6.1. Rapid Climate Changes and Surface Water Mass Variability
 The periods covering the MIS 15–MIS 9 (580–300 ka) and the MIS 1 (15–0 ka), recorded in core MD03-2699, are characterized by a general trend of warm and relative stable interglacial periods which contrast with high-frequency variability during glacial inceptions and glacials (Figure 3). The transition from relatively stable interglacials to unstable glacial conditions occur when the benthic threshold value for ice sheet instability was passed, coinciding with the increase of continental ice volume [McManus et al., 1999], higher-amplitude changes in Antarctica, and decrease of greenhouse gas concentrations (Figures 3 and 6).
Figure 6. Iberian Margin sea surface record for the last 580 kyr in comparison to paleoarchive records over the last six climate cycles. (a) The eccentricity, (b) the obliquity, and (c) the precession of the Earth's orbit [Berger, 1978] are external triggers of the climate system. (d) Daily insolation at 37°N during the summer solstice. (e) Spliced alkenone-based SST records of cores MD01-2443 and MD01-2444 [Martrat et al., 2007] and of core MD03-2699 (this study). (f) Benthic δ18O LR04 stack [Lisiecki and Raymo, 2005]. (g) EDC CO2 greenhouse gas concentrations [Siegenthaler et al., 2005]. (h) Temperature (°K) profile of the EPICA Dome C ice core (EDC) [Jouzel et al., 2007] with the marine isotopic stages (MIS). Gray bands mark terminations, and the dashed horizontal lines indicate Holocene levels.
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 Superimposed on the glacial-interglacial oscillations, suborbital millennial-scale climate variability was detected in the western Iberian Margin (Figure 3). Thus, we have identified 21 cold, stadial-type SST oscillations. Five occurred during the interval from MIS 15.1 to MIS 14, eight during MIS 13–MIS 12 and finally, eight during MIS 11–MIS 10 (Figure 3e), suggesting that the SST shifts were more frequent during the more recent climatic cycles (Figure 6). Some of these events were extremely cold and probably associated with episodes of iceberg melting in the western Iberian Margin, as demonstrated by the extreme cold SST values, the highest tetraunsaturated alkenone percentages and sometimes by the presence of IRD rich layers in core MD03-2699 (Figures 3c, 3d, and 3e). These events are similar in their general trends to those detected in the midlatitudes of the eastern North Atlantic during the last glacial period, known as Heinrich events [de Abreu et al., 2003; Bard et al., 2000; Eynaud et al., 2009; Martrat et al., 2007; Naughton et al., 2009; Pailler and Bard, 2002; Voelker et al., 2006]. We therefore associated the extreme cold phases occurring between 580 and 300 ka (MIS 15–9) with Heinrich-type events. It is also known that during Heinrich events extreme SST coolings and reduction in Atlantic Meridional Overturning Circulation (AMOC) favored the southward displacement of the Polar Front down to the midlatitudes of the North Atlantic [López-Martínez et al., 2006; Naughton et al., 2009; Voelker et al., 2006; Eynaud et al., 2009].
 Regarding in detail alkenone-based SST records from the western Iberian Margin (MD01-2444 [Martrat et al., 2007]; MD95-2042, MD95-2040 [Pailler and Bard, 2002]; and MD99-2331 [Naughton et al., 2009]) that cover the last glacial period we observe a gradual pattern of SST decrease from south to north during Heinrich events. Salgueiro et al.  based on foraminifera-derived summer SST, also detected the same latitudinal gradient pattern along the Iberian Margin and demonstrated that the northern Iberian Margin was more affected by the subpolar water masses than the southern part which was more influenced by the subtropical water masses from the Azores current. Core MD03-2699 is located at or close to the boundary between these areas and being affected by both water masses. The study area is therefore highly sensitive to the water mass fluctuations and changes in the position of the subtropical and subpolar hydrographic fronts that occurred in the past.
 We identified eight Heinrich-type (Ht) events between 580 and 300 ka (MIS 15–9) in core MD03-2699 (Figure 3). Ht8 was detected during the glacial inception of MIS 14 and is marked by a drop of SST down to 12°C (reaching values colder than those recorded during the glacial MIS 14) and high percent of C37:4 (Figures 3d and 3e). This suggests that during this event the Polar Front reached the southern Iberian Margin favoring the advection of subpolar waters into the study area. Ht7 (within MIS 12) was the coldest event detected within pleniglacial periods and shows high %C37:4 (Figure 3) suggesting therefore that the studied area was mainly under the influence of subpolar waters. During Ht6 (within MIS 12), the subtropical water masses had, probably, a strong influence on the site because the SST were not as cold and the %C37:4 not so high as that characterizing the previous Ht events (Figure 3). The core site also seems to have been highly influenced by the subpolar waters during Ht5 (MIS 12.2). Ht4 is the most extreme cold event detected between MIS 15 and MIS 9 and occurred at the beginning of Termination V (Figure 3). This event is however, complex and composed of three phases: two coolings separated by a warming (Figure 4). The first phase is marked by a drastic SST drop and, extremely high percentages of C37:4; the second by an increase of SST of about 4°C and a decrease of %C37:4 and the third phase is characterized by the returning to cold conditions, high %C37:4 and high IRD content. This suggests that during both the first and third phases of Ht4 the Polar Front was probably displaced south of 39°N and therefore the studied area was mainly under the influence of the subpolar water masses and, that during the second phase of Ht4 the Polar Front was slightly displaced further north. A similar complex pattern was recorded in the Iberian Margin during extreme cold events within the last glacial period and last glacial-interglacial transition [Bard et al., 2000; Martrat et al., 2007; Naughton et al., 2009; Rodrigues et al., 2010; Voelker et al., 2006] being associated to changes in the position of the Polar Front. During Ht3 and Ht2 (within the glacial inception of MIS 10) the subtropical water masses probably affected the hydrological conditions at the study site again as cooling was less pronounced. Finally, the youngest Ht event recorded in core MD03-2699, is Ht1. This event occurred during Termination IV and is marked by a SST decrease down to 12°C, moderate percent of C37:4 and virtual absence of IRD (Figures 3 and 4). This suggests that besides the influence of subpolar water masses, as revealed by the %C37:4, the studied area was probably also affected by the advection of subtropical water masses.
 Similar events, characterized by the deposition of high quantities of IRD, were identified in the IODP Site U1313 record, based on the dolomite content analysis (reflecting a Canadian source of icebergs) [Stein et al., 2009]. However, it is possible that some of these Heinrich type layers had a main contribution from the European ice sheets rather than the Laurentide ice shield [Stein et al., 2009]. Two of these Heinrich-type episodes, identified in the Iberian Margin record (MD03-2699) as Ht2 and Ht3, coincided with two extreme events, marked by IRD peaks and extreme sea surface coolings (% N. pachyderma peaks), noticed for ODP Site 980, located close to the British ice sheet (Figures 1 and 3d) [McManus et al., 1999; Oppo et al., 1998]. These episodes occurred also in synchrony with episodes of substantial iceberg discharges recorded at IODP Site U1308 (Figure 1), also located close to the British ice sheet [Hodell et al., 2008]. Far away from the British ice sheet, IODP Site U1313 [Stein et al., 2009] (Figure 1) did not detect the presence of IRD layers during Ht2 and Ht3. Thus, only the records located next to the British ice sheets are characterized by IRD deposition, suggesting that the British ice sheet was probably the main source of IRD and freshwater during the Ht2 and Ht3. One additional Ht event than those recorded in core MD03-2699 was detected in IODP Site U1313 at around 355 ka [Stein et al., 2009], but it did not have a great impact on the SST decrease in the western Iberian Margin.
 Ht events are also imprinted in the continental biomarkers records of MD03-2699 between MIS 15 and MIS 9 (Figures 5d and 5e). During most of the Ht events (Ht7 to Ht1), the terrigenous biomarkers' concentrations were very low (Figures 5d and 5e). The decrease of terrigenous biomarkers concentrations in marine sediments can be due to (1) changes in the prevailing wind patterns from easterlies to westerlies which preclude the transfer of cuticles from vascular plants to the sea and/or (2) temperate forest contraction in the neighboring continent. It is known that during last glacial Heinrich events the westerly prevailing winds preclude the transfer of high quantities of sediment into the deep sea [Sánchez Goñi et al., 2002]. One could speculate that those environmental conditions had also prevailed during the previous Ht events within the MIS 15–MIS 9 interval. Also, the decrease of terrigenous biomarkers concentrations during Ht3 and Ht2 in the western Iberian Margin were contemporaneous with the two episodes of temperate and humid forest reduction in the Iberian Peninsula over MIS 11.23 and 11.24 [Desprat et al., 2007] and increase of ice volume as documented by the benthic δ18O [de Abreu et al., 2005; Tzedakis et al., 2003].
 The marine productivity inferred from the total alkenones concentration and TOC content of core MD03-2699 was very low during most Ht events (Ht7 to Ht1) (Figure 5b). Reduced productivity was also noticed for the last glacial Heinrich events in the northwestern Iberian Margin [Salgueiro et al., 2010] and in the open North Atlantic and Norwegian Sea [Nave et al., 2007]. A contrasting pattern has been detected during Ht8 which reveals high concentration of continental biomarkers and substantial marine productivity (Figures 5b and 5c) suggesting that exceptional environmental conditions associated with prevailing easterlies favored the input of continental nutrients into the ocean.
 In order to compare the suborbital climate variability detected in core MD03-2699, between 580 and 300 ka, with that characterizing more recent climatic cycles we combine our SST-U37k′ data with that of MD01-2443 [Martrat et al., 2007]. The spliced SST-U37k′ profile of cores MD03-2699 and MD01-2443 clearly shows that suborbital-scale climate variability occurred in the Iberian Margin as far back in time as the sixth Pleistocene climate cycle (Figures 6 and 7). The SST-U37k′ record of core MD03-2699 overlaps that obtained in core MD01-2443 between MIS 11 and the mid-MIS 9 (Figures 6 and 7) and extends it further back in time until the end of MIS 15. Both records show the same pattern during the overlapping period and similar SST values during interglacial optimums. However, they do not show either the same SST values or amplitude of SST fluctuations within MIS 10 and late MIS11 (Figure 6). SST was a few degrees colder and the amplitude of suborbital oscillations was higher in the southernmost core (MD01-2443) than in core MD03-2699. This suggests that site MD01-2443 might have experienced of stronger upwelling conditions reflected by colder SST than at site MD03-2699.
Figure 7. Zooming in the Iberian Margin alkenone-based SST records for the last 600 ka. Direct comparison of the interglacial temperature profiles.
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 The composed Iberian Margin SST record (Figures 6 and 7) reveals that colder SSTs were recorded during MIS 8 than during MIS 12, even though the ice volume was higher during the latter glacial. This composed record also shows that the pattern of the last deglaciation (two cold phases coincided with Heinrich event 1 and Younger Dryas separated by a warming episode, the Bølling-Allerød) also occurred during deglaciations of MIS 8 and MIS 6 (Figures 6 and 7). The abrupt climatic shifts of those deglaciations were likely the result of changes in the position of the Polar Front and can be traced back at least to Termination V. This suggests that the deglacial pattern changed after the Mid-Brunhes event, associated with variations in the climate forcing.
 Glacial MIS 14 was warmer (14°C) than any of the later glacials (Figure 6), in agreement with what has been recorded in other regions, such as in North Atlantic (ODP Site 982 [Wright and Flower, 2002]), the subtropical North Atlantic (ODP Site 1058 [Billups et al., 2006]), off northwest Africa (ODP Site 658 [Eglinton et al., 1992]), the southeast Atlantic Ocean [Chen et al., 2002], and the eastern equatorial Pacific (ODP Site 849 [Mix et al., 1995]). Voelker et al.  suggest that a different circulation pattern was probably in place during this glacial period and that the subtropical waters of the Azores current had a substantial influence on the Iberian Margin. Also, both the terrestrial input and marine productivity were higher and different from what has been recorded in other glacial periods (Figures 5c, 5d, and 5e) supporting the idea that different circulation patterns prevailed during MIS 14.
 The transition of MIS12 to MIS11 and MIS 10 to MIS 9 is very similar reflecting the increase in biomarker concentrations contemporaneous with warmer SST, especially during the deglaciation, followed by an abrupt decline during the warm conditions and a gradual increase to the next glacial period. The transition of MIS 14 to MIS 13 is similar in their general trends to MIS12-MIS11 and MIS 10-MIS 9 deglaciations, with an abrupt increase of biomarker concentrations during the termination. However, biomarker concentrations remained high during most of MIS 13 before declining early in MIS 12. During the later MIS 12 the biomarker concentrations and thus productivity oscillated, in a similar way as during MIS 14, but maxima of MIS 12 and 14 only reached values as high as the late MIS 13.1 and never those from MIS 10 (Figures 5c, 5d, and 5e). This clearly indicates that climatic conditions such as the wind conditions reflected by the terrigenous biomarkers were different prior and after the mid-Brunhes event. The high productivity during MIS 13, i.e., during 54 ka, and the SST values lower than the more recent interglacial periods, could help explain the lower atmospheric CO2 concentrations during MIS 13, in particular because also the planktonic foraminiferal δ13C data imply lower nutrient concentrations or high nutrient consumption (high δ13C values [Voelker et al., 2009]).
 In general, the total concentration of biomarker compounds in the marine sediments is characterized by low content during glacial periods and increased during the deglaciations (Figure 5).
 Within the chronological constraints the millennial-scale oscillations observed during glacials (MIS 14, 12 and 10) and glacial inceptions, appear to have counterparts in the EPICA δD record where the same number of cooling events for each glacial interval is also identifiable (Figures 3 and 6). However, event Ht8 was very likely contemporary with the subsequent Antarctic major warming event labeled 14.3 in the work by Jouzel et al.  and not with the cold phase like it is with the current age model. If this is true, it is consistent—in agreement with the response of Ht 4 as well—with the last ice age observation for the Greenland interstadials duration being correlated with the Antarctica warming amplitude [EPICA Community Members, 2004].
6.2. Interglacial Climate Conditions
 Interglacial periods, i.e., MIS 9.3, MIS 11.3, MIS 13.3 and 13.1, are detected in the SST profile of core MD03-2699 (Figure 7). Interglacial MIS 9.3 is warmer than the present interglacial in agreement with what has been noticed in other records from the Iberian Margin [Desprat et al., 2007; Martrat et al., 2007] and by the EPICA ice core temperature record [Jouzel et al., 2007]. Our SST record, however, also highlights that the interglacials prior to MIS 9.3 lasted longer and had more stable mean annual surface temperatures. Interglacials following Terminations IV and VI are marked by an abrupt SST increase which parallels the increase of Northern Hemisphere summer insolation while that of Termination V occurred during the maximum of insolation (Figure 4).
 MIS 13, was a long, relative warm period experiencing some small-scale oscillations and was 2°C colder than the subsequent interglacial period. The two more stable interglacial periods, marked by the absence of C37:4 alkenones, lasted 5 ka and occurred during MIS13.3 (around 510 ka) and MIS 13.1 (around 495 ka). However, only small SST variations were recorded for a period of about 54 ka making MIS 13 the longest interglacial for the last 580 ka, at least on the Iberian Margin. MIS 13 is also characterized by relatively low δ18O values indicating a lower sea level than during the subsequent interglacials and maximum δ13C levels both at the surface and in the deep ocean [Hodell et al., 2003; Lisiecki and Raymo, 2005]. In the Southern Hemisphere the existing data indicates cooler Antarctic temperatures [Jouzel et al., 2007], lower CO2 and CH4 concentrations [Lüthi et al., 2008; Siegenthaler et al., 2005], and lower summer sea surface temperatures in the South Atlantic [McClymont et al., 2005]. Conditions that coincided with extremely strong Asian, Indian and African summer monsoons, weakest Asian winter monsoon and lowest Asian dust and iron fluxes [Guo et al., 2009]. Pervasive warm conditions were also evidenced by the records from the Asian monsoon zone [Yin and Guo, 2007] and the northern high-latitude regions [de Vernal and Hillaire-Marcel, 2008]. Accordingly, Guo et al.  conclude that a strong asymmetry of hemispheric climates existed during MIS 13 with a warmer Northern Hemisphere and a cooler Southern Hemisphere. Nevertheless, our record in the Iberian Margin shows a MIS 13 cooler than the subsequent interglacials contrarily to this recent consideration (Figures 6 and 7).
 The warmest phase of MIS 11, MIS 11.3, lasted 30 ka on the Iberian Margin and was synchronous with the major forest expansion episodes documented for the northwestern Iberian Peninsula [Desprat et al., 2005, 2007]. During this interval, maximum SSTs of 18°C were interrupted by a short cooling event (1°C) around 412 ka (Figure 3). A similar pattern was registered in core MD01-2443, south of MD03-2699, and at the midlatitude North Atlantic IODP Site U1313 (Figure 3). At the latter site the minimum between the two plateaus within MIS 11.3 occurred at 413 ka and was more pronounced probably due to more variable conditions in the western North Atlantic and admixing of subpolar surface waters at that time [Stein et al., 2009; Voelker et al., 2009]. On the other hand, IODP Site U1313 shows a temperature maximum of 19°C during MIS 11.3 related to the stronger influence of the Gulf Stream/North Atlantic Drift at the site.
 The pattern reflected by the terrigenous biomarkers during MIS 11, with maxima during the early phase, is similar to the dust record off northwestern Africa, ODP Site 958 [Helmke et al., 2008]. Thus, the strengthening of the trade winds over northwestern Africa occurred synchronously with the increase of terrestrial input in the western Iberian Margin suggesting also a strengthening of the westerly winds in that region. The strong northerly winds led to a higher nutrient availability, either through upwelling or as continental coastal input, and thus to an increase in coccolithophores production as reflected by the higher concentration of total alkenones during the early phase of MIS 11.3. The total biomarker concentration started to decline with the onset of the humid period in Africa, that is before the first SST plateau ended, indicating that the shift in atmospheric circulation over Africa also impacted Iberia.
 In general terms MIS 11.3 and MIS 9.3 show similar conditions, but a major difference is noted in the ventilation of the surface to subsurface water masses and their impact on the meridional overturning circulation [Voelker et al., 2009]. This difference is corroborated by the MD03-2699's SST and biomarker signals during MIS 9.3 when productivity decreased earlier than in the previous interglacials (Figure 5). In detail, the MIS 9.3 SST record reveals a warmer interval at the beginning of the interglacial with temperatures close to 20°C, i.e., 2°C warmer than during MIS 11.3, followed by a decreasing trend associated with millennial-scale variability of 2°C in amplitude during the second half of MIS9.3 until 320 ka (Figure 7) and prior to the onset of the next glacial inception that started with stadial MIS 9.2. The productivity increase was contemporary with maxima in the terrigenous markers suggesting that, as during the early MIS 11.3, stronger winds and an additional supply of nutrients from the continent sustained the productivity near the studied site (Figure 4). The productivity patterns observed in core MD03-2699 differ from those recorded at IODP Site U1313, where productivity during interglacials was minimal and high during the glacial periods [Stein et al., 2009] highlighting the different responses of open ocean productivity (U1313) and upwelling-related productivity (MD03-2699) to the respective climate forcing.
6.3. Holocene Versus MIS 11
 The parallelism of the climate evolution between MIS 11.3 and the Holocene is not straightforward and extrapolations of past to present conditions leads to different perspectives on the length of the current interglacial depending on which parameter is used for chronological alignment [Tzedakis, 2009]. Synchronization according to precession shows that the present day should be analog to MIS 11 at 398 ka [Loutre and Berger, 2003]. In contrast, synchronization based on obliquity, i.e., Terminations I and V, shows that present day would correspond to 407 ka in MIS 11 [EPICA Community Members, 2004; Masson-Delmotte et al., 2006].
 In the composed Iberian SST records for the last sixth climate cycles (Figures 6 and 7) the warmer interglacials were MIS 5.5 (Eemian) with 21°C, followed by MIS 9.3 (20°C) and MIS 7.5 (19°C), while maximum temperatures during MIS 11.3 (18°C) were similar to SST values found for the Holocene (Figure 7). This observation is not surprising because the orbital parameters of MIS 11.3 and the present interglacial, the Holocene, are also rather similar. Eccentricity was at minimum during MIS 11 and in the Holocene while insolation at 65°N and precession were similar as well. Sea level reconstructions based on benthic δ18O values suggest that sea level 410 ka ago was also at a level similar to the one reached 10 ka ago (Figure 6).
 Holocene maximum SST values, close to 19°C, occurred between 10.5 and 9.7 ka while the MIS 11.3 record reveals two warmer phases: the first with maximum SST close to 18°C (427 to 412 ka) and a second with temperatures close to 19°C (407 to 395 ka). Both periods display a SST decrease following the maximum temperature values. However, in the case of MIS 11 that decreases was interrupted by the second SST increase along with the sea level highstand. A long-term decrease of 1.5°C in SST, is also similar in both periods at the Estremadura site MD03-2699 implying that the SST record of the first part of MIS 11 (427 to 412 ka) and the last 10.5 ka record reflect similar hydrographic conditions during both periods. In terms of duration of the two interglacials, the fact that interglacial duration changed toward shorter periods after the Mid-Brunhes event prevents further estimations.