A Warmer Climate, Less Sea Ice, Sea Levels 5-16 Meters Higher Than Today An ‘Optimum’ For Penguins

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A new study (Gao et al., 2022) suggests Antarctica’s sea levels (Ross Sea) were more than 16 meters higher than today ~5,000 years ago and still 5.5 meters higher ~3,000 years ago. Penguins thrived with the warmer climate and diminished sea ice.

Image Source: Gao et al., 2022

“Since 1.5 kyr BP, with further contraction of the nesting areas the overall colony extent of Inexpressible Island decreased until 300 yr. BP, when the ACT zones were rapidly occupied. After 300 yr. BP the colony extent rapidly increased towards the present level (Fig. 5b). The overall colony extent exhibited a three-step increase, at 4.0-3.5 kyr BP, 3.0-2.0 kyr BP and ~1.5 kyr BP, respectively. After 1.5 kyr BP the colony extent slightly decreased but the low temporal resolution limits the inference about the modern age. One of the limitations of the RSL-derived approach is the assumption that penguins always occupied all the newly exposed areas in no more than 500 yr. as the sea level dropped and the occupation persisted for thousands of years toward present. Secondly, the RSL fall in the last 3000 yr. is as small as 5.5 m (Baroni and Hall, 2004). The slowdown of RSL fall prevents accurate age estimation.”

From ~7 to ~5 kyr BP, RSL [relative sea level] was above 16 m a. p.s.l. [above present sea level]”

Huang et al. (2009) also summarized that climate optimum conditions were commonly recorded between ~4.5 and 2.5 kyr BP from circum-Antarctica (Hodgson et al., 2004; Ingolfsson, 2004; Kirkup et al., 2002). For the Ross Sea region, studies have revealed that the mid-Holocene was a period of relatively warm and suitable climate, with elevated lake levels (Lyons et al., 1998) and well-developed microbial mats in the McMurdo Dry Valleys (Wagner et al., 2006), increased marine organic carbon deposition (Licht et al., 1998), and depleted d18O in carbonate shells from inshore regions (Emslie et al., 2003).”

Between ~4 and 3 kyr BP when coastal sea-ice was at a minimum, the Ross Sea experienced the “penguin optimum” (Baroni and Orombelli, 1994); between ~3 and 1.5 kyr BP when coastal sea-ice expanded, the Ross Sea penguin population declined sharply, and the Scott Coast was widely abandoned.”

via NoTricksZone

By Kenneth Richard on 26. May 2022