What Ends an Interglacial? Feedbacks Between Tropical Rainfall, Atlantic Climate and Ice Sheets During the Last Interglacial - Integrated Analysis of Interglacial Climate Dynamics (INTERDYNAMIC) - page 27

River, exert a strong in N. Today, the North Brazil

Current (NBC) carries Amazon freshwater towards the Caribbean Sea. However,
the NBC retro

uence on the signal at 12 °

ects up to 70 % of the Amazon plume eastward between
July and December (Lentz 1995 ). In a way similar to cold episodes of the last 30 ka
(Wilson et al. 2011 ), we propose that

ection de

the NBC retro ection was seasonally

intensi ecting oceanward the

plume of Amazon freshwater. Such changes would explain the relative decrease in
Amazon material recorded around 119 ka BP at 12

ed or prolonged in duration at the end of the LIG, de

° N (Fig. 2 d), despite increasing

Amazon River discharge. The enhanced NBC retro ection simulated by the climate

model (Fig. 1 d) at 115 ka BP compared to 125 ka BP supports this hypothesis
(Wilson et al. 2011 ). Our experiments isolating the impact of river runoff show that
the 16 % increase in Amazon river discharge contributed to the plume of decreased
SSS in the tropical Atlantic (Fig. 1 e). As a result of the fresher North Atlantic, the
position of the North Atlantic Deep Water formation region is shifted southward
(Fig. 1 f), inducing a signi cant (p < 0.05) 4 % decrease in deep water formation.

This change in North Atlantic salinity and circulation led to changes in sea-surface
temperatures (not shown), which may impact Northern hemisphere atmospheric
circulation and ice sheet inception at the end of the LIG.
In summary, our model-data comparison indicates substantial shifts in South
American hydrologic cycle and upper tropical Atlantic salinities that may impact
the THC and North Atlantic climate at the end of the LIG.

References

Bakker P, Stone EJ, Charbit S, Gr ger M, Krebs-Kanzow U, Ritz SP, Varma V, Khon V, Lunt DJ,

Mikolajewicz U, Prange M, Renssen H, Schneider B, Schulz M (2013) Last interglacial
temperature evolution

ö

— a model inter-comparison. Clim Past 9(2):605 - 619. doi: 10.5194/cp-9-

605-2013
Cheng H, Sinha A, Cruz FW, Wang X, Edwards RL, d Horta FM, Ribas CC, Vuille M, Stott LD,

Auler AS (2013) Climate change patterns in Amazonia and biodiversity. Nat Commun 4:1411.
doi: 10.1038/ncomms2415
Govin A, Chiessi CM, Zabel M, Sawakuchi AO, Heslop D, H ö rner T, Zhang Y, Mulitza S (2014)
Terrigenous input off northern South America driven by changes in Amazonian climate and the
North Brazil current retro ection during the last 250 ka. Clim Past 10:843 - 862. doi: 10.5194/
cp-10-843-2014
Guyot JL, Jouanneau JM, Soares L, Boaventura GR, Maillet N, Lagane C (2007) Clay mineral
composition of river sediments in the Amazon Basin. Catena 71(2):340

'

- 356. doi: 10.1016/j.

catena.2007.02.002
Krebs U, Timmermann A (2007) Tropical air-sea interactions accelerate the recovery of the
atlantic meridional overturning circulation after a major shutdown. J Clim 20(19):4940 - 4956.

doi: 10.1175/jcli4296.1
Lentz SJ (1995) Seasonal variations in the horizontal structure of the Amazon Plume inferred from
historical hydrographic data. J Geophys Res Oceans 100(C2):2391 - 2400. doi: 10.1029/

94jc01847
Tzedakis PC, Channell JET, Hodell DA, Kleiven HF, Skinner LC (2012) Determining the natural
length of the current interglacial. Nat Geosci 5(2):138 - 141. doi: 10.1038/ngeo1358