Rapid sea-level rise and reef back-stepping at the close of the last interglacial highstand

Abstract

Widespread evidence of a +4-6-m sea-level highstand during the last interglacial period (Marine Isotope Stage 5e) has led to warnings that modern ice sheets will deteriorate owing to global warming and initiate a rise of similar magnitude by ad 2100 (ref. 1). The rate of this projected rise is based on ice-sheet melting simulations and downplays discoveries of more rapid ice loss. Knowing the rate at which sea level reached its highstand during the last interglacial period is fundamental in assessing if such rapid ice-loss processes could lead to future catastrophic sea-level rise. The best direct record of sea level during this highstand comes from well-dated fossil reefs in stable areas. However, this record lacks both reef-crest development up to the full highstand elevation, as inferred from widespread intertidal indicators at +6 m, and a detailed chronology, owing to the difficulty of replicating U-series ages on submillennial timescales. Here we present a complete reef-crest sequence for the last interglacial highstand and its U-series chronology from the stable northeast Yucatán peninsula, Mexico. We find that reef development during the highstand was punctuated by reef-crest demise at +3 m and back-stepping to +6 m. The abrupt demise of the lower-reef crest, but continuous accretion between the lower-lagoonal unit and the upper-reef crest, allows us to infer that this back-stepping occurred on an ecological timescale and was triggered by a 2-3-m jump in sea level. Using strictly reliable (230)Th ages of corals from the upper-reef crest, and improved stratigraphic screening of coral ages from other stable sites, we constrain this jump to have occurred approximately 121 kyr ago and conclude that it supports an episode of ice-sheet instability during the terminal phase of the last interglacial period.

Last interglacial temperature seasonality reconstructed from tropical Atlantic corals

“…These modelling efforts reveal that the mid-LIG increased SST seasonality in the Caribbean Sea results primarily from summer warming, contrary to the conclusion reached in Winter et al (2003). Our coral Sr/Ca records and time-slice simulations also further substantiate the transient modelling and hosing experiments (Felis et al, 2015) that demonstrate the insensitivity of tropical SST seasonality to the wider climate instabilities that perturbed the Atlantic realm during the LIG (Sirocko et al, 2005;Blanchon et al, 2009;O'Leary et al, 2013;Galaasen et al, 2014;Mokeddem et al, 2014). In summary, our results affirm the prevailing influence of orbital insolation changes on tropical SST seasonality.…”

“…The LIG was punctuated by profound changes and instabilities. However, as demonstrated by a water hosing experiment performed on model simulations of LIG climate and a coral proxy record (Felis et al, 2015), temperature seasonality in the tropical Atlantic was relatively insensitive to the influences of monumental ice sheet loss (Blanchon et al, 2009), sea level rise (O'Leary et al, 2013), rapid reorganisation of oceanic currents (Galaasen et al, 2014), cold events (Mokeddem et al, 2014) and abrupt climatic shifts (Sirocko et al, 2005).…”

Comment on “MIS 5a and MIS 3 relatively high sea-level stands on the Hatay-Samandağı coast, Eastern Mediterranean, Turkey”. U. Doğan, A. Koçyiğit, B. Varol, İ. Özer, A. Molodkov, E. Zöhra. Quaternary International (2012), 262, 65–79

“…(4) There is a broad-scale consensus over the timing and the elevation of the Last Interglacial (MIS 5e) sea-level. During this time period, sea-level was several meters higher than that of today (w4 AE 2 m apsl) and the start of MIS 5e high stand has been dated to w128 ka BP in tectonically stable sites (Chen et al, 1991;Stirling et al, 1995Stirling et al, and, 1998McCulloch and Esat, 2000;Muhs, 2002;Blanchon et al, 2009). Therefore, in tectonically uplifting areas, in order to determine vertical tectonic uplift rates, the elevation and the age of MIS 5e coastlines are used.…”

A New Early Miocene (Aquitanian) Elasmobranchii Assemblage from the la Guajira Peninsula, Colombia

“…However, such resilience will deeply depend on the rate of rise (Hamylton et al, 2014). A rapid sea-level increase will produce a collapse of the reef system (Blanchon et al, 2009;Done, 2011;Hamylton et al, 2014).…”