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Abrupt climate changes during the last deglaciation have been well preserved in proxy records across the globe. However, one long-standing puzzle is the apparent absence of the onset of the Heinrich Stadial 1 (HS1) cold event around 18 ka in Greenland ice core oxygen isotope δ 18 O records, inconsistent with other proxies. Here, combining proxy records with an isotope-enabled transient deglacial simulation, we propose that a substantial HS1 cooling onset did indeed occur over the Arctic in winter. However, this cooling signal in the depleted oxygen isotopic composition is completely compensated by the enrichment because of the loss of winter precipitation in response to sea ice expansion associated with AMOC slowdown during extreme glacial climate. In contrast, the Arctic summer warmed during HS1 and YD because of increased insolation and greenhouse gases, consistent with snowline reconstructions. Our work suggests that Greenland δ 18 O may substantially underestimate temperature variability during cold glacial conditions.
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The impact of floating ice on sea level estimates across multiple glacial cycles
Unlike grounded ice sheets, floating ice shelves have minimal direct impact on sea level. However, depending on the method, proxy sea level reconstructions may be affected by the existence of floating ice. Unless ice shelves intercept the seafloor, their former presence is very difficult to detect. The recent discovery of ice erosional features in deep water depths at various locations throughout the Arctic Basin may indicate that extensive ice shelves existed in the Arctic Ocean during glacial maxima. Although dating these features is difficult, the current constraints suggest that a thick ice shelf existed during the penultimate glacial maximum. However, this does not rule out that ice shelves also existed during other glacial stages. Here we use ice sheet and oxygen isotope modeling to explore what impact a former Arctic ice shelf would have on our interpretations of past ice volumes during glacial maxima. We suggest that a former Arctic ice shelf may help to resolve some existing discrepancies between different proxy sea level reconstructions.
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- Award ID(s):
- 1664013
- PAR ID:
- 10113505
- Date Published:
- Journal Name:
- AGU Fall Meeting
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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