The Enigma of Marine Isotope Stage 4 (MIS4) Compared to MIS2 in the Arctic Ocean
Abstract
Examination of both the coarse (>250microns) ice-rafted debris (IRD) and the sources of this IRD in cores from the western Arctic and Fram Strait that contain both MIS2 and MIS4 show nearly equal or even greater IRD in MIS4 than MIS2. The quantities of ice-rafted Fe grains in the sand fraction of these cores from known areas of glacial outlets and iceberg calving show the same pattern of greater amounts during MIS4 compared to MIS2. These Fe grains are matched to specific source areas around the periphery of the Arctic Ocean using the chemical fingerprint of 14 elements in each of about 100 Fe grains from each core sample matched to similar microprobe analyses of Fe grains from all potential circum-Arctic sources. This is an enigma because MIS4 is considered less intense cold glacial interval than MIS2, thus more IRD would be expected for the latter. If this anomaly is due to warmer summer conditions in the western and central Arctic Ocean during MIS4 and thus greater melt-out in these areas, then the same must be true for Fram Strait, the site of one of the studied cores. Yet Fram Strait was interpreted as being nearly ice free even during most of MIS2, at least near the Yermak Plateau (the site of one of our studied cores), allowing warm surface water to enter the Arctic. Also important is the occurrence of more IRD during MIS2, 3, and 4 than in MIS1. If melt-out rates were higher in the central Arctic during MIS4 than in MIS2, then why the lower IRD amounts during MIS1, a known interval of warmer summers in the Arctic? Regardless of whether there were warmer conditions in the Arctic for MIS4 compared to MIS2, the abundance of IRD during MIS4 is clearly anomalous considering that this stage is interpreted as a less intense glacial throughout the sub-Arctic compared to MIS2.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP31F1724D
- Keywords:
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- 4914 Continental climate records;
- PALEOCEANOGRAPHYDE: 4926 Glacial;
- PALEOCEANOGRAPHYDE: 4946 Milankovitch theory;
- PALEOCEANOGRAPHYDE: 4954 Sea surface temperature;
- PALEOCEANOGRAPHY