We used 5704 14C, 10Be, and 3He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial Maximum (LGM) in terms of global ice-sheet and mountain-glacier extent. Growth of the ice sheets to their maximum positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level ~14.5 ka.

https://science.sciencemag.org/content/sci/325/5941/710.full.pdf

The Last Glacial Maximum.

High-resolution record of Northern Hemisphere climate extending into the last interglacial period

/pdf/high-resolution-record-of-northern-hemisphere-climate-1flrm897o6.pdf

High-resolution record of Northern Hemisphere climate extending into the last interglacial period.

The major cause of sea-level change during ice ages is the exchange of water between ice and ocean and the planet's dynamic response to the changing surface load. Inversion of ∼1,000 observations for the past 35,000 y from localities far from former ice margins has provided new constraints on the fluctuation of ice volume in this interval. Key results are: (i) a rapid final fall in global sea level of ∼40 m in <2,000 y at the onset of the glacial maximum ∼30,000 y before present (30 ka BP); (ii) a slow fall to -134 m from 29 to 21 ka BP with a maximum grounded ice volume of ∼52 × 10(6) km(3) greater than today; (iii) after an initial short duration rapid rise and a short interval of near-constant sea level, the main phase of deglaciation occurred from ∼16.5 ka BP to ∼8.2 ka BP at an average rate of rise of 12 m⋅ka(-1) punctuated by periods of greater, particularly at 14.5-14.0 ka BP at ≥40 mm⋅y(-1) (MWP-1A), and lesser, from 12.5 to 11.5 ka BP (Younger Dryas), rates; (iv) no evidence for a global MWP-1B event at ∼11.3 ka BP; and (v) a progressive decrease in the rate of rise from 8.2 ka to ∼2.5 ka BP, after which ocean volumes remained nearly constant until the renewed sea-level rise at 100-150 y ago, with no evidence of oscillations exceeding ∼15-20 cm in time intervals ≥200 y from 6 to 0.15 ka BP.

/pdf/sea-level-and-global-ice-volumes-from-the-last-glacial-1bjrm4r0m5.pdf

Sea level and global ice volumes from the Last Glacial Maximum to the Holocene.

The last glacial cycle was characterized by substantial millennial-scale climate fluctuations1,2,3,4,5, but the extent of any associated changes in global sea level (or, equivalently, ice volume) remains elusive. Highstands of sea level can be reconstructed from dated fossil coral reef terraces6,7, and these data are complemented by a compilation of global sea-level estimates based on deep-sea oxygen isotope ratios at millennial-scale resolution8 or higher1. Records based on oxygen isotopes, however, contain uncertainties in the range of ±30 m, or ±1 °C in deep sea temperature9,10. Here we analyse oxygen isotope records from Red Sea sediment cores to reconstruct the history of water residence times in the Red Sea. We then use a hydraulic model of the water exchange between the Red Sea and the world ocean to derive the sill depth—and hence global sea level—over the past 470,000 years (470 kyr). Our reconstruction is accurate to within ±12 m, and gives a centennial-scale resolution from 70 to 25 kyr before present. We find that sea-level changes of up to 35 m, at rates of up to 2 cm yr-1, occurred, coincident with abrupt changes in climate.

Sea-level fluctuations during the last glacial cycle

A semi-empirical relation is presented that connects global sea-level rise to global mean surface temperature. It is proposed that, for time scales relevant to anthropogenic warming, the rate of sea-level rise is roughly proportional to the magnitude of warming above the temperatures of the pre–Industrial Age. This holds to good approximation for temperature and sea-level changes during the 20th century, with a proportionality constant of 3.4 millimeters/year per °C. When applied to future warming scenarios of the Intergovernmental Panel on Climate Change, this relationship results in a projected sea-level rise in 2100 of 0.5 to 1.4 meters above the 1990 level.

/pdf/a-semi-empirical-approach-to-projecting-future-sea-level-4dm059m0zo.pdf

A Semi-Empirical Approach to Projecting Future Sea-Level Rise

http://people.rses.anu.edu.au/lambeck_k/pdf/230.pdf

Sea-level and deep water temperature changes derived from benthic foraminifera isotopic records

The penultimate deglaciation: High-resolution paleoceanographic evidence from a north–south transect along the eastern Nordic Seas

Rapid climatic variability of the North Atlantic Ocean and global climate: a focus of the IMAGES program

The north Atlantic ocean is involved in the rapid climatic changes observed during glacial times. Indeed, many paleoclimatic indicators, from surface hydrological reconstructions, to deep water chemistry proxies, clearly indicate that major reorganizations of the Atlantic happened together with, and to some extent are probably responsible for the abrupt climatic shifts recorded in Greenland ice, but also in many marine and continental sites around the world.

Estelle Balbon

Papers

Sea-level and deep water temperature changes derived from benthic foraminifera isotopic records

The penultimate deglaciation: High-resolution paleoceanographic evidence from a north–south transect along the eastern Nordic Seas

Rapid climatic variability of the North Atlantic Ocean and global climate: a focus of the IMAGES program

Glacial and Interglacial Hydrological Changes in the North Atlantic Ocean