A global mean sea-surface temperature dataset for the Last Interglacial (129–116 kyr) and contribution of thermal expansion to sea-level change

Abstract

Abstract. A valuable analogue for assessing Earth’s sensitivity to warming is the Last Interglacial (LIG; 129–116 kyr), when global temperatures (0−+2 °C) and mean sea level (+6–11 m) were higher than today. The direct contribution of warmer conditions to global sea level (thermosteric) are uncertain. We report here a global network of LIG sea surface temperatures (SST) obtained from various published temperature proxies (e.g. faunal/floral assemblages, Mg/Ca ratios of calcareous plankton, alkenone UK’37). Each reconstruction is averaged across the LIG (anomalies relative to 1981–2010), corrected for ocean drift and with varying seasonality (189 annual, 99 December-February, and 92 June–August records). We summarise the current limitations of SST reconstructions for the LIG and the spatial temperature features of a naturally warmer world. Because of local δ18O seawater changes, uncertainty in the age models of marine cores, and differences in sampling resolution and/or sedimentation rates, the reconstructions are restricted to mean conditions. To avoid bias towards individual LIG SSTs based on only a single (and potentially erroneous) measurement or a single interpolated data point, here we average across the entire LIG. To investigate the sensitivity of the reconstruction to high temperatures, we also report maximum values during the first 5 ka of the LIG (129–124 kyr). The global dataset provides a remarkably coherent pattern of higher SST increases at polar latitudes than in the tropics, with comparable estimates between different SST proxies. We report mean global annual SST anomalies of 0.2 ± 0.1 °C and a maximum of 0.9 ± 0.2 °C respectively. Using the reconstructed SSTs suggests a mean thermosteric sea level rise of 0.01 ± 0.1 m and a maximum of 0.13 ± 0.1 m respectively. The data provide an important natural baseline for a warmer world, constraining the contributions of Greenland and Antarctic ice sheets to global sea level during a geographically widespread expression of high sea level, and can be used to test the next inter-comparison of models for projecting future climate change. The dataset described in this paper, including summary temperature and thermosteric sea-level reconstructions, are available at https://doi.org/10.1594/PANGAEA.904381 (Turney et al., 2019).

How does the Southern Ocean palaeoenvironment during Marine Isotope Stage 5e compare to the modern?

“…Diatoms are phototrophic algae, which are prevalent in the SO euphotic zone, and their species distribution patterns are closely related to the environmental conditions in the surface waters, principally the sea ice cover and SSTs (Zielinski & Gersonde 1997, Gersonde & Zielinski 2000, Esper et al 2010. Several previous studies have used marine sediment core records to reconstruct the palaeoceanographic conditions during MIS 5e, often alongside model simulations (Bianchi & Gersonde 2002, Turney & Jones 2010, Otto-Bliesner et al 2013, Capron et al 2014, Hoffman et al 2017, Turney et al 2020. However, these studies contain few, or no, marine records from south of 55 o S and therefore are unable to capture the MIS 5e environmental conditions in the Antarctic Zone (south of the Polar Front).…”

Global River Discharge and Floods in the Warmer Climate of the Last Interglacial

“…Atmospheric surface temperatures were higher than the preindustrial (PI) period and probably slightly higher than the present, with largest anomalies in the Northern Hemisphere and particularly at its high latitudes (CAPE Members, 2006;Turney & Jones, 2010); however, global quantifications are still inadequate (Capron et al, 2017). Global estimates of LIG sea surface temperature anomalies compared to the present range between 0°C and +0.9°C (Hoffman et al, 2017;Turney et al, 2020) and mean ocean temperature anomaly is estimated to be approximately +1°C (Shackleton et al, 2020). The warmth of the LIG was due to the different latitudinal distribution of seasonal insolation and the resulting internal climate feedbacks, principally related to Arctic amplification of warming.…”

“…The warmth of the LIG was due to the different latitudinal distribution of seasonal insolation and the resulting internal climate feedbacks, principally related to Arctic amplification of warming. The LIG has been abundantly studied in terms of temperature, using climate models (e.g., Lunt, Abe-Ouchi, et al, 2013;Otto-Bliesner et al, 2013 and with proxies covering some Northern Hemisphere continents and many ocean subbasins (Capron et al, 2017;Hoffman et al, 2017;Turney et al, 2020), and recently also in terms of precipitation (Nikolova et al, 2013;Pedersen et al, 2017). In particular, the higher boreal LIG precipitation likely resulted from high-latitude warming and associated reduction in boreal latitudinal temperature gradients, ultimately linked to differences in insolation (Scussolini et al, 2019).…”

Global River Discharge and Floods in the Warmer Climate of the Last Interglacial

“…The warmth of the LIG was due to the different latitudinal distribution of seasonal insolation and the resulting internal climate feedbacks, principally related to Arctic amplification of warming. The LIG has been abundantly studied in terms of temperature, using climate models (e.g., Lunt, Abe‐Ouchi, et al, 2013; Otto‐Bliesner et al, 2013, 2020) and with proxies covering some Northern Hemisphere continents and many ocean subbasins (Capron et al, 2017; Hoffman et al, 2017; Turney et al, 2020), and recently also in terms of precipitation (Nikolova et al, 2013; Pedersen et al, 2017). In particular, the higher boreal LIG precipitation likely resulted from high‐latitude warming and associated reduction in boreal latitudinal temperature gradients, ultimately linked to differences in insolation (Scussolini et al, 2019).…”

“…Atmospheric surface temperatures were higher than the preindustrial (PI) period and probably slightly higher than the present, with largest anomalies in the Northern Hemisphere and particularly at its high latitudes (CAPE Members, 2006; Turney & Jones, 2010); however, global quantifications are still inadequate (Capron et al, 2017). Global estimates of LIG sea surface temperature anomalies compared to the present range between 0°C and +0.9°C (Hoffman et al, 2017; Turney et al, 2020) and mean ocean temperature anomaly is estimated to be approximately +1°C (Shackleton et al, 2020). The warmth of the LIG was due to the different latitudinal distribution of seasonal insolation and the resulting internal climate feedbacks, principally related to Arctic amplification of warming.…”