BACKGROUND:Although thermal expansion of seawater and melting of mountain glaciers have dominated global mean sea level (GMSL) rise over the last century, mass loss from the Greenland and Antarctic ice sheets is expected to exceed other contributions to GMSL rise under future warming. To better constrain polarice-sheetresponse to warmer temperatures, we draw on evidence from in- terglacial periods in the geologic record that ex- perienced warmer polar temperatures and higher GMSLs than present. Coastal records of sea level from these previous warm periods dem- onstrate geographic variability because of the influence of several geophysical processes that operate across a range of magnitudes and time scales. Inferring GMSL and ice- volume changes from these reconstructions is nontrivial and generally requires the use of geophysical models. ADVANCES: Interdisciplinary studies of geo- logic archives have ushered in a new era of deciphering magnitudes, rates, and sources of sea-level rise. Advances in our understanding of polar ice-sheet response to warmer climates have been made through an increase in the number and geographic distribution of sea- level reconstructions, better ice-sheet constraints, and the recognition that several geophysical processes cause spatially complex patterns in sea level. In particular, accounting for glacial isostatic processes helps to decipher spatial variability in coastal sea-level records and has reconciled a number of site-specific sea-level reconstructions for warm periods that have oc- curred within the past several hundred thou- sand years. This enables us to infer that during recent interglacial periods, small increases in

/pdf/sea-level-rise-due-to-polar-ice-sheet-mass-loss-during-past-53ct5yql0u.pdf

Sea-level rise due to polar ice-sheet mass loss during past warm periods

The reliability of Arctic climate predictions is currently hampered by insufficient knowledge of natural climate variability in the past. A sediment core from Lake El'gygytgyn in northeastern (NE) ...

/pdf/2-8-million-years-of-arctic-climate-change-from-lake-el-300swm9f10.pdf

2.8 Million Years of Arctic Climate Change from Lake El’gygytgyn, NE Russia

Interglacials, including the present (Holocene) period, are warm, low land ice extent (high sea level), end-members of glacial cycles. Based on a sea level definition, we identify eleven interglacials in the last 800,000 years, a result that is robust to alternative definitions. Data compilations suggest that despite spatial heterogeneity, Marine Isotope Stages (MIS) 5e (last interglacial) and 11c (~400 ka ago) were globally strong (warm), while MIS 13a (~500 ka ago) was cool at many locations. A step change in strength of interglacials at 450 ka is apparent only in atmospheric CO2 and in Antarctic and deep ocean temperature. The onset of an interglacial (glacial termination) seems to require a reducing precession parameter (increasing Northern Hemisphere summer insolation), but this condition alone is insufficient. Terminations involve rapid, nonlinear, reactions of ice volume, CO2, and temperature to external astronomical forcing. The precise timing of events may be modulated by millennial-scale climate change that can lead to a contrasting timing of maximum interglacial intensity in each hemisphere. A variety of temporal trends is observed, such that maxima in the main records are observed either early or late in different interglacials. The end of an interglacial (glacial inception) is a slower process involving a global sequence of changes. Interglacials have been typically 10–30 ka long. The combination of minimal reduction in northern summer insolation over the next few orbital cycles, owing to low eccentricity, and high atmospheric greenhouse gas concentrations implies that the next glacial inception is many tens of millennia in the future.

/pdf/interglacials-of-the-last-800-000-years-4z2p0npwhb.pdf

Interglacials of the last 800,000 years

Varves in lake sediments – a review

Understanding the evolution of Arctic polar climate from the protracted warmth of the middle Pliocene into the earliest glacial cycles in the Northern Hemisphere has been hindered by the lack of co ...

https://www.geo.umass.edu/climate/papers2/BrighamGrette_Science2013.pdf

Pliocene Warmth, Polar Amplification, and Stepped Pleistocene Cooling Recorded in NE Arctic Russia

Between October 2008 and May 2009, the International Continental Scientific Drilling Program (ICDP) co-sponsored a campaign at Lake Elgygytgyn, located in a 3.6-Ma-old meteorite impact crater in northeastern Siberia. Drilling targets included three holes in the center of the 170-m-deep lake, utilizing the lake ice cover as a drilling platform, plus one hole close to the shore in the western lake catchment. At the lake's center. the entire 315-m-thick lake sediment succession was penetrated. The sediments lack any hiatuses (i.e., no evidence of basin glaciation or desicca- tion), and their composition reflects the regional climatic and environmental history with great sensitivity. Hence, the record provides the first comprehensive and widely time- continuous insights into the evolution of the terrestrial Arctic since mid-Pliocene times. This is particularly true for the lowermost 40 meters and uppermost 150 meters of the sequence, which were drilled with almost 100% recovery and likely reflect the initial lake stage during the Pliocene and the last ~2.9 Ma, respectively. Nearly 200 meters of under- lying rock were also recovered; these cores consist of an almost complete section of the various types of impact brec- cias including broken and fractured volcanic basement rocks and associated melt clasts. The investigation of this core sequence promises new information concerning the Elgygytgyn impact event, including the composition and nature of the meteorite, the energy released, and the shock behavior of the volcanic basement rocks. Complementary information on the regional environmental history, including the permafrost history and lake-level fluctuations, is being developed from a 142-m-long drill core recovered from the permafrost deposits in the lake catchment. This core con- sists of gravelly and sandy alluvial fan deposits in ice-rich permafrost, presumably comprising a discontinuous record of both Quaternary and Pliocene deposits.

/pdf/the-lake-el-gygytgyn-scientific-drilling-project-conquering-3ei72s7ih3.pdf

Eeva Haltia-Hovi

Papers

2.8 Million Years of Arctic Climate Change from Lake El’gygytgyn, NE Russia

The Lake El'gygytgyn Scientific Drilling Project -Conquering Arctic Challenges through Continental Drilling