In-phase millennial-scale glacier changes in the tropics and North Atlantic regions during the Holocene

Abstract

Based on new and published cosmic-ray exposure chronologies, we show that glacier extent in the tropical Andes and the north Atlantic regions (TANAR) varied in-phase on millennial timescales during the Holocene, distinct from other regions. Glaciers experienced an early Holocene maximum extent, followed by a strong mid-Holocene retreat and a re-advance in the late Holocene. We further explore the potential forcing of TANAR glacier variations using transient climate simulations. Since the Atlantic Meridional Overturning Circulation (AMOC) evolution is poorly represented in these transient simulations, we develop a semi-empirical model to estimate the “AMOC-corrected” temperature and precipitation footprint at regional scales. We show that variations in the AMOC strength during the Holocene are consistent with the observed glacier changes. Our findings highlight the need to better constrain past AMOC behavior, as it may be an important driver of TANAR glacier variations during the Holocene, superimposed on other forcing mechanisms.

Moraines in the Austrian Alps record repeated phases of glacier stabilization through the Late Glacial and the Early Holocene

“…The link between the deglaciation of the Laurentide ice sheet, resulting in freshwater input into the North Atlantic, and cooling in Europe has been suggested as an explanation for abrupt centennial-scale cooling in the context of the YD-Holocene transition 61 , 62 . Moraine formation as a result of this teleconnection on the LG to Holocene time scale has recently been proposed by Young, et al 63 for the Greenland ice sheet, by Protin, et al 8 for mountain glaciers in the French Alps, by Braumann, et al 9 for the Austrian Alps, and by Jomelli, et al 64 for glaciers in the tropical Andes and the greater North Atlantic region. Comparing the warming during the pre-Bølling to Bølling transition and during the YD–Holocene transition (Fig.…”

Holocene glacial oscillations in the Tyroler Valley (NE Greenland)

“…Orbital‐induced reduced summer insolation in the Northern Hemisphere promoted a gradual cooling trend in Greenland from 8.2 ka onwards (McKay et al 2018). Superimposed on this long‐term trend, changes in the strength of the Atlantic Meridional Overturning Circulation and other regional forcing mechanisms affected glacial dynamics: ice masses of the North Atlantic region generally retreated significantly during the mid‐Holocene and re‐advanced in the late Holocene (Jomelli et al 2022). Summer temperatures fell until 1–1.5 °C below present‐day temperatures by the end of the mid‐Holocene, albeit with a high degree of variability across Greenland (Lasher and Axford 2019).…”

“…Local mountain glaciers and ice caps recorded a similar response pattern to the GrIS to changing Holocene climate trends. In S Greenland most of the glaciers disappeared between 7.1 and 5.5 ka and began to recover from 3.1 ka to 1.3 ka onwards (Larocca et al, 2020a; Jomelli et al 2022). In SW Greenland, some glaciers survived throughout the HTM and began to recover from 4.3 ka onwards (Larocca et al, 2020b).…”

“…The Little Ice Age (LIA; ca. 1300–1850 CE; Grove, 2001) was the last period with documented widespread glacial expansion in NE Greenland (Kjær et al 2022), as demonstrated by the direct dating of glacial records by means of cosmic‐ray exposure (CRE) dating (Biette et al 2020; Garcia‐Oteyza et al 2022; Jomelli et al 2022) or even by historical pictures provided by early travellers or hunters that show glaciers larger than those of the present during the late 19th and early 20th centuries in this region (Boyd 1948; Payer 1876).…”

“…11.3 and 10.8 ka and minor Holocene glacial advances at ca. 3.3, 1.2, and 0.4 ka (Clavering Island; Biette et al 2020; Jomelli et al 2022).…”