglaciations are characterized by relatively fast and near-synchronous changes in ice sheet volume, ocean temperature, and atmospheric greenhouse gas concentrations, but glacial inception occurs more gradually. Understanding the evolution of ice sheet, ocean, and atmosphere conditions from interglacial to glacial maximum provides insight into the interplay of these components of the climate system. Using noble gas measurements in ancient ice samples, we reconstruct mean ocean temperature (MOT) from 74 to 59.7 ka, covering the Marine Isotope Stage (MIS) 5a-4 boundary, MIS 4, and part of the MIS 4-3 transition. Comparing this MOT reconstruction to previously published MOT reconstructions from the last and penultimate deglaciation, we find that the majority of the last interglacial-glacial ocean cooling must have occurred within MIS 5. MOT reached equally cold conditions in MIS 4 as in MIS 2 (-2.7 +/- 0.3 degrees C relative to the Holocene, -0.1 +/- 0.3 degrees C relative to MIS 2). Using a carbon cycle model to quantify the CO2 solubility pump, we show that ocean cooling can explain most of the CO2 drawdown (32 +/- 4 of 40 ppm) across MIS 5. Comparing MOT to contemporaneous records of benthic delta O-18, we find that ocean cooling can also explain the majority of the delta O-18 increase across MIS 5 (0.7 parts per thousand of 1.3 parts per thousand). The timing of ocean warming and cooling in the record and the comparison to coeval Antarctic isotope data suggest an intimate link between ocean heat content, Southern Hemisphere high-latitude climate, and ocean circulation on orbital and millennial timescales.

AB - Deglaciations are characterized by relatively fast and near-synchronous changes in ice sheet volume, ocean temperature, and atmospheric greenhouse gas concentrations, but glacial inception occurs more gradually. Understanding the evolution of ice sheet, ocean, and atmosphere conditions from interglacial to glacial maximum provides insight into the interplay of these components of the climate system. Using noble gas measurements in ancient ice samples, we reconstruct mean ocean temperature (MOT) from 74 to 59.7 ka, covering the Marine Isotope Stage (MIS) 5a-4 boundary, MIS 4, and part of the MIS 4-3 transition. Comparing this MOT reconstruction to previously published MOT reconstructions from the last and penultimate deglaciation, we find that the majority of the last interglacial-glacial ocean cooling must have occurred within MIS 5. MOT reached equally cold conditions in MIS 4 as in MIS 2 (-2.7 +/- 0.3 degrees C relative to the Holocene, -0.1 +/- 0.3 degrees C relative to MIS 2). Using a carbon cycle model to quantify the CO2 solubility pump, we show that ocean cooling can explain most of the CO2 drawdown (32 +/- 4 of 40 ppm) across MIS 5. Comparing MOT to contemporaneous records of benthic delta O-18, we find that ocean cooling can also explain the majority of the delta O-18 increase across MIS 5 (0.7 parts per thousand of 1.3 parts per thousand). The timing of ocean warming and cooling in the record and the comparison to coeval Antarctic isotope data suggest an intimate link between ocean heat content, Southern Hemisphere high-latitude climate, and ocean circulation on orbital and millennial timescales.

KW - MERIDIONAL OVERTURNING CIRCULATION

KW - SEA-LEVEL

KW - GLACIAL MAXIMUM

KW - ICE VOLUME

KW - CLIMATE

KW - RECORD

KW - CARBON

KW - ATLANTIC

KW - DELTA-O-18

KW - GASES

U2 - 10.5194/cp-17-2273-2021

DO - 10.5194/cp-17-2273-2021

M3 - Journal article

VL - 17

SP - 2273

EP - 2289

JO - Climate of the Past

JF - Climate of the Past

SN - 1814-9324

IS - 5

ER -