Reduced Arctic sea ice extent during the mid-Pliocene Warm Period concurrent with increased Atlantic-climate regime

Abstract

This is a repository copy of Reduced Arctic sea ice extent during the mid-Pliocene Warm Period concurrent with increased Atlantic-climate regime.

Enhanced Arctic Stratification in a Warming Scenario: Evidence From the Mid Pliocene Warm Period

“…However, the same orbitally paced control (e.g. eccentricity cycle) is observed in oceanic heat inflow into the Arctic (Rahaman et al., 2020). It suggests that enhanced inflow of NAC to the Arctic and the high relative nutrient utilization during warmer periods including MPWP follows the eccentricity cyclicity.…”

“… Comparison of relative nutrient utilization with sea surface temperature (SST), Atlantic water inflow, and sea ice extent. (a) δ 15 N record from ODP‐910C (present study) shows the relative nutrient utilization; (b) and (c) Authigenic ε Nd record and sea ice proxy (IP 25 ) with open water biomarker Highly Branched Isoprenoid III from 910C (Rahaman et al., 2020); (d) SST record from the ODP Site 982 (North Atlantic) using Alkenone UK 37 (Lawrence et al., 2009); (e) Atmospheric CO 2 concentration reconstructed using δ 11 B borate of G. ruber from ODP site 999, Caribbean Sea (de la Vega et al., 2020); (f) IRD record from the ODP Site 911A (Yermak Plateau, Knies et al, 2014); (g) LR04 stack of δ 18 O (‰) of benthic foraminifera (Lisiecki & Raymo, 2005). Dashed arrows show long term trend from 3.1 to 2.6 ma and solid arrow indicates glacial‐interglacial trends.…”

“…Another earlier study observed ice‐free summers, and probably a perennially ice‐free Arctic Ocean during the MPWP due to the inflow of warm Atlantic water into the Arctic Ocean through the Fram Strait (Cronin et al., 1993). A recent high‐resolution study from the same site (910C, Yermak Plateau) found less radiogenic neodymium isotope (low ε Nd ) during warmer periods of MPWP (Figure 4b) indicating a significant inflow of warm and saline Atlantic water into the Arctic (Rahaman et al., 2020). Comparison of ε Nd and δ 15 N org suggests that the enhanced NAC to the Arctic could have played a major role in strengthening the stratification which led to high relative nutrient utilization (Figures 4a and 4b).…”

“…The 507.4 m long sediment core was raised from 556.4 m water depth in the southern part of Yermak Plateau (80°15.896′N, 6°35.430′E) and out of which 199.2 -276.2 m is used in the present study pertaining to the late Pliocene. The chronology of the core is constructed using the tie points as given in Table 1 (Figure S2) and described in detail elsewhere (Rahaman et al, 2020). The age range of these samples is from 2.6 to 3.4 Ma that encompasses the MPWP.…”

“…Such an opportunity is presented by the Mid‐Pliocene Warm Period (MPWP, 3.264 – 3.025 Ma, million years ago; Dowsett et al., 2009; Dowsett et al., 2019; Haywood et al., 2020), which is the most recent such event when the conditions were similar to the present with similar CO 2 concentration (365 – 415 ppmv, Berends et al., 2019; Bartoli et al., 2011), a sea‐level higher by approximately 20 m than the present (Rohling et al., 2014), and annual mean surface temperature higher by 2.7°C – 4.0°C (Haywood et al., 2013). Earlier studies on MPWP have shown that the sea ice coverage at the Atlantic‐Arctic Gateway (AAG) region reduced considerably (Cronin et al., 1993; Rahaman et al., 2020). Other studies, though at a coarser resolution or spanning only a few glacial‐interglacial cycles, noted that the oceanic circulation/ventilation at the AAG reduced (enhanced) during colder (warmer) periods (Dowsett et al., 1992; Ravelo & Andreasen, 2000).…”